Provided by: valgrind_3.15.0-1ubuntu9.1_amd64 bug


       valgrind - a suite of tools for debugging and profiling programs


       valgrind [valgrind-options] [your-program] [your-program-options]


       Valgrind is a flexible program for debugging and profiling Linux executables. It consists
       of a core, which provides a synthetic CPU in software, and a series of debugging and
       profiling tools. The architecture is modular, so that new tools can be created easily and
       without disturbing the existing structure.

       Some of the options described below work with all Valgrind tools, and some only work with
       a few or one. The section MEMCHECK OPTIONS and those below it describe tool-specific

       This manual page covers only basic usage and options. For more comprehensive information,
       please see the HTML documentation on your system:
       $INSTALL/share/doc/valgrind/html/index.html, or online:


       The single most important option.

       --tool=<toolname> [default: memcheck]
           Run the Valgrind tool called toolname, e.g. memcheck, cachegrind, callgrind, helgrind,
           drd, massif, dhat, lackey, none, exp-sgcheck, exp-bbv, etc.


       These options work with all tools.

       -h --help
           Show help for all options, both for the core and for the selected tool. If the option
           is repeated it is equivalent to giving --help-debug.

           Same as --help, but also lists debugging options which usually are only of use to
           Valgrind's developers.

           Show the version number of the Valgrind core. Tools can have their own version
           numbers. There is a scheme in place to ensure that tools only execute when the core
           version is one they are known to work with. This was done to minimise the chances of
           strange problems arising from tool-vs-core version incompatibilities.

       -q, --quiet
           Run silently, and only print error messages. Useful if you are running regression
           tests or have some other automated test machinery.

       -v, --verbose
           Be more verbose. Gives extra information on various aspects of your program, such as:
           the shared objects loaded, the suppressions used, the progress of the instrumentation
           and execution engines, and warnings about unusual behaviour. Repeating the option
           increases the verbosity level.

       --trace-children=<yes|no> [default: no]
           When enabled, Valgrind will trace into sub-processes initiated via the exec system
           call. This is necessary for multi-process programs.

           Note that Valgrind does trace into the child of a fork (it would be difficult not to,
           since fork makes an identical copy of a process), so this option is arguably badly
           named. However, most children of fork calls immediately call exec anyway.

           This option only has an effect when --trace-children=yes is specified. It allows for
           some children to be skipped. The option takes a comma separated list of patterns for
           the names of child executables that Valgrind should not trace into. Patterns may
           include the metacharacters ?  and *, which have the usual meaning.

           This can be useful for pruning uninteresting branches from a tree of processes being
           run on Valgrind. But you should be careful when using it. When Valgrind skips tracing
           into an executable, it doesn't just skip tracing that executable, it also skips
           tracing any of that executable's child processes. In other words, the flag doesn't
           merely cause tracing to stop at the specified executables -- it skips tracing of
           entire process subtrees rooted at any of the specified executables.

           This is the same as --trace-children-skip, with one difference: the decision as to
           whether to trace into a child process is made by examining the arguments to the child
           process, rather than the name of its executable.

       --child-silent-after-fork=<yes|no> [default: no]
           When enabled, Valgrind will not show any debugging or logging output for the child
           process resulting from a fork call. This can make the output less confusing (although
           more misleading) when dealing with processes that create children. It is particularly
           useful in conjunction with --trace-children=. Use of this option is also strongly
           recommended if you are requesting XML output (--xml=yes), since otherwise the XML from
           child and parent may become mixed up, which usually makes it useless.

       --vgdb=<no|yes|full> [default: yes]
           Valgrind will provide "gdbserver" functionality when --vgdb=yes or --vgdb=full is
           specified. This allows an external GNU GDB debugger to control and debug your program
           when it runs on Valgrind.  --vgdb=full incurs significant performance overheads, but
           provides more precise breakpoints and watchpoints. See Debugging your program using
           Valgrind's gdbserver and GDB for a detailed description.

           If the embedded gdbserver is enabled but no gdb is currently being used, the vgdb
           command line utility can send "monitor commands" to Valgrind from a shell. The
           Valgrind core provides a set of Valgrind monitor commands. A tool can optionally
           provide tool specific monitor commands, which are documented in the tool specific

       --vgdb-error=<number> [default: 999999999]
           Use this option when the Valgrind gdbserver is enabled with --vgdb=yes or --vgdb=full.
           Tools that report errors will wait for "number" errors to be reported before freezing
           the program and waiting for you to connect with GDB. It follows that a value of zero
           will cause the gdbserver to be started before your program is executed. This is
           typically used to insert GDB breakpoints before execution, and also works with tools
           that do not report errors, such as Massif.

       --vgdb-stop-at=<set> [default: none]
           Use this option when the Valgrind gdbserver is enabled with --vgdb=yes or --vgdb=full.
           The Valgrind gdbserver will be invoked for each error after --vgdb-error have been
           reported. You can additionally ask the Valgrind gdbserver to be invoked for other
           events, specified in one of the following ways:

           •   a comma separated list of one or more of startup exit valgrindabexit.

               The values startup exit valgrindabexit respectively indicate to invoke gdbserver
               before your program is executed, after the last instruction of your program, on
               Valgrind abnormal exit (e.g. internal error, out of memory, ...).

               Note: startup and --vgdb-error=0 will both cause Valgrind gdbserver to be invoked
               before your program is executed. The --vgdb-error=0 will in addition cause your
               program to stop on all subsequent errors.

           •   all to specify the complete set. It is equivalent to

           •   none for the empty set.

       --track-fds=<yes|no> [default: no]
           When enabled, Valgrind will print out a list of open file descriptors on exit or on
           request, via the gdbserver monitor command open_fds. Along with each file
           descriptor is printed a stack backtrace of where the file was opened and any details
           relating to the file descriptor such as the file name or socket details.

       --time-stamp=<yes|no> [default: no]
           When enabled, each message is preceded with an indication of the elapsed wallclock
           time since startup, expressed as days, hours, minutes, seconds and milliseconds.

       --log-fd=<number> [default: 2, stderr]
           Specifies that Valgrind should send all of its messages to the specified file
           descriptor. The default, 2, is the standard error channel (stderr). Note that this may
           interfere with the client's own use of stderr, as Valgrind's output will be
           interleaved with any output that the client sends to stderr.

           Specifies that Valgrind should send all of its messages to the specified file. If the
           file name is empty, it causes an abort. There are three special format specifiers that
           can be used in the file name.

           %p is replaced with the current process ID. This is very useful for program that
           invoke multiple processes. WARNING: If you use --trace-children=yes and your program
           invokes multiple processes OR your program forks without calling exec afterwards, and
           you don't use this specifier (or the %q specifier below), the Valgrind output from all
           those processes will go into one file, possibly jumbled up, and possibly incomplete.
           Note: If the program forks and calls exec afterwards, Valgrind output of the child
           from the period between fork and exec will be lost. Fortunately this gap is really
           tiny for most programs; and modern programs use posix_spawn anyway.

           %n is replaced with a file sequence number unique for this process. This is useful for
           processes that produces several files from the same filename template.

           %q{FOO} is replaced with the contents of the environment variable FOO. If the {FOO}
           part is malformed, it causes an abort. This specifier is rarely needed, but very
           useful in certain circumstances (eg. when running MPI programs). The idea is that you
           specify a variable which will be set differently for each process in the job, for
           example BPROC_RANK or whatever is applicable in your MPI setup. If the named
           environment variable is not set, it causes an abort. Note that in some shells, the {
           and } characters may need to be escaped with a backslash.

           %% is replaced with %.

           If an % is followed by any other character, it causes an abort.

           If the file name specifies a relative file name, it is put in the program's initial
           working directory: this is the current directory when the program started its
           execution after the fork or after the exec. If it specifies an absolute file name (ie.
           starts with '/') then it is put there.

           Specifies that Valgrind should send all of its messages to the specified port at the
           specified IP address. The port may be omitted, in which case port 1500 is used. If a
           connection cannot be made to the specified socket, Valgrind falls back to writing
           output to the standard error (stderr). This option is intended to be used in
           conjunction with the valgrind-listener program. For further details, see the
           commentary in the manual.


       These options are used by all tools that can report errors, e.g. Memcheck, but not

       --xml=<yes|no> [default: no]
           When enabled, the important parts of the output (e.g. tool error messages) will be in
           XML format rather than plain text. Furthermore, the XML output will be sent to a
           different output channel than the plain text output. Therefore, you also must use one
           of --xml-fd, --xml-file or --xml-socket to specify where the XML is to be sent.

           Less important messages will still be printed in plain text, but because the XML
           output and plain text output are sent to different output channels (the destination of
           the plain text output is still controlled by --log-fd, --log-file and --log-socket)
           this should not cause problems.

           This option is aimed at making life easier for tools that consume Valgrind's output as
           input, such as GUI front ends. Currently this option works with Memcheck, Helgrind,
           DRD and SGcheck. The output format is specified in the file
           docs/internals/xml-output-protocol4.txt in the source tree for Valgrind 3.5.0 or

           The recommended options for a GUI to pass, when requesting XML output, are: --xml=yes
           to enable XML output, --xml-file to send the XML output to a (presumably GUI-selected)
           file, --log-file to send the plain text output to a second GUI-selected file,
           --child-silent-after-fork=yes, and -q to restrict the plain text output to critical
           error messages created by Valgrind itself. For example, failure to read a specified
           suppressions file counts as a critical error message. In this way, for a successful
           run the text output file will be empty. But if it isn't empty, then it will contain
           important information which the GUI user should be made aware of.

       --xml-fd=<number> [default: -1, disabled]
           Specifies that Valgrind should send its XML output to the specified file descriptor.
           It must be used in conjunction with --xml=yes.

           Specifies that Valgrind should send its XML output to the specified file. It must be
           used in conjunction with --xml=yes. Any %p or %q sequences appearing in the filename
           are expanded in exactly the same way as they are for --log-file. See the description
           of --log-file for details.

           Specifies that Valgrind should send its XML output the specified port at the specified
           IP address. It must be used in conjunction with --xml=yes. The form of the argument is
           the same as that used by --log-socket. See the description of --log-socket for further

           Embeds an extra user comment string at the start of the XML output. Only works when
           --xml=yes is specified; ignored otherwise.

       --demangle=<yes|no> [default: yes]
           Enable/disable automatic demangling (decoding) of C++ names. Enabled by default. When
           enabled, Valgrind will attempt to translate encoded C++ names back to something
           approaching the original. The demangler handles symbols mangled by g++ versions 2.X,
           3.X and 4.X.

           An important fact about demangling is that function names mentioned in suppressions
           files should be in their mangled form. Valgrind does not demangle function names when
           searching for applicable suppressions, because to do otherwise would make suppression
           file contents dependent on the state of Valgrind's demangling machinery, and also slow
           down suppression matching.

       --num-callers=<number> [default: 12]
           Specifies the maximum number of entries shown in stack traces that identify program
           locations. Note that errors are commoned up using only the top four function locations
           (the place in the current function, and that of its three immediate callers). So this
           doesn't affect the total number of errors reported.

           The maximum value for this is 500. Note that higher settings will make Valgrind run a
           bit more slowly and take a bit more memory, but can be useful when working with
           programs with deeply-nested call chains.

       --unw-stack-scan-thresh=<number> [default: 0] , --unw-stack-scan-frames=<number> [default:
           Stack-scanning support is available only on ARM targets.

           These flags enable and control stack unwinding by stack scanning. When the normal
           stack unwinding mechanisms -- usage of Dwarf CFI records, and frame-pointer following
           -- fail, stack scanning may be able to recover a stack trace.

           Note that stack scanning is an imprecise, heuristic mechanism that may give very
           misleading results, or none at all. It should be used only in emergencies, when normal
           unwinding fails, and it is important to nevertheless have stack traces.

           Stack scanning is a simple technique: the unwinder reads words from the stack, and
           tries to guess which of them might be return addresses, by checking to see if they
           point just after ARM or Thumb call instructions. If so, the word is added to the

           The main danger occurs when a function call returns, leaving its return address
           exposed, and a new function is called, but the new function does not overwrite the old
           address. The result of this is that the backtrace may contain entries for functions
           which have already returned, and so be very confusing.

           A second limitation of this implementation is that it will scan only the page (4KB,
           normally) containing the starting stack pointer. If the stack frames are large, this
           may result in only a few (or not even any) being present in the trace. Also, if you
           are unlucky and have an initial stack pointer near the end of its containing page, the
           scan may miss all interesting frames.

           By default stack scanning is disabled. The normal use case is to ask for it when a
           stack trace would otherwise be very short. So, to enable it, use
           --unw-stack-scan-thresh=number. This requests Valgrind to try using stack scanning to
           "extend" stack traces which contain fewer than number frames.

           If stack scanning does take place, it will only generate at most the number of frames
           specified by --unw-stack-scan-frames. Typically, stack scanning generates so many
           garbage entries that this value is set to a low value (5) by default. In no case will
           a stack trace larger than the value specified by --num-callers be created.

       --error-limit=<yes|no> [default: yes]
           When enabled, Valgrind stops reporting errors after 10,000,000 in total, or 1,000
           different ones, have been seen. This is to stop the error tracking machinery from
           becoming a huge performance overhead in programs with many errors.

       --error-exitcode=<number> [default: 0]
           Specifies an alternative exit code to return if Valgrind reported any errors in the
           run. When set to the default value (zero), the return value from Valgrind will always
           be the return value of the process being simulated. When set to a nonzero value, that
           value is returned instead, if Valgrind detects any errors. This is useful for using
           Valgrind as part of an automated test suite, since it makes it easy to detect test
           cases for which Valgrind has reported errors, just by inspecting return codes.

       --exit-on-first-error=<yes|no> [default: no]
           If this option is enabled, Valgrind exits on the first error. A nonzero exit value
           must be defined using --error-exitcode option. Useful if you are running regression
           tests or have some other automated test machinery.

       --error-markers=<begin>,<end> [default: none]
           When errors are output as plain text (i.e. XML not used), --error-markers instructs to
           output a line containing the begin (end) string before (after) each error.

           Such marker lines facilitate searching for errors and/or extracting errors in an
           output file that contain valgrind errors mixed with the program output.

           Note that empty markers are accepted. So, only using a begin (or an end) marker is

       --show-error-list=no|yes [default: no]
           If this option is enabled, for tools that report errors, valgrind will show the list
           of detected errors and the list of used suppressions at exit.

           Note that at verbosity 2 and above, valgrind automatically shows the list of detected
           errors and the list of used suppressions at exit, unless --show-error-list=no is

           Specifying -s is equivalent to --show-error-list=yes.

       --sigill-diagnostics=<yes|no> [default: yes]
           Enable/disable printing of illegal instruction diagnostics. Enabled by default, but
           defaults to disabled when --quiet is given. The default can always be explicitly
           overridden by giving this option.

           When enabled, a warning message will be printed, along with some diagnostics, whenever
           an instruction is encountered that Valgrind cannot decode or translate, before the
           program is given a SIGILL signal. Often an illegal instruction indicates a bug in the
           program or missing support for the particular instruction in Valgrind. But some
           programs do deliberately try to execute an instruction that might be missing and trap
           the SIGILL signal to detect processor features. Using this flag makes it possible to
           avoid the diagnostic output that you would otherwise get in such cases.

       --keep-debuginfo=<yes|no> [default: no]
           When enabled, keep ("archive") symbols and all other debuginfo for unloaded code. This
           allows saved stack traces to include file/line info for code that has been dlclose'd
           (or similar). Be careful with this, since it can lead to unbounded memory use for
           programs which repeatedly load and unload shared objects.

           Some tools and some functionalities have only limited support for archived debug info.
           Memcheck fully supports it. Generally, tools that report errors can use archived debug
           info to show the error stack traces. The known limitations are: Helgrind's past access
           stack trace of a race condition is does not use archived debug info. Massif (and more
           generally the xtree Massif output format) does not make use of archived debug info.
           Only Memcheck has been (somewhat) tested with --keep-debuginfo=yes, so other tools may
           have unknown limitations.

       --show-below-main=<yes|no> [default: no]
           By default, stack traces for errors do not show any functions that appear beneath main
           because most of the time it's uninteresting C library stuff and/or gobbledygook.
           Alternatively, if main is not present in the stack trace, stack traces will not show
           any functions below main-like functions such as glibc's __libc_start_main.
           Furthermore, if main-like functions are present in the trace, they are normalised as
           (below main), in order to make the output more deterministic.

           If this option is enabled, all stack trace entries will be shown and main-like
           functions will not be normalised.

       --fullpath-after=<string> [default: don't show source paths]
           By default Valgrind only shows the filenames in stack traces, but not full paths to
           source files. When using Valgrind in large projects where the sources reside in
           multiple different directories, this can be inconvenient.  --fullpath-after provides a
           flexible solution to this problem. When this option is present, the path to each
           source file is shown, with the following all-important caveat: if string is found in
           the path, then the path up to and including string is omitted, else the path is shown
           unmodified. Note that string is not required to be a prefix of the path.

           For example, consider a file named /home/janedoe/blah/src/foo/bar/xyzzy.c. Specifying
           --fullpath-after=/home/janedoe/blah/src/ will cause Valgrind to show the name as

           Because the string is not required to be a prefix, --fullpath-after=src/ will produce
           the same output. This is useful when the path contains arbitrary machine-generated
           characters. For example, the path /my/build/dir/C32A1B47/blah/src/foo/xyzzy can be
           pruned to foo/xyzzy using --fullpath-after=/blah/src/.

           If you simply want to see the full path, just specify an empty string:
           --fullpath-after=. This isn't a special case, merely a logical consequence of the
           above rules.

           Finally, you can use --fullpath-after multiple times. Any appearance of it causes
           Valgrind to switch to producing full paths and applying the above filtering rule. Each
           produced path is compared against all the --fullpath-after-specified strings, in the
           order specified. The first string to match causes the path to be truncated as
           described above. If none match, the full path is shown. This facilitates chopping off
           prefixes when the sources are drawn from a number of unrelated directories.

       --extra-debuginfo-path=<path> [default: undefined and unused]
           By default Valgrind searches in several well-known paths for debug objects, such as

           However, there may be scenarios where you may wish to put debug objects at an
           arbitrary location, such as external storage when running Valgrind on a mobile device
           with limited local storage. Another example might be a situation where you do not have
           permission to install debug object packages on the system where you are running

           In these scenarios, you may provide an absolute path as an extra, final place for
           Valgrind to search for debug objects by specifying
           --extra-debuginfo-path=/path/to/debug/objects. The given path will be prepended to the
           absolute path name of the searched-for object. For example, if Valgrind is looking for
           the debuginfo for /w/x/y/ and --extra-debuginfo-path=/a/b/c is specified, it will
           look for a debug object at /a/b/c/w/x/y/

           This flag should only be specified once. If it is specified multiple times, only the
           last instance is honoured.

       --debuginfo-server=ipaddr:port [default: undefined and unused]
           This is a new, experimental, feature introduced in version 3.9.0.

           In some scenarios it may be convenient to read debuginfo from objects stored on a
           different machine. With this flag, Valgrind will query a debuginfo server running on
           ipaddr and listening on port port, if it cannot find the debuginfo object in the local

           The debuginfo server must accept TCP connections on port port. The debuginfo server is
           contained in the source file auxprogs/valgrind-di-server.c. It will only serve from
           the directory it is started in.  port defaults to 1500 in both client and server if
           not specified.

           If Valgrind looks for the debuginfo for /w/x/y/ by using the debuginfo server, it
           will strip the pathname components and merely request on the server. That in
           turn will look only in its current working directory for a matching debuginfo object.

           The debuginfo data is transmitted in small fragments (8 KB) as requested by Valgrind.
           Each block is compressed using LZO to reduce transmission time. The implementation has
           been tuned for best performance over a single-stage 802.11g (WiFi) network link.

           Note that checks for matching primary vs debug objects, using GNU debuglink CRC
           scheme, are performed even when using the debuginfo server. To disable such checking,
           you need to also specify --allow-mismatched-debuginfo=yes.

           By default the Valgrind build system will build valgrind-di-server for the target
           platform, which is almost certainly not what you want. So far we have been unable to
           find out how to get automake/autoconf to build it for the build platform. If you want
           to use it, you will have to recompile it by hand using the command shown at the top of

       --allow-mismatched-debuginfo=no|yes [no]
           When reading debuginfo from separate debuginfo objects, Valgrind will by default check
           that the main and debuginfo objects match, using the GNU debuglink mechanism. This
           guarantees that it does not read debuginfo from out of date debuginfo objects, and
           also ensures that Valgrind can't crash as a result of mismatches.

           This check can be overridden using --allow-mismatched-debuginfo=yes. This may be
           useful when the debuginfo and main objects have not been split in the proper way. Be
           careful when using this, though: it disables all consistency checking, and Valgrind
           has been observed to crash when the main and debuginfo objects don't match.

       --suppressions=<filename> [default: $PREFIX/lib/valgrind/default.supp]
           Specifies an extra file from which to read descriptions of errors to suppress. You may
           use up to 100 extra suppression files.

       --gen-suppressions=<yes|no|all> [default: no]
           When set to yes, Valgrind will pause after every error shown and print the line:

                   ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----

           Pressing Ret, or N Ret or n Ret, causes Valgrind continue execution without printing a
           suppression for this error.

           Pressing Y Ret or y Ret causes Valgrind to write a suppression for this error. You can
           then cut and paste it into a suppression file if you don't want to hear about the
           error in the future.

           When set to all, Valgrind will print a suppression for every reported error, without
           querying the user.

           This option is particularly useful with C++ programs, as it prints out the
           suppressions with mangled names, as required.

           Note that the suppressions printed are as specific as possible. You may want to common
           up similar ones, by adding wildcards to function names, and by using frame-level
           wildcards. The wildcarding facilities are powerful yet flexible, and with a bit of
           careful editing, you may be able to suppress a whole family of related errors with
           only a few suppressions.

           Sometimes two different errors are suppressed by the same suppression, in which case
           Valgrind will output the suppression more than once, but you only need to have one
           copy in your suppression file (but having more than one won't cause problems). Also,
           the suppression name is given as <insert a suppression name here>; the name doesn't
           really matter, it's only used with the -v option which prints out all used suppression

       --input-fd=<number> [default: 0, stdin]
           When using --gen-suppressions=yes, Valgrind will stop so as to read keyboard input
           from you when each error occurs. By default it reads from the standard input (stdin),
           which is problematic for programs which close stdin. This option allows you to specify
           an alternative file descriptor from which to read input.

       --dsymutil=no|yes [yes]
           This option is only relevant when running Valgrind on Mac OS X.

           Mac OS X uses a deferred debug information (debuginfo) linking scheme. When object
           files containing debuginfo are linked into a .dylib or an executable, the debuginfo is
           not copied into the final file. Instead, the debuginfo must be linked manually by
           running dsymutil, a system-provided utility, on the executable or .dylib. The
           resulting combined debuginfo is placed in a directory alongside the executable or
           .dylib, but with the extension .dSYM.

           With --dsymutil=no, Valgrind will detect cases where the .dSYM directory is either
           missing, or is present but does not appear to match the associated executable or
           .dylib, most likely because it is out of date. In these cases, Valgrind will print a
           warning message but take no further action.

           With --dsymutil=yes, Valgrind will, in such cases, automatically run dsymutil as
           necessary to bring the debuginfo up to date. For all practical purposes, if you always
           use --dsymutil=yes, then there is never any need to run dsymutil manually or as part
           of your applications's build system, since Valgrind will run it as necessary.

           Valgrind will not attempt to run dsymutil on any executable or library in /usr/,
           /bin/, /sbin/, /opt/, /sw/, /System/, /Library/ or /Applications/ since dsymutil will
           always fail in such situations. It fails both because the debuginfo for such
           pre-installed system components is not available anywhere, and also because it would
           require write privileges in those directories.

           Be careful when using --dsymutil=yes, since it will cause pre-existing .dSYM
           directories to be silently deleted and re-created. Also note that dsymutil is quite
           slow, sometimes excessively so.

       --max-stackframe=<number> [default: 2000000]
           The maximum size of a stack frame. If the stack pointer moves by more than this amount
           then Valgrind will assume that the program is switching to a different stack.

           You may need to use this option if your program has large stack-allocated arrays.
           Valgrind keeps track of your program's stack pointer. If it changes by more than the
           threshold amount, Valgrind assumes your program is switching to a different stack, and
           Memcheck behaves differently than it would for a stack pointer change smaller than the
           threshold. Usually this heuristic works well. However, if your program allocates large
           structures on the stack, this heuristic will be fooled, and Memcheck will subsequently
           report large numbers of invalid stack accesses. This option allows you to change the
           threshold to a different value.

           You should only consider use of this option if Valgrind's debug output directs you to
           do so. In that case it will tell you the new threshold you should specify.

           In general, allocating large structures on the stack is a bad idea, because you can
           easily run out of stack space, especially on systems with limited memory or which
           expect to support large numbers of threads each with a small stack, and also because
           the error checking performed by Memcheck is more effective for heap-allocated data
           than for stack-allocated data. If you have to use this option, you may wish to
           consider rewriting your code to allocate on the heap rather than on the stack.

       --main-stacksize=<number> [default: use current 'ulimit' value]
           Specifies the size of the main thread's stack.

           To simplify its memory management, Valgrind reserves all required space for the main
           thread's stack at startup. That means it needs to know the required stack size at

           By default, Valgrind uses the current "ulimit" value for the stack size, or 16 MB,
           whichever is lower. In many cases this gives a stack size in the range 8 to 16 MB,
           which almost never overflows for most applications.

           If you need a larger total stack size, use --main-stacksize to specify it. Only set it
           as high as you need, since reserving far more space than you need (that is, hundreds
           of megabytes more than you need) constrains Valgrind's memory allocators and may
           reduce the total amount of memory that Valgrind can use. This is only really of
           significance on 32-bit machines.

           On Linux, you may request a stack of size up to 2GB. Valgrind will stop with a
           diagnostic message if the stack cannot be allocated.

           --main-stacksize only affects the stack size for the program's initial thread. It has
           no bearing on the size of thread stacks, as Valgrind does not allocate those.

           You may need to use both --main-stacksize and --max-stackframe together. It is
           important to understand that --main-stacksize sets the maximum total stack size,
           whilst --max-stackframe specifies the largest size of any one stack frame. You will
           have to work out the --main-stacksize value for yourself (usually, if your
           applications segfaults). But Valgrind will tell you the needed --max-stackframe size,
           if necessary.

           As discussed further in the description of --max-stackframe, a requirement for a large
           stack is a sign of potential portability problems. You are best advised to place all
           large data in heap-allocated memory.

       --max-threads=<number> [default: 500]
           By default, Valgrind can handle to up to 500 threads. Occasionally, that number is too
           small. Use this option to provide a different limit. E.g.  --max-threads=3000.


       For tools that use their own version of malloc (e.g. Memcheck, Massif, Helgrind, DRD), the
       following options apply.

       --alignment=<number> [default: 8 or 16, depending on the platform]
           By default Valgrind's malloc, realloc, etc, return a block whose starting address is
           8-byte aligned or 16-byte aligned (the value depends on the platform and matches the
           platform default). This option allows you to specify a different alignment. The
           supplied value must be greater than or equal to the default, less than or equal to
           4096, and must be a power of two.

       --redzone-size=<number> [default: depends on the tool]
           Valgrind's malloc, realloc, etc, add padding blocks before and after each heap block
           allocated by the program being run. Such padding blocks are called redzones. The
           default value for the redzone size depends on the tool. For example, Memcheck adds and
           protects a minimum of 16 bytes before and after each block allocated by the client.
           This allows it to detect block underruns or overruns of up to 16 bytes.

           Increasing the redzone size makes it possible to detect overruns of larger distances,
           but increases the amount of memory used by Valgrind. Decreasing the redzone size will
           reduce the memory needed by Valgrind but also reduces the chances of detecting
           over/underruns, so is not recommended.

       --xtree-memory=none|allocs|full [none]
           Tools replacing Valgrind's malloc, realloc, etc, can optionally produce an execution
           tree detailing which piece of code is responsible for heap memory usage. See ???  for
           a detailed explanation about execution trees.

           When set to none, no memory execution tree is produced.

           When set to allocs, the memory execution tree gives the current number of allocated
           bytes and the current number of allocated blocks.

           When set to full, the memory execution tree gives 6 different measurements : the
           current number of allocated bytes and blocks (same values as for allocs), the total
           number of allocated bytes and blocks, the total number of freed bytes and blocks.

           Note that the overhead in cpu and memory to produce an xtree depends on the tool. The
           overhead in cpu is small for the value allocs, as the information needed to produce
           this report is maintained in any case by the tool. For massif and helgrind, specifying
           full implies to capture a stack trace for each free operation, while normally these
           tools only capture an allocation stack trace. For Memcheck, the cpu overhead for the
           value full is small, as this can only be used in combination with
           --keep-stacktraces=alloc-and-free or --keep-stacktraces=alloc-then-free, which already
           records a stack trace for each free operation. The memory overhead varies between 5
           and 10 words per unique stacktrace in the xtree, plus the memory needed to record the
           stack trace for the free operations, if needed specifically for the xtree.

       --xtree-memory-file=<filename> [default: xtmemory.kcg.%p]
           Specifies that Valgrind should produce the xtree memory report in the specified file.
           Any %p or %q sequences appearing in the filename are expanded in exactly the same way
           as they are for --log-file. See the description of --log-file for details.

           If the filename contains the extension .ms, then the produced file format will be a
           massif output file format. If the filename contains the extension .kcg or no extension
           is provided or recognised, then the produced file format will be a callgrind output

           See ???  for a detailed explanation about execution trees formats.


       These options apply to all tools, as they affect certain obscure workings of the Valgrind
       core. Most people won't need to use them.

       --smc-check=<none|stack|all|all-non-file> [default: all-non-file for x86/amd64/s390x,
       stack for other archs]
           This option controls Valgrind's detection of self-modifying code. If no checking is
           done, when a program executes some code, then overwrites it with new code, and
           executes the new code, Valgrind will continue to execute the translations it made for
           the old code. This will likely lead to incorrect behaviour and/or crashes.

           For "modern" architectures -- anything that's not x86, amd64 or s390x -- the default
           is stack. This is because a correct program must take explicit action to reestablish
           D-I cache coherence following code modification. Valgrind observes and honours such
           actions, with the result that self-modifying code is transparently handled with zero
           extra cost.

           For x86, amd64 and s390x, the program is not required to notify the hardware of
           required D-I coherence syncing. Hence the default is all-non-file, which covers the
           normal case of generating code into an anonymous (non-file-backed) mmap'd area.

           The meanings of the four available settings are as follows. No detection (none),
           detect self-modifying code on the stack (which is used by GCC to implement nested
           functions) (stack), detect self-modifying code everywhere (all), and detect
           self-modifying code everywhere except in file-backed mappings (all-non-file).

           Running with all will slow Valgrind down noticeably. Running with none will rarely
           speed things up, since very little code gets dynamically generated in most programs.
           The VALGRIND_DISCARD_TRANSLATIONS client request is an alternative to --smc-check=all
           and --smc-check=all-non-file that requires more programmer effort but allows Valgrind
           to run your program faster, by telling it precisely when translations need to be

           --smc-check=all-non-file provides a cheaper but more limited version of
           --smc-check=all. It adds checks to any translations that do not originate from
           file-backed memory mappings. Typical applications that generate code, for example JITs
           in web browsers, generate code into anonymous mmaped areas, whereas the "fixed" code
           of the browser always lives in file-backed mappings.  --smc-check=all-non-file takes
           advantage of this observation, limiting the overhead of checking to code which is
           likely to be JIT generated.

       --read-inline-info=<yes|no> [default: see below]
           When enabled, Valgrind will read information about inlined function calls from DWARF3
           debug info. This slows Valgrind startup and makes it use more memory (typically for
           each inlined piece of code, 6 words and space for the function name), but it results
           in more descriptive stacktraces. Currently, this functionality is enabled by default
           only for Linux, Android and Solaris targets and only for the tools Memcheck, Massif,
           Helgrind and DRD. Here is an example of some stacktraces with --read-inline-info=no:

               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x80484EA: main (inlinfo.c:6)
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048550: fun_noninline (inlinfo.c:6)
               ==15380==    by 0x804850E: main (inlinfo.c:34)
               ==15380== Conditional jump or move depends on uninitialised value(s)
               ==15380==    at 0x8048520: main (inlinfo.c:6)

           And here are the same errors with --read-inline-info=yes:

               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x80484EA: fun_d (inlinfo.c:6)
               ==15377==    by 0x80484EA: fun_c (inlinfo.c:14)
               ==15377==    by 0x80484EA: fun_b (inlinfo.c:20)
               ==15377==    by 0x80484EA: fun_a (inlinfo.c:26)
               ==15377==    by 0x80484EA: main (inlinfo.c:33)
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048550: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048550: fun_noninline (inlinfo.c:41)
               ==15377==    by 0x804850E: main (inlinfo.c:34)
               ==15377== Conditional jump or move depends on uninitialised value(s)
               ==15377==    at 0x8048520: fun_d (inlinfo.c:6)
               ==15377==    by 0x8048520: main (inlinfo.c:35)

       --read-var-info=<yes|no> [default: no]
           When enabled, Valgrind will read information about variable types and locations from
           DWARF3 debug info. This slows Valgrind startup significantly and makes it use
           significantly more memory, but for the tools that can take advantage of it (Memcheck,
           Helgrind, DRD) it can result in more precise error messages. For example, here are
           some standard errors issued by Memcheck:

               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048544: main (varinfo1.c:55)
               ==15363==  Address 0x80497f7 is 7 bytes inside data symbol "global_i2"
               ==15363== Uninitialised byte(s) found during client check request
               ==15363==    at 0x80484A9: croak (varinfo1.c:28)
               ==15363==    by 0x8048550: main (varinfo1.c:56)
               ==15363==  Address 0xbea0d0cc is on thread 1's stack
               ==15363==  in frame #1, created by main (varinfo1.c:45)

           And here are the same errors with --read-var-info=yes:

               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048544: main (varinfo1.c:55)
               ==15370==  Location 0x80497f7 is 0 bytes inside global_i2[7],
               ==15370==  a global variable declared at varinfo1.c:41
               ==15370== Uninitialised byte(s) found during client check request
               ==15370==    at 0x80484A9: croak (varinfo1.c:28)
               ==15370==    by 0x8048550: main (varinfo1.c:56)
               ==15370==  Location 0xbeb4a0cc is 0 bytes inside local var "local"
               ==15370==  declared at varinfo1.c:46, in frame #1 of thread 1

       --vgdb-poll=<number> [default: 5000]
           As part of its main loop, the Valgrind scheduler will poll to check if some activity
           (such as an external command or some input from a gdb) has to be handled by gdbserver.
           This activity poll will be done after having run the given number of basic blocks (or
           slightly more than the given number of basic blocks). This poll is quite cheap so the
           default value is set relatively low. You might further decrease this value if vgdb
           cannot use ptrace system call to interrupt Valgrind if all threads are (most of the
           time) blocked in a system call.

       --vgdb-shadow-registers=no|yes [default: no]
           When activated, gdbserver will expose the Valgrind shadow registers to GDB. With this,
           the value of the Valgrind shadow registers can be examined or changed using GDB.
           Exposing shadow registers only works with GDB version 7.1 or later.

       --vgdb-prefix=<prefix> [default: /tmp/vgdb-pipe]
           To communicate with gdb/vgdb, the Valgrind gdbserver creates 3 files (2 named FIFOs
           and a mmap shared memory file). The prefix option controls the directory and prefix
           for the creation of these files.

       --run-libc-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux.

           The GNU C library (, which is used by all programs, may allocate memory for
           its own uses. Usually it doesn't bother to free that memory when the program ends—
           there would be no point, since the Linux kernel reclaims all process resources when a
           process exits anyway, so it would just slow things down.

           The glibc authors realised that this behaviour causes leak checkers, such as Valgrind,
           to falsely report leaks in glibc, when a leak check is done at exit. In order to avoid
           this, they provided a routine called __libc_freeres specifically to make glibc release
           all memory it has allocated. Memcheck therefore tries to run __libc_freeres at exit.

           Unfortunately, in some very old versions of glibc, __libc_freeres is sufficiently
           buggy to cause segmentation faults. This was particularly noticeable on Red Hat 7.1.
           So this option is provided in order to inhibit the run of __libc_freeres. If your
           program seems to run fine on Valgrind, but segfaults at exit, you may find that
           --run-libc-freeres=no fixes that, although at the cost of possibly falsely reporting
           space leaks in

       --run-cxx-freeres=<yes|no> [default: yes]
           This option is only relevant when running Valgrind on Linux or Solaris C++ programs.

           The GNU Standard C++ library (, which is used by all C++ programs
           compiled with g++, may allocate memory for its own uses. Usually it doesn't bother to
           free that memory when the program ends—there would be no point, since the kernel
           reclaims all process resources when a process exits anyway, so it would just slow
           things down.

           The gcc authors realised that this behaviour causes leak checkers, such as Valgrind,
           to falsely report leaks in libstdc++, when a leak check is done at exit. In order to
           avoid this, they provided a routine called __gnu_cxx::__freeres specifically to make
           libstdc++ release all memory it has allocated. Memcheck therefore tries to run
           __gnu_cxx::__freeres at exit.

           For the sake of flexibility and unforeseen problems with __gnu_cxx::__freeres, option
           --run-cxx-freeres=no exists, although at the cost of possibly falsely reporting space
           leaks in

           Pass miscellaneous hints to Valgrind which slightly modify the simulated behaviour in
           nonstandard or dangerous ways, possibly to help the simulation of strange features. By
           default no hints are enabled. Use with caution! Currently known hints are:

           •   lax-ioctls: Be very lax about ioctl handling; the only assumption is that the size
               is correct. Doesn't require the full buffer to be initialised when writing.
               Without this, using some device drivers with a large number of strange ioctl
               commands becomes very tiresome.

           •   fuse-compatible: Enable special handling for certain system calls that may block
               in a FUSE file-system. This may be necessary when running Valgrind on a
               multi-threaded program that uses one thread to manage a FUSE file-system and
               another thread to access that file-system.

           •   enable-outer: Enable some special magic needed when the program being run is
               itself Valgrind.

           •   no-inner-prefix: Disable printing a prefix > in front of each stdout or stderr
               output line in an inner Valgrind being run by an outer Valgrind. This is useful
               when running Valgrind regression tests in an outer/inner setup. Note that the
               prefix > will always be printed in front of the inner debug logging lines.

           •   no-nptl-pthread-stackcache: This hint is only relevant when running Valgrind on
               Linux; it is ignored on Solaris and Mac OS X.

               The GNU glibc pthread library (, which is used by pthread programs,
               maintains a cache of pthread stacks. When a pthread terminates, the memory used
               for the pthread stack and some thread local storage related data structure are not
               always directly released. This memory is kept in a cache (up to a certain size),
               and is re-used if a new thread is started.

               This cache causes the helgrind tool to report some false positive race condition
               errors on this cached memory, as helgrind does not understand the internal glibc
               cache synchronisation primitives. So, when using helgrind, disabling the cache
               helps to avoid false positive race conditions, in particular when using thread
               local storage variables (e.g. variables using the __thread qualifier).

               When using the memcheck tool, disabling the cache ensures the memory used by glibc
               to handle __thread variables is directly released when a thread terminates.

               Note: Valgrind disables the cache using some internal knowledge of the glibc stack
               cache implementation and by examining the debug information of the pthread
               library. This technique is thus somewhat fragile and might not work for all glibc
               versions. This has been successfully tested with various glibc versions (e.g.
               2.11, 2.16, 2.18) on various platforms.

           •   lax-doors: (Solaris only) Be very lax about door syscall handling over
               unrecognised door file descriptors. Does not require that full buffer is
               initialised when writing. Without this, programs using libdoor(3LIB) functionality
               with completely proprietary semantics may report large number of false positives.

           •   fallback-llsc: (MIPS and ARM64 only): Enables an alternative implementation of
               Load-Linked (LL) and Store-Conditional (SC) instructions. The standard
               implementation gives more correct behaviour, but can cause indefinite looping on
               certain processor implementations that are intolerant of extra memory references
               between LL and SC. So far this is known only to happen on Cavium 3 cores. You
               should not need to use this flag, since the relevant cores are detected at startup
               and the alternative implementation is automatically enabled if necessary. There is
               no equivalent anti-flag: you cannot force-disable the alternative implementation,
               if it is automatically enabled. The underlying problem exists because the
               "standard" implementation of LL and SC is done by copying through LL and SC
               instructions into the instrumented code. However, tools may insert extra
               instrumentation memory references in between the LL and SC instructions. These
               memory references are not present in the original uninstrumented code, and their
               presence in the instrumented code can cause the SC instructions to persistently
               fail, leading to indefinite looping in LL-SC blocks. The alternative
               implementation gives correct behaviour of LL and SC instructions between threads
               in a process, up to and including the ABA scenario. It also gives correct
               behaviour between a Valgrinded thread and a non-Valgrinded thread running in a
               different process, that communicate via shared memory, but only up to and
               including correct CAS behaviour -- in this case the ABA scenario may not be
               correctly handled.

       --fair-sched=<no|yes|try> [default: no]
           The --fair-sched option controls the locking mechanism used by Valgrind to serialise
           thread execution. The locking mechanism controls the way the threads are scheduled,
           and different settings give different trade-offs between fairness and performance. For
           more details about the Valgrind thread serialisation scheme and its impact on
           performance and thread scheduling, see Scheduling and Multi-Thread Performance.

           •   The value --fair-sched=yes activates a fair scheduler. In short, if multiple
               threads are ready to run, the threads will be scheduled in a round robin fashion.
               This mechanism is not available on all platforms or Linux versions. If not
               available, using --fair-sched=yes will cause Valgrind to terminate with an error.

               You may find this setting improves overall responsiveness if you are running an
               interactive multithreaded program, for example a web browser, on Valgrind.

           •   The value --fair-sched=try activates fair scheduling if available on the platform.
               Otherwise, it will automatically fall back to --fair-sched=no.

           •   The value --fair-sched=no activates a scheduler which does not guarantee fairness
               between threads ready to run, but which in general gives the highest performance.

           Handle system calls and ioctls arising from minor variants of the default kernel for
           this platform. This is useful for running on hacked kernels or with kernel modules
           which support nonstandard ioctls, for example. Use with caution. If you don't
           understand what this option does then you almost certainly don't need it. Currently
           known variants are:

           •   bproc: support the sys_broc system call on x86. This is for running on BProc,
               which is a minor variant of standard Linux which is sometimes used for building

           •   android-no-hw-tls: some versions of the Android emulator for ARM do not provide a
               hardware TLS (thread-local state) register, and Valgrind crashes at startup. Use
               this variant to select software support for TLS.

           •   android-gpu-sgx5xx: use this to support handling of proprietary ioctls for the
               PowerVR SGX 5XX series of GPUs on Android devices. Failure to select this does not
               cause stability problems, but may cause Memcheck to report false errors after the
               program performs GPU-specific ioctls.

           •   android-gpu-adreno3xx: similarly, use this to support handling of proprietary
               ioctls for the Qualcomm Adreno 3XX series of GPUs on Android devices.

       --merge-recursive-frames=<number> [default: 0]
           Some recursive algorithms, for example balanced binary tree implementations, create
           many different stack traces, each containing cycles of calls. A cycle is defined as
           two identical program counter values separated by zero or more other program counter
           values. Valgrind may then use a lot of memory to store all these stack traces. This is
           a poor use of memory considering that such stack traces contain repeated uninteresting
           recursive calls instead of more interesting information such as the function that has
           initiated the recursive call.

           The option --merge-recursive-frames=<number> instructs Valgrind to detect and merge
           recursive call cycles having a size of up to <number> frames. When such a cycle is
           detected, Valgrind records the cycle in the stack trace as a unique program counter.

           The value 0 (the default) causes no recursive call merging. A value of 1 will cause
           stack traces of simple recursive algorithms (for example, a factorial implementation)
           to be collapsed. A value of 2 will usually be needed to collapse stack traces produced
           by recursive algorithms such as binary trees, quick sort, etc. Higher values might be
           needed for more complex recursive algorithms.

           Note: recursive calls are detected by analysis of program counter values. They are not
           detected by looking at function names.

       --num-transtab-sectors=<number> [default: 6 for Android platforms, 16 for all others]
           Valgrind translates and instruments your program's machine code in small fragments
           (basic blocks). The translations are stored in a translation cache that is divided
           into a number of sections (sectors). If the cache is full, the sector containing the
           oldest translations is emptied and reused. If these old translations are needed again,
           Valgrind must re-translate and re-instrument the corresponding machine code, which is
           expensive. If the "executed instructions" working set of a program is big, increasing
           the number of sectors may improve performance by reducing the number of
           re-translations needed. Sectors are allocated on demand. Once allocated, a sector can
           never be freed, and occupies considerable space, depending on the tool and the value
           of --avg-transtab-entry-size (about 40 MB per sector for Memcheck). Use the option
           --stats=yes to obtain precise information about the memory used by a sector and the
           allocation and recycling of sectors.

       --avg-transtab-entry-size=<number> [default: 0, meaning use tool provided default]
           Average size of translated basic block. This average size is used to dimension the
           size of a sector. Each tool provides a default value to be used. If this default value
           is too small, the translation sectors will become full too quickly. If this default
           value is too big, a significant part of the translation sector memory will be unused.
           Note that the average size of a basic block translation depends on the tool, and might
           depend on tool options. For example, the memcheck option --track-origins=yes increases
           the size of the basic block translations. Use --avg-transtab-entry-size to tune the
           size of the sectors, either to gain memory or to avoid too many retranslations.

       --aspace-minaddr=<address> [default: depends on the platform]
           To avoid potential conflicts with some system libraries, Valgrind does not use the
           address space below --aspace-minaddr value, keeping it reserved in case a library
           specifically requests memory in this region. So, some "pessimistic" value is guessed
           by Valgrind depending on the platform. On linux, by default, Valgrind avoids using the
           first 64MB even if typically there is no conflict in this complete zone. You can use
           the option --aspace-minaddr to have your memory hungry application benefitting from
           more of this lower memory. On the other hand, if you encounter a conflict, increasing
           aspace-minaddr value might solve it. Conflicts will typically manifest themselves with
           mmap failures in the low range of the address space. The provided address must be page
           aligned and must be equal or bigger to 0x1000 (4KB). To find the default value on your
           platform, do something such as valgrind -d -d date 2>&1 | grep -i minaddr. Values
           lower than 0x10000 (64KB) are known to create problems on some distributions.

       --valgrind-stacksize=<number> [default: 1MB]
           For each thread, Valgrind needs its own 'private' stack. The default size for these
           stacks is largely dimensioned, and so should be sufficient in most cases. In case the
           size is too small, Valgrind will segfault. Before segfaulting, a warning might be
           produced by Valgrind when approaching the limit.

           Use the option --valgrind-stacksize if such an (unlikely) warning is produced, or
           Valgrind dies due to a segmentation violation. Such segmentation violations have been
           seen when demangling huge C++ symbols.

           If your application uses many threads and needs a lot of memory, you can gain some
           memory by reducing the size of these Valgrind stacks using the option

       --show-emwarns=<yes|no> [default: no]
           When enabled, Valgrind will emit warnings about its CPU emulation in certain cases.
           These are usually not interesting.

           When a shared object whose soname matches sonamepatt is loaded into the process,
           examine all the text symbols it exports. If none of those match fnnamepatt, print an
           error message and abandon the run. This makes it possible to ensure that the run does
           not continue unless a given shared object contains a particular function name.

           Both sonamepatt and fnnamepatt can be written using the usual ?  and * wildcards. For
           example: ":**:foo?bar". You may use characters other than a colon to separate
           the two patterns. It is only important that the first character and the separator
           character are the same. For example, the above example could also be written
           "Q**Qfoo?bar". Multiple
            --require-text-symbol flags are allowed, in which case shared objects that are loaded
           into the process will be checked against all of them.

           The purpose of this is to support reliable usage of marked-up libraries. For example,
           suppose we have a version of GCC's which has been marked up with
           annotations to support Helgrind. It is only too easy and confusing to load the wrong,
           un-annotated into the application. So the idea is: add a text symbol in the
           marked-up library, for example annotated_for_helgrind_3_6, and then give the flag
           --require-text-symbol=:*libgomp*so*:annotated_for_helgrind_3_6 so that when
           is loaded, Valgrind scans its symbol table, and if the symbol isn't present the run is
           aborted, rather than continuing silently with the un-marked-up library. Note that you
           should put the entire flag in quotes to stop shells expanding up the * and ?

           When a shared library is loaded, Valgrind checks for functions in the library that
           must be replaced or wrapped. For example, Memcheck replaces some string and memory
           functions (strchr, strlen, strcpy, memchr, memcpy, memmove, etc.) with its own
           versions. Such replacements are normally done only in shared libraries whose soname
           matches a predefined soname pattern (e.g.* on linux). By default, no
           replacement is done for a statically linked binary or for alternative libraries,
           except for the allocation functions (malloc, free, calloc, memalign, realloc, operator
           new, operator delete, etc.) Such allocation functions are intercepted by default in
           any shared library or in the executable if they are exported as global symbols. This
           means that if a replacement allocation library such as tcmalloc is found, its
           functions are also intercepted by default. In some cases, the replacements allow
           --soname-synonyms to specify one additional synonym pattern, giving flexibility in the
           replacement. Or to prevent interception of all public allocation symbols.

           Currently, this flexibility is only allowed for the malloc related functions, using
           the synonym somalloc. This synonym is usable for all tools doing standard replacement
           of malloc related functions (e.g. memcheck, helgrind, drd, massif, dhat, exp-sgcheck).

           •   Alternate malloc library: to replace the malloc related functions in a specific
               alternate library with soname (and not in any others), give the
               option A pattern can be used to match
               multiple libraries sonames. For example, --soname-synonyms=somalloc=*tcmalloc*
               will match the soname of all variants of the tcmalloc library (native, debug,
               profiled, ... tcmalloc variants).

               Note: the soname of a elf shared library can be retrieved using the readelf

           •   Replacements in a statically linked library are done by using the NONE pattern.
               For example, if you link with libtcmalloc.a, and only want to intercept the malloc
               related functions in the executable (and standard libraries) themselves, but not
               any other shared libraries, you can give the option
               --soname-synonyms=somalloc=NONE. Note that a NONE pattern will match the main
               executable and any shared library having no soname.

           •   To run a "default" Firefox build for Linux, in which JEMalloc is linked in to the
               main executable, use --soname-synonyms=somalloc=NONE.

           •   To only intercept allocation symbols in the default system libraries, but not in
               any other shared library or the executable defining public malloc or operator new
               related functions use a non-existing library name like
               --soname-synonyms=somalloc=nouserintercepts (where nouserintercepts can be any
               non-existing library name).

           •   Shared library of the dynamic (runtime) linker is excluded from searching for
               global public symbols, such as those for the malloc related functions (identified
               by somalloc synonym).

       --progress-interval=<number> [default: 0, meaning 'disabled']
           This is an enhancement to Valgrind's debugging output. It is unlikely to be of
           interest to end users.

           When number is set to a non-zero value, Valgrind will print a one-line progress
           summary every number seconds. Valid settings for number are between 0 and 3600
           inclusive. Here's some example output with number set to 10:

               PROGRESS: U 110s, W 113s, 97.3% CPU, EvC 414.79M, TIn 616.7k, TOut 0.5k, #thr 67
               PROGRESS: U 120s, W 124s, 96.8% CPU, EvC 505.27M, TIn 636.6k, TOut 3.0k, #thr 64
               PROGRESS: U 130s, W 134s, 97.0% CPU, EvC 574.90M, TIn 657.5k, TOut 3.0k, #thr 63

           Each line shows:

           •   U: total user time.RE

               •   W: total wallclock time.RE

                   •   CPU: overall average cpu use.RE

                       •   EvC: number of event checks.  An event
                                    check is a backwards branch in the simulated program, so this
                           is a
                                    measure of forward progress of the program.RE

                           •   TIn: number of code blocks instrumented
                                         by the JIT.RE

                               •   TOut: number of instrumented code
                                             blocks that have been thrown away.RE

                                   •   #thr: number of threads in the

                                       From the progress of these, it is possible to observe:

                                       •   when the program is compute bound (TIn
                                                     rises slowly, EvC rises rapidly).RE

                                           •   when the program is in a spinloop
                                                         fixed, EvC rises rapidly).RE

                                               •   when the program is JIT-bound (TIn
                                                             rises rapidly).RE

                                                   •   when the program is rapidly discarding
                                                                 (TOut rises rapidly).RE

                                                       •   when the program is about to achieve
                                                           some expected state
                                                                     (EvC arrives at some value

                                                           •    when the program is idling (U
                                                                         more slowly than W).RE


       There are also some options for debugging Valgrind itself. You shouldn't need to use them
       in the normal run of things. If you wish to see the list, use the --help-debug option.


       --leak-check=<no|summary|yes|full> [default: summary]
           When enabled, search for memory leaks when the client program finishes. If set to
           summary, it says how many leaks occurred. If set to full or yes, each individual leak
           will be shown in detail and/or counted as an error, as specified by the options
           --show-leak-kinds and --errors-for-leak-kinds.

       --leak-resolution=<low|med|high> [default: high]
           When doing leak checking, determines how willing Memcheck is to consider different
           backtraces to be the same for the purposes of merging multiple leaks into a single
           leak report. When set to low, only the first two entries need match. When med, four
           entries have to match. When high, all entries need to match.

           For hardcore leak debugging, you probably want to use --leak-resolution=high together
           with --num-callers=40 or some such large number.

           Note that the --leak-resolution setting does not affect Memcheck's ability to find
           leaks. It only changes how the results are presented.

       --show-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to show in a full leak search, in one of the following ways:

           •   a comma separated list of one or more of definite indirect possible reachable.

           •   all to specify the complete set (all leak kinds). It is equivalent to

           •   none for the empty set.

       --errors-for-leak-kinds=<set> [default: definite,possible]
           Specifies the leak kinds to count as errors in a full leak search. The <set> is
           specified similarly to --show-leak-kinds

       --leak-check-heuristics=<set> [default: all]
           Specifies the set of leak check heuristics to be used during leak searches. The
           heuristics control which interior pointers to a block cause it to be considered as
           reachable. The heuristic set is specified in one of the following ways:

           •   a comma separated list of one or more of stdstring length64 newarray

           •   all to activate the complete set of heuristics. It is equivalent to

           •   none for the empty set.

           Note that these heuristics are dependent on the layout of the objects produced by the
           C++ compiler. They have been tested with some gcc versions (e.g. 4.4 and 4.7). They
           might not work properly with other C++ compilers.

       --show-reachable=<yes|no> , --show-possibly-lost=<yes|no>
           These options provide an alternative way to specify the leak kinds to show:

           •   --show-reachable=no --show-possibly-lost=yes is equivalent to

           •   --show-reachable=no --show-possibly-lost=no is equivalent to

           •   --show-reachable=yes is equivalent to --show-leak-kinds=all.

           Note that --show-possibly-lost=no has no effect if --show-reachable=yes is specified.

       --xtree-leak=<no|yes> [no]
           If set to yes, the results for the leak search done at exit will be output in a
           'Callgrind Format' execution tree file. Note that this automatically sets the options
           --leak-check=full and --show-leak-kinds=all, to allow xtree visualisation tools such
           as kcachegrind to select what kind to leak to visualise. The produced file will
           contain the following events:

           •   RB : Reachable Bytes

           •   PB : Possibly lost Bytes

           •   IB : Indirectly lost Bytes

           •   DB : Definitely lost Bytes (direct plus indirect)

           •   DIB : Definitely Indirectly lost Bytes (subset of DB)

           •   RBk : reachable Blocks

           •   PBk : Possibly lost Blocks

           •   IBk : Indirectly lost Blocks

           •   DBk : Definitely lost Blocks

           The increase or decrease for all events above will also be output in the file to
           provide the delta (increase or decrease) between 2 successive leak searches. For
           example, iRB is the increase of the RB event, dPBk is the decrease of PBk event. The
           values for the increase and decrease events will be zero for the first leak search

           See ???  for a detailed explanation about execution trees.

       --xtree-leak-file=<filename> [default: xtleak.kcg.%p]
           Specifies that Valgrind should produce the xtree leak report in the specified file.
           Any %p, %q or %n sequences appearing in the filename are expanded in exactly the same
           way as they are for --log-file. See the description of --log-file for details.

           See ???  for a detailed explanation about execution trees formats.

       --undef-value-errors=<yes|no> [default: yes]
           Controls whether Memcheck reports uses of undefined value errors. Set this to no if
           you don't want to see undefined value errors. It also has the side effect of speeding
           up Memcheck somewhat. AddrCheck (removed in Valgrind 3.1.0) functioned like Memcheck
           with --undef-value-errors=no.

       --track-origins=<yes|no> [default: no]
           Controls whether Memcheck tracks the origin of uninitialised values. By default, it
           does not, which means that although it can tell you that an uninitialised value is
           being used in a dangerous way, it cannot tell you where the uninitialised value came
           from. This often makes it difficult to track down the root problem.

           When set to yes, Memcheck keeps track of the origins of all uninitialised values.
           Then, when an uninitialised value error is reported, Memcheck will try to show the
           origin of the value. An origin can be one of the following four places: a heap block,
           a stack allocation, a client request, or miscellaneous other sources (eg, a call to

           For uninitialised values originating from a heap block, Memcheck shows where the block
           was allocated. For uninitialised values originating from a stack allocation, Memcheck
           can tell you which function allocated the value, but no more than that -- typically it
           shows you the source location of the opening brace of the function. So you should
           carefully check that all of the function's local variables are initialised properly.

           Performance overhead: origin tracking is expensive. It halves Memcheck's speed and
           increases memory use by a minimum of 100MB, and possibly more. Nevertheless it can
           drastically reduce the effort required to identify the root cause of uninitialised
           value errors, and so is often a programmer productivity win, despite running more

           Accuracy: Memcheck tracks origins quite accurately. To avoid very large space and time
           overheads, some approximations are made. It is possible, although unlikely, that
           Memcheck will report an incorrect origin, or not be able to identify any origin.

           Note that the combination --track-origins=yes and --undef-value-errors=no is
           nonsensical. Memcheck checks for and rejects this combination at startup.

       --partial-loads-ok=<yes|no> [default: yes]
           Controls how Memcheck handles 32-, 64-, 128- and 256-bit naturally aligned loads from
           addresses for which some bytes are addressable and others are not. When yes, such
           loads do not produce an address error. Instead, loaded bytes originating from illegal
           addresses are marked as uninitialised, and those corresponding to legal addresses are
           handled in the normal way.

           When no, loads from partially invalid addresses are treated the same as loads from
           completely invalid addresses: an illegal-address error is issued, and the resulting
           bytes are marked as initialised.

           Note that code that behaves in this way is in violation of the ISO C/C++ standards,
           and should be considered broken. If at all possible, such code should be fixed.

       --expensive-definedness-checks=<no|auto|yes> [default: auto]
           Controls whether Memcheck should employ more precise but also more expensive (time
           consuming) instrumentation when checking the definedness of certain values. In
           particular, this affects the instrumentation of integer adds, subtracts and equality

           Selecting --expensive-definedness-checks=yes causes Memcheck to use the most accurate
           analysis possible. This minimises false error rates but can cause up to 30%
           performance degradation.

           Selecting --expensive-definedness-checks=no causes Memcheck to use the cheapest
           instrumentation possible. This maximises performance but will normally give an
           unusably high false error rate.

           The default setting, --expensive-definedness-checks=auto, is strongly recommended.
           This causes Memcheck to use the minimum of expensive instrumentation needed to achieve
           the same false error rate as --expensive-definedness-checks=yes. It also enables an
           instrumentation-time analysis pass which aims to further reduce the costs of accurate
           instrumentation. Overall, the performance loss is generally around 5% relative to
           --expensive-definedness-checks=no, although this is strongly workload dependent. Note
           that the exact instrumentation settings in this mode are architecture dependent.

       --keep-stacktraces=alloc|free|alloc-and-free|alloc-then-free|none [default:
           Controls which stack trace(s) to keep for malloc'd and/or free'd blocks.

           With alloc-then-free, a stack trace is recorded at allocation time, and is associated
           with the block. When the block is freed, a second stack trace is recorded, and this
           replaces the allocation stack trace. As a result, any "use after free" errors relating
           to this block can only show a stack trace for where the block was freed.

           With alloc-and-free, both allocation and the deallocation stack traces for the block
           are stored. Hence a "use after free" error will show both, which may make the error
           easier to diagnose. Compared to alloc-then-free, this setting slightly increases
           Valgrind's memory use as the block contains two references instead of one.

           With alloc, only the allocation stack trace is recorded (and reported). With free,
           only the deallocation stack trace is recorded (and reported). These values somewhat
           decrease Valgrind's memory and cpu usage. They can be useful depending on the error
           types you are searching for and the level of detail you need to analyse them. For
           example, if you are only interested in memory leak errors, it is sufficient to record
           the allocation stack traces.

           With none, no stack traces are recorded for malloc and free operations. If your
           program allocates a lot of blocks and/or allocates/frees from many different stack
           traces, this can significantly decrease cpu and/or memory required. Of course, few
           details will be reported for errors related to heap blocks.

           Note that once a stack trace is recorded, Valgrind keeps the stack trace in memory
           even if it is not referenced by any block. Some programs (for example, recursive
           algorithms) can generate a huge number of stack traces. If Valgrind uses too much
           memory in such circumstances, you can reduce the memory required with the options
           --keep-stacktraces and/or by using a smaller value for the option --num-callers.

           If you want to use --xtree-memory=full memory profiling (see ???  ), then you cannot
           specify --keep-stacktraces=free or --keep-stacktraces=none.

       --freelist-vol=<number> [default: 20000000]
           When the client program releases memory using free (in C) or delete (C++), that memory
           is not immediately made available for re-allocation. Instead, it is marked
           inaccessible and placed in a queue of freed blocks. The purpose is to defer as long as
           possible the point at which freed-up memory comes back into circulation. This
           increases the chance that Memcheck will be able to detect invalid accesses to blocks
           for some significant period of time after they have been freed.

           This option specifies the maximum total size, in bytes, of the blocks in the queue.
           The default value is twenty million bytes. Increasing this increases the total amount
           of memory used by Memcheck but may detect invalid uses of freed blocks which would
           otherwise go undetected.

       --freelist-big-blocks=<number> [default: 1000000]
           When making blocks from the queue of freed blocks available for re-allocation,
           Memcheck will in priority re-circulate the blocks with a size greater or equal to
           --freelist-big-blocks. This ensures that freeing big blocks (in particular freeing
           blocks bigger than --freelist-vol) does not immediately lead to a re-circulation of
           all (or a lot of) the small blocks in the free list. In other words, this option
           increases the likelihood to discover dangling pointers for the "small" blocks, even
           when big blocks are freed.

           Setting a value of 0 means that all the blocks are re-circulated in a FIFO order.

       --workaround-gcc296-bugs=<yes|no> [default: no]
           When enabled, assume that reads and writes some small distance below the stack pointer
           are due to bugs in GCC 2.96, and does not report them. The "small distance" is 256
           bytes by default. Note that GCC 2.96 is the default compiler on some ancient Linux
           distributions (RedHat 7.X) and so you may need to use this option. Do not use it if
           you do not have to, as it can cause real errors to be overlooked. A better alternative
           is to use a more recent GCC in which this bug is fixed.

           You may also need to use this option when working with GCC 3.X or 4.X on 32-bit
           PowerPC Linux. This is because GCC generates code which occasionally accesses below
           the stack pointer, particularly for floating-point to/from integer conversions. This
           is in violation of the 32-bit PowerPC ELF specification, which makes no provision for
           locations below the stack pointer to be accessible.

           This option is deprecated as of version 3.12 and may be removed from future versions.
           You should instead use --ignore-range-below-sp to specify the exact range of offsets
           below the stack pointer that should be ignored. A suitable equivalent is

           This is a more general replacement for the deprecated --workaround-gcc296-bugs option.
           When specified, it causes Memcheck not to report errors for accesses at the specified
           offsets below the stack pointer. The two offsets must be positive decimal numbers and
           -- somewhat counterintuitively -- the first one must be larger, in order to imply a
           non-wraparound address range to ignore. For example, to ignore 4 byte accesses at 8192
           bytes below the stack pointer, use --ignore-range-below-sp=8192-8189. Only one range
           may be specified.

       --show-mismatched-frees=<yes|no> [default: yes]
           When enabled, Memcheck checks that heap blocks are deallocated using a function that
           matches the allocating function. That is, it expects free to be used to deallocate
           blocks allocated by malloc, delete for blocks allocated by new, and delete[] for
           blocks allocated by new[]. If a mismatch is detected, an error is reported. This is in
           general important because in some environments, freeing with a non-matching function
           can cause crashes.

           There is however a scenario where such mismatches cannot be avoided. That is when the
           user provides implementations of new/new[] that call malloc and of delete/delete[]
           that call free, and these functions are asymmetrically inlined. For example, imagine
           that delete[] is inlined but new[] is not. The result is that Memcheck "sees" all
           delete[] calls as direct calls to free, even when the program source contains no
           mismatched calls.

           This causes a lot of confusing and irrelevant error reports.
           --show-mismatched-frees=no disables these checks. It is not generally advisable to
           disable them, though, because you may miss real errors as a result.

           Any ranges listed in this option (and multiple ranges can be specified, separated by
           commas) will be ignored by Memcheck's addressability checking.

           Fills blocks allocated by malloc, new, etc, but not by calloc, with the specified
           byte. This can be useful when trying to shake out obscure memory corruption problems.
           The allocated area is still regarded by Memcheck as undefined -- this option only
           affects its contents. Note that --malloc-fill does not affect a block of memory when
           it is used as argument to client requests VALGRIND_MEMPOOL_ALLOC or

           Fills blocks freed by free, delete, etc, with the specified byte value. This can be
           useful when trying to shake out obscure memory corruption problems. The freed area is
           still regarded by Memcheck as not valid for access -- this option only affects its
           contents. Note that --free-fill does not affect a block of memory when it is used as
           argument to client requests VALGRIND_MEMPOOL_FREE or VALGRIND_FREELIKE_BLOCK.


       --I1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1 instruction cache.

       --D1=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the level 1 data cache.

       --LL=<size>,<associativity>,<line size>
           Specify the size, associativity and line size of the last-level cache.

       --cache-sim=no|yes [yes]
           Enables or disables collection of cache access and miss counts.

       --branch-sim=no|yes [no]
           Enables or disables collection of branch instruction and misprediction counts. By
           default this is disabled as it slows Cachegrind down by approximately 25%. Note that
           you cannot specify --cache-sim=no and --branch-sim=no together, as that would leave
           Cachegrind with no information to collect.

           Write the profile data to file rather than to the default output file,
           cachegrind.out.<pid>. The %p and %q format specifiers can be used to embed the process
           ID and/or the contents of an environment variable in the name, as is the case for the
           core option --log-file.


           Write the profile data to file rather than to the default output file,
           callgrind.out.<pid>. The %p and %q format specifiers can be used to embed the process
           ID and/or the contents of an environment variable in the name, as is the case for the
           core option --log-file. When multiple dumps are made, the file name is modified
           further; see below.

       --dump-line=<no|yes> [default: yes]
           This specifies that event counting should be performed at source line granularity.
           This allows source annotation for sources which are compiled with debug information

       --dump-instr=<no|yes> [default: no]
           This specifies that event counting should be performed at per-instruction granularity.
           This allows for assembly code annotation. Currently the results can only be displayed
           by KCachegrind.

       --compress-strings=<no|yes> [default: yes]
           This option influences the output format of the profile data. It specifies whether
           strings (file and function names) should be identified by numbers. This shrinks the
           file, but makes it more difficult for humans to read (which is not recommended in any

       --compress-pos=<no|yes> [default: yes]
           This option influences the output format of the profile data. It specifies whether
           numerical positions are always specified as absolute values or are allowed to be
           relative to previous numbers. This shrinks the file size.

       --combine-dumps=<no|yes> [default: no]
           When enabled, when multiple profile data parts are to be generated these parts are
           appended to the same output file. Not recommended.

       --dump-every-bb=<count> [default: 0, never]
           Dump profile data every count basic blocks. Whether a dump is needed is only checked
           when Valgrind's internal scheduler is run. Therefore, the minimum setting useful is
           about 100000. The count is a 64-bit value to make long dump periods possible.

           Dump when entering function.

           Zero all costs when entering function.

           Dump when leaving function.

       --instr-atstart=<yes|no> [default: yes]
           Specify if you want Callgrind to start simulation and profiling from the beginning of
           the program. When set to no, Callgrind will not be able to collect any information,
           including calls, but it will have at most a slowdown of around 4, which is the minimum
           Valgrind overhead. Instrumentation can be interactively enabled via callgrind_control
           -i on.

           Note that the resulting call graph will most probably not contain main, but will
           contain all the functions executed after instrumentation was enabled. Instrumentation
           can also be programmatically enabled/disabled. See the Callgrind include file
           callgrind.h for the macro you have to use in your source code.

           For cache simulation, results will be less accurate when switching on instrumentation
           later in the program run, as the simulator starts with an empty cache at that moment.
           Switch on event collection later to cope with this error.

       --collect-atstart=<yes|no> [default: yes]
           Specify whether event collection is enabled at beginning of the profile run.

           To only look at parts of your program, you have two possibilities:

            1. Zero event counters before entering the program part you want to profile, and dump
               the event counters to a file after leaving that program part.

            2. Switch on/off collection state as needed to only see event counters happening
               while inside of the program part you want to profile.

           The second option can be used if the program part you want to profile is called many
           times. Option 1, i.e. creating a lot of dumps is not practical here.

           Collection state can be toggled at entry and exit of a given function with the option
           --toggle-collect. If you use this option, collection state should be disabled at the
           beginning. Note that the specification of --toggle-collect implicitly sets

           Collection state can be toggled also by inserting the client request
           CALLGRIND_TOGGLE_COLLECT ; at the needed code positions.

           Toggle collection on entry/exit of function.

       --collect-jumps=<no|yes> [default: no]
           This specifies whether information for (conditional) jumps should be collected. As
           above, callgrind_annotate currently is not able to show you the data. You have to use
           KCachegrind to get jump arrows in the annotated code.

       --collect-systime=<no|yes> [default: no]
           This specifies whether information for system call times should be collected.

       --collect-bus=<no|yes> [default: no]
           This specifies whether the number of global bus events executed should be collected.
           The event type "Ge" is used for these events.

       --cache-sim=<yes|no> [default: no]
           Specify if you want to do full cache simulation. By default, only instruction read
           accesses will be counted ("Ir"). With cache simulation, further event counters are
           enabled: Cache misses on instruction reads ("I1mr"/"ILmr"), data read accesses ("Dr")
           and related cache misses ("D1mr"/"DLmr"), data write accesses ("Dw") and related cache
           misses ("D1mw"/"DLmw"). For more information, see Cachegrind: a cache and branch-
           prediction profiler.

       --branch-sim=<yes|no> [default: no]
           Specify if you want to do branch prediction simulation. Further event counters are
           enabled: Number of executed conditional branches and related predictor misses
           ("Bc"/"Bcm"), executed indirect jumps and related misses of the jump address predictor


       --free-is-write=no|yes [default: no]
           When enabled (not the default), Helgrind treats freeing of heap memory as if the
           memory was written immediately before the free. This exposes races where memory is
           referenced by one thread, and freed by another, but there is no observable
           synchronisation event to ensure that the reference happens before the free.

           This functionality is new in Valgrind 3.7.0, and is regarded as experimental. It is
           not enabled by default because its interaction with custom memory allocators is not
           well understood at present. User feedback is welcomed.

       --track-lockorders=no|yes [default: yes]
           When enabled (the default), Helgrind performs lock order consistency checking. For
           some buggy programs, the large number of lock order errors reported can become
           annoying, particularly if you're only interested in race errors. You may therefore
           find it helpful to disable lock order checking.

       --history-level=none|approx|full [default: full]
           --history-level=full (the default) causes Helgrind collects enough information about
           "old" accesses that it can produce two stack traces in a race report -- both the stack
           trace for the current access, and the trace for the older, conflicting access. To
           limit memory usage, "old" accesses stack traces are limited to a maximum of 8 entries,
           even if --num-callers value is bigger.

           Collecting such information is expensive in both speed and memory, particularly for
           programs that do many inter-thread synchronisation events (locks, unlocks, etc).
           Without such information, it is more difficult to track down the root causes of races.
           Nonetheless, you may not need it in situations where you just want to check for the
           presence or absence of races, for example, when doing regression testing of a
           previously race-free program.

           --history-level=none is the opposite extreme. It causes Helgrind not to collect any
           information about previous accesses. This can be dramatically faster than

           --history-level=approx provides a compromise between these two extremes. It causes
           Helgrind to show a full trace for the later access, and approximate information
           regarding the earlier access. This approximate information consists of two stacks, and
           the earlier access is guaranteed to have occurred somewhere between program points
           denoted by the two stacks. This is not as useful as showing the exact stack for the
           previous access (as --history-level=full does), but it is better than nothing, and it
           is almost as fast as --history-level=none.

       --delta-stacktrace=no|yes [default: yes on linux amd64/x86]
           This flag only has any effect at --history-level=full.

           --delta-stacktrace configures the way Helgrind captures the stacktraces for the option
           --history-level=full. Such a stacktrace is typically needed each time a new piece of
           memory is read or written in a basic block of instructions.

           --delta-stacktrace=no causes Helgrind to compute a full history stacktrace from the
           unwind info each time a stacktrace is needed.

           --delta-stacktrace=yes indicates to Helgrind to derive a new stacktrace from the
           previous stacktrace, as long as there was no call instruction, no return instruction,
           or any other instruction changing the call stack since the previous stacktrace was
           captured. If no such instruction was executed, the new stacktrace can be derived from
           the previous stacktrace by just changing the top frame to the current program counter.
           This option can speed up Helgrind by 25% when using --history-level=full.

           The following aspects have to be considered when using --delta-stacktrace=yes :

           •   In some cases (for example in a function prologue), the
                           valgrind unwinder might not properly unwind the stack, due to some
                           limitations and/or due to wrong unwind info. When using
                           --delta-stacktrace=yes, the wrong stack trace captured in the
                           function prologue will be kept till the next call or return.

               •   On the other hand, --delta-stacktrace=yes sometimes helps to
                               obtain a correct stacktrace, for example when the unwind info
                               a correct stacktrace to be done in the beginning of the sequence,
                               but not later on in the instruction sequence..RE

                   •   Determining which instructions are changing the callstack is
                                   partially based on platform dependent heuristics, which have
                       to be
                                   tuned/validated specifically for the platform. Also, unwinding
                       in a
                                   function prologue must be good enough to allow using
                                   --delta-stacktrace=yes. Currently, the option
                                   has been reasonably validated only on linux x86 32 bits and
                                   amd64 64 bits. For more details about how to validate
                                   --delta-stacktrace=yes, see debug option --hg-sanity-flags and
                                   function check_cached_rcec_ok in libhb_core.c..RE

                   --conflict-cache-size=N [default: 1000000]
                       This flag only has any effect at --history-level=full.

                       Information about "old" conflicting accesses is stored in a cache of
                       limited size, with LRU-style management. This is necessary because it
                       isn't practical to store a stack trace for every single memory access made
                       by the program. Historical information on not recently accessed locations
                       is periodically discarded, to free up space in the cache.

                       This option controls the size of the cache, in terms of the number of
                       different memory addresses for which conflicting access information is
                       stored. If you find that Helgrind is showing race errors with only one
                       stack instead of the expected two stacks, try increasing this value.

                       The minimum value is 10,000 and the maximum is 30,000,000 (thirty times
                       the default value). Increasing the value by 1 increases Helgrind's memory
                       requirement by very roughly 100 bytes, so the maximum value will easily
                       eat up three extra gigabytes or so of memory.

                   --check-stack-refs=no|yes [default: yes]
                       By default Helgrind checks all data memory accesses made by your program.
                       This flag enables you to skip checking for accesses to thread stacks
                       (local variables). This can improve performance, but comes at the cost of
                       missing races on stack-allocated data.

                   --ignore-thread-creation=<yes|no> [default: no]
                       Controls whether all activities during thread creation should be ignored.
                       By default enabled only on Solaris. Solaris provides higher throughput,
                       parallelism and scalability than other operating systems, at the cost of
                       more fine-grained locking activity. This means for example that when a
                       thread is created under glibc, just one big lock is used for all thread
                       setup. Solaris libc uses several fine-grained locks and the creator thread
                       resumes its activities as soon as possible, leaving for example stack and
                       TLS setup sequence to the created thread. This situation confuses Helgrind
                       as it assumes there is some false ordering in place between creator and
                       created thread; and therefore many types of race conditions in the
                       application would not be reported. To prevent such false ordering, this
                       command line option is set to yes by default on Solaris. All activity
                       (loads, stores, client requests) is therefore ignored during:

                       •   pthread_create() call in the creator thread

                       •   thread creation phase (stack and TLS setup) in the created thread

                       Also new memory allocated during thread creation is untracked, that is
                       race reporting is suppressed there. DRD does the same thing implicitly.
                       This is necessary because Solaris libc caches many objects and reuses them
                       for different threads and that confuses Helgrind.


       --check-stack-var=<yes|no> [default: no]
           Controls whether DRD detects data races on stack variables. Verifying stack variables
           is disabled by default because most programs do not share stack variables over

       --exclusive-threshold=<n> [default: off]
           Print an error message if any mutex or writer lock has been held longer than the time
           specified in milliseconds. This option enables the detection of lock contention.

       --join-list-vol=<n> [default: 10]
           Data races that occur between a statement at the end of one thread and another thread
           can be missed if memory access information is discarded immediately after a thread has
           been joined. This option allows one to specify for how many joined threads memory
           access information should be retained.

        --first-race-only=<yes|no> [default: no]
           Whether to report only the first data race that has been detected on a memory location
           or all data races that have been detected on a memory location.

        --free-is-write=<yes|no> [default: no]
           Whether to report races between accessing memory and freeing memory. Enabling this
           option may cause DRD to run slightly slower. Notes:

           •   Don't enable this option when using custom memory allocators that use the
               VG_USERREQ__MALLOCLIKE_BLOCK and VG_USERREQ__FREELIKE_BLOCK because that would
               result in false positives.

           •   Don't enable this option when using reference-counted objects because that will
               result in false positives, even when that code has been annotated properly with
               ANNOTATE_HAPPENS_BEFORE and ANNOTATE_HAPPENS_AFTER. See e.g. the output of the
               following command for an example: valgrind --tool=drd --free-is-write=yes

        --report-signal-unlocked=<yes|no> [default: yes]
           Whether to report calls to pthread_cond_signal and pthread_cond_broadcast where the
           mutex associated with the signal through pthread_cond_wait or
           pthread_cond_timed_waitis not locked at the time the signal is sent. Sending a signal
           without holding a lock on the associated mutex is a common programming error which can
           cause subtle race conditions and unpredictable behavior. There exist some uncommon
           synchronization patterns however where it is safe to send a signal without holding a
           lock on the associated mutex.

       --segment-merging=<yes|no> [default: yes]
           Controls segment merging. Segment merging is an algorithm to limit memory usage of the
           data race detection algorithm. Disabling segment merging may improve the accuracy of
           the so-called 'other segments' displayed in race reports but can also trigger an out
           of memory error.

       --segment-merging-interval=<n> [default: 10]
           Perform segment merging only after the specified number of new segments have been
           created. This is an advanced configuration option that allows one to choose whether to
           minimize DRD's memory usage by choosing a low value or to let DRD run faster by
           choosing a slightly higher value. The optimal value for this parameter depends on the
           program being analyzed. The default value works well for most programs.

       --shared-threshold=<n> [default: off]
           Print an error message if a reader lock has been held longer than the specified time
           (in milliseconds). This option enables the detection of lock contention.

       --show-confl-seg=<yes|no> [default: yes]
           Show conflicting segments in race reports. Since this information can help to find the
           cause of a data race, this option is enabled by default. Disabling this option makes
           the output of DRD more compact.

       --show-stack-usage=<yes|no> [default: no]
           Print stack usage at thread exit time. When a program creates a large number of
           threads it becomes important to limit the amount of virtual memory allocated for
           thread stacks. This option makes it possible to observe how much stack memory has been
           used by each thread of the client program. Note: the DRD tool itself allocates some
           temporary data on the client thread stack. The space necessary for this temporary data
           must be allocated by the client program when it allocates stack memory, but is not
           included in stack usage reported by DRD.

       --ignore-thread-creation=<yes|no> [default: no]
           Controls whether all activities during thread creation should be ignored. By default
           enabled only on Solaris. Solaris provides higher throughput, parallelism and
           scalability than other operating systems, at the cost of more fine-grained locking
           activity. This means for example that when a thread is created under glibc, just one
           big lock is used for all thread setup. Solaris libc uses several fine-grained locks
           and the creator thread resumes its activities as soon as possible, leaving for example
           stack and TLS setup sequence to the created thread. This situation confuses DRD as it
           assumes there is some false ordering in place between creator and created thread; and
           therefore many types of race conditions in the application would not be reported. To
           prevent such false ordering, this command line option is set to yes by default on
           Solaris. All activity (loads, stores, client requests) is therefore ignored during:

           •   pthread_create() call in the creator thread

           •   thread creation phase (stack and TLS setup) in the created thread

       --trace-addr=<address> [default: none]
           Trace all load and store activity for the specified address. This option may be
           specified more than once.

       --ptrace-addr=<address> [default: none]
           Trace all load and store activity for the specified address and keep doing that even
           after the memory at that address has been freed and reallocated.

       --trace-alloc=<yes|no> [default: no]
           Trace all memory allocations and deallocations. May produce a huge amount of output.

       --trace-barrier=<yes|no> [default: no]
           Trace all barrier activity.

       --trace-cond=<yes|no> [default: no]
           Trace all condition variable activity.

       --trace-fork-join=<yes|no> [default: no]
           Trace all thread creation and all thread termination events.

       --trace-hb=<yes|no> [default: no]
           Trace execution of the ANNOTATE_HAPPENS_BEFORE(), ANNOTATE_HAPPENS_AFTER() and
           ANNOTATE_HAPPENS_DONE() client requests.

       --trace-mutex=<yes|no> [default: no]
           Trace all mutex activity.

       --trace-rwlock=<yes|no> [default: no]
           Trace all reader-writer lock activity.

       --trace-semaphore=<yes|no> [default: no]
           Trace all semaphore activity.


       --heap=<yes|no> [default: yes]
           Specifies whether heap profiling should be done.

       --heap-admin=<size> [default: 8]
           If heap profiling is enabled, gives the number of administrative bytes per block to
           use. This should be an estimate of the average, since it may vary. For example, the
           allocator used by glibc on Linux requires somewhere between 4 to 15 bytes per block,
           depending on various factors. That allocator also requires admin space for freed
           blocks, but Massif cannot account for this.

       --stacks=<yes|no> [default: no]
           Specifies whether stack profiling should be done. This option slows Massif down
           greatly, and so is off by default. Note that Massif assumes that the main stack has
           size zero at start-up. This is not true, but doing otherwise accurately is difficult.
           Furthermore, starting at zero better indicates the size of the part of the main stack
           that a user program actually has control over.

       --pages-as-heap=<yes|no> [default: no]
           Tells Massif to profile memory at the page level rather than at the malloc'd block
           level. See above for details.

       --depth=<number> [default: 30]
           Maximum depth of the allocation trees recorded for detailed snapshots. Increasing it
           will make Massif run somewhat more slowly, use more memory, and produce bigger output

           Functions specified with this option will be treated as though they were a heap
           allocation function such as malloc. This is useful for functions that are wrappers to
           malloc or new, which can fill up the allocation trees with uninteresting information.
           This option can be specified multiple times on the command line, to name multiple

           Note that the named function will only be treated this way if it is the top entry in a
           stack trace, or just below another function treated this way. For example, if you have
           a function malloc1 that wraps malloc, and malloc2 that wraps malloc1, just specifying
           --alloc-fn=malloc2 will have no effect. You need to specify --alloc-fn=malloc1 as
           well. This is a little inconvenient, but the reason is that checking for allocation
           functions is slow, and it saves a lot of time if Massif can stop looking through the
           stack trace entries as soon as it finds one that doesn't match rather than having to
           continue through all the entries.

           Note that C++ names are demangled. Note also that overloaded C++ names must be written
           in full. Single quotes may be necessary to prevent the shell from breaking them up.
           For example:

               --alloc-fn='operator new(unsigned, std::nothrow_t const&)'

           Any direct heap allocation (i.e. a call to malloc, new, etc, or a call to a function
           named by an --alloc-fn option) that occurs in a function specified by this option will
           be ignored. This is mostly useful for testing purposes. This option can be specified
           multiple times on the command line, to name multiple functions.

           Any realloc of an ignored block will also be ignored, even if the realloc call does
           not occur in an ignored function. This avoids the possibility of negative heap sizes
           if ignored blocks are shrunk with realloc.

           The rules for writing C++ function names are the same as for --alloc-fn above.

       --threshold=<m.n> [default: 1.0]
           The significance threshold for heap allocations, as a percentage of total memory size.
           Allocation tree entries that account for less than this will be aggregated. Note that
           this should be specified in tandem with ms_print's option of the same name.

       --peak-inaccuracy=<m.n> [default: 1.0]
           Massif does not necessarily record the actual global memory allocation peak; by
           default it records a peak only when the global memory allocation size exceeds the
           previous peak by at least 1.0%. This is because there can be many local allocation
           peaks along the way, and doing a detailed snapshot for every one would be expensive
           and wasteful, as all but one of them will be later discarded. This inaccuracy can be
           changed (even to 0.0%) via this option, but Massif will run drastically slower as the
           number approaches zero.

       --time-unit=<i|ms|B> [default: i]
           The time unit used for the profiling. There are three possibilities: instructions
           executed (i), which is good for most cases; real (wallclock) time (ms, i.e.
           milliseconds), which is sometimes useful; and bytes allocated/deallocated on the heap
           and/or stack (B), which is useful for very short-run programs, and for testing
           purposes, because it is the most reproducible across different machines.

       --detailed-freq=<n> [default: 10]
           Frequency of detailed snapshots. With --detailed-freq=1, every snapshot is detailed.

       --max-snapshots=<n> [default: 100]
           The maximum number of snapshots recorded. If set to N, for all programs except very
           short-running ones, the final number of snapshots will be between N/2 and N.

       --massif-out-file=<file> [default: massif.out.%p]
           Write the profile data to file rather than to the default output file,
           massif.out.<pid>. The %p and %q format specifiers can be used to embed the process ID
           and/or the contents of an environment variable in the name, as is the case for the
           core option --log-file.


       There are no SGCheck-specific command-line options at present.


       --bb-out-file=<name> [default: bb.out.%p]
           This option selects the name of the basic block vector file. The %p and %q format
           specifiers can be used to embed the process ID and/or the contents of an environment
           variable in the name, as is the case for the core option --log-file.

       --pc-out-file=<name> [default: pc.out.%p]
           This option selects the name of the PC file. This file holds program counter addresses
           and function name info for the various basic blocks. This can be used in conjunction
           with the basic block vector file to fast-forward via function names instead of just
           instruction counts. The %p and %q format specifiers can be used to embed the process
           ID and/or the contents of an environment variable in the name, as is the case for the
           core option --log-file.

       --interval-size=<number> [default: 100000000]
           This option selects the size of the interval to use. The default is 100 million
           instructions, which is a commonly used value. Other sizes can be used; smaller
           intervals can help programs with finer-grained phases. However smaller interval size
           can lead to accuracy issues due to warm-up effects (When fast-forwarding the various
           architectural features will be un-initialized, and it will take some number of
           instructions before they "warm up" to the state a full simulation would be at without
           the fast-forwarding. Large interval sizes tend to mitigate this.)

       --instr-count-only [default: no]
           This option tells the tool to only display instruction count totals, and to not
           generate the actual basic block vector file. This is useful for debugging, and for
           gathering instruction count info without generating the large basic block vector


       --basic-counts=<no|yes> [default: yes]
           When enabled, Lackey prints the following statistics and information about the
           execution of the client program:

            1. The number of calls to the function specified by the --fnname option (the default
               is main). If the program has had its symbols stripped, the count will always be

            2. The number of conditional branches encountered and the number and proportion of
               those taken.

            3. The number of superblocks entered and completed by the program. Note that due to
               optimisations done by the JIT, this is not at all an accurate value.

            4. The number of guest (x86, amd64, ppc, etc.) instructions and IR statements
               executed. IR is Valgrind's RISC-like intermediate representation via which all
               instrumentation is done.

            5. Ratios between some of these counts.

            6. The exit code of the client program.

       --detailed-counts=<no|yes> [default: no]
           When enabled, Lackey prints a table containing counts of loads, stores and ALU
           operations, differentiated by their IR types. The IR types are identified by their IR
           name ("I1", "I8", ... "I128", "F32", "F64", and "V128").

       --trace-mem=<no|yes> [default: no]
           When enabled, Lackey prints the size and address of almost every memory access made by
           the program. See the comments at the top of the file lackey/lk_main.c for details
           about the output format, how it works, and inaccuracies in the address trace. Note
           that this option produces immense amounts of output.

       --trace-superblocks=<no|yes> [default: no]
           When enabled, Lackey prints out the address of every superblock (a single entry,
           multiple exit, linear chunk of code) executed by the program. This is primarily of
           interest to Valgrind developers. See the comments at the top of the file
           lackey/lk_main.c for details about the output format. Note that this option produces
           large amounts of output.

       --fnname=<name> [default: main]
           Changes the function for which calls are counted when --basic-counts=yes is specified.


       cg_annotate(1), callgrind_annotate(1), callgrind_control(1), ms_print(1),
       $INSTALL/share/doc/valgrind/html/index.html or, Debugging your program using Valgrind's
       gdbserver and GDB[1] vgdb[2], Valgrind monitor commands[3], The Commentary[4], Scheduling
       and Multi-Thread Performance[5], Cachegrind: a cache and branch-prediction profiler[6].


       See the AUTHORS file in the valgrind distribution for a comprehensive list of authors.

       This manpage was written by Andres Roldan <> and the Valgrind


        1. Debugging your program using Valgrind's gdbserver and GDB

        2. vgdb

        3. Valgrind monitor commands

        4. The Commentary

        5. Scheduling and Multi-Thread Performance

        6. Cachegrind: a cache and branch-prediction profiler