Provided by: mono-runtime-common_4.6.2.7+dfsg-1ubuntu1_amd64 
NAME
mono - Mono's ECMA-CLI native code generator (Just-in-Time and Ahead-of-Time)
SYNOPSIS
mono [options] file [arguments...]
mono-sgen [options] file [arguments...]
DESCRIPTION
mono is a runtime implementation of the ECMA Common Language Infrastructure. This can be used to run
ECMA and .NET applications.
The runtime contains a native code generator that transforms the Common Intermediate Language into native
code.
The code generator can operate in two modes: just in time compilation (JIT) or ahead of time compilation
(AOT). Since code can be dynamically loaded, the runtime environment and the JIT are always present,
even if code is compiled ahead of time.
The runtime loads the specified file and optionally passes the arguments to it. The file is an ECMA
assembly. They typically have a .exe or .dll extension.
The runtime provides a number of configuration options for running applications, for developing and
debugging, and for testing and debugging the runtime itself.
The mono command uses the Boehm conservative garbage collector while the mono-sgen command uses a moving
and generational garbage collector.
PORTABILITY
On Unix-based systems, Mono provides a mechanism to emulate the Windows-style file access, this includes
providing a case insensitive view of the file system, directory separator mapping (from \ to /) and
stripping the drive letters.
This functionality is enabled by setting the MONO_IOMAP environment variable to one of all, drive and
case.
See the description for MONO_IOMAP in the environment variables section for more details.
RUNTIME OPTIONS
The following options are available:
--aot, --aot[=options]
This option is used to precompile the CIL code in the specified assembly to native code. The
generated code is stored in a file with the extension .so. This file will be automatically picked
up by the runtime when the assembly is executed. Ahead-of-Time compilation is most useful if you
use it in combination with the -O=all,-shared flag which enables all of the optimizations in the
code generator to be performed. Some of those optimizations are not practical for Just-in-Time
compilation since they might be very time consuming. Unlike the .NET Framework, Ahead-of-Time
compilation will not generate domain independent code: it generates the same code that the Just-
in-Time compiler would produce. Since most applications use a single domain, this is fine. If
you want to optimize the generated code for use in multi-domain applications, consider using the
-O=shared flag. This pre-compiles the methods, but the original assembly is still required to
execute as this one contains the metadata and exception information which is not available on the
generated file. When precompiling code, you might want to compile with all optimizations
(-O=all). Pre-compiled code is position independent code. Pre compilation is just a mechanism to
reduce startup time, increase code sharing across multiple mono processes and avoid just-in-time
compilation program startup costs. The original assembly must still be present, as the metadata
is contained there. AOT code typically can not be moved from one computer to another (CPU-
specific optimizations that are detected at runtime) so you should not try to move the pre-
generated assemblies or package the pre-generated assemblies for deployment. A few options are
available as a parameter to the --aot command line option. The options are separated by commas,
and more than one can be specified:
autoreg
The AOT compiler will emit a (ELF only) library initializer to automatically register the
aot compiled module with the runtime. This is only useful in static mode
asmonly
Instructs the AOT compiler to output assembly code instead of an object file.
bind-to-runtime-version
If specified, forces the generated AOT files to be bound to the runtime version of the
compiling Mono. This will prevent the AOT files from being consumed by a different Mono
runtime. full This is currently an experimental feature as it is not complete. This
instructs Mono to precompile code that has historically not been precompiled with AOT.
data-outfile=FILE.dll.aotdata
This instructs the AOT code generator to output certain data constructs into a separate
file. This can reduce the executable images some five to twenty percent. Developers
need to then ship the resulting aotdata as a resource and register a hook to load the data
on demand by using the mono_install_load_aot_data_hook method.
direct-pinvoke
When this option is specified, P/Invoke methods are invoked directly instead of going
through the operating system symbol lookup operation.
llvm-path=<PREFIX>
Same for the llvm tools 'opt' and 'llc'.
msym-dir=<PATH>
Instructs the AOT compiler to generate offline sequence points .msym files. The generated
.msym files will be stored into a subfolder of <PATH> named as the compilation AOTID.
mtriple=<TRIPLE>
Use the GNU style target triple <TRIPLE> to determine some code generation options, i.e.
--mtriple=armv7-linux-gnueabi will generate code that targets ARMv7. This is currently only
supported by the ARM backend. In LLVM mode, this triple is passed on to the LLVM llc
compiler.
nimt-trampolines=[number]
When compiling in full aot mode, the IMT trampolines must be precreated in the AOT image.
You can add additional method trampolines with this argument. Defaults to 128.
nodebug
Instructs the AOT compiler to not output any debugging information.
no-direct-calls
This prevents the AOT compiler from generating a direct calls to a method. The AOT
compiler usually generates direct calls for certain methods that do not require going
through the PLT (for example, methods that are known to not require a hook like a static
constructor) or call into simple internal calls.
dwarfdebug
Instructs the AOT compiler to emit DWARF debugging information. When used together with the
nodebug option, only DWARF debugging information is emitted, but not the information that
can be used at runtime.
nrgctx-trampolines=[number]
When compiling in full aot mode, the generic sharing trampolines must be precreated in the
AOT image. You can add additional method trampolines with this argument. Defaults to
1024.
ntrampolines=[number]
When compiling in full aot mode, the method trampolines must be precreated in the AOT
image. You can add additional method trampolines with this argument. Defaults to 1024.
outfile=[filename]
Instructs the AOT compiler to save the output to the specified file.
print-skipped-methods
If the AOT compiler cannot compile a method for any reason, enabling this flag will output
the skipped methods to the console.
readonly-value=namespace.typename.fieldname=type/value
Override the value of a static readonly field. Usually, during JIT compilation, the static
constructor is ran eagerly, so the value of a static readonly field is known at compilation
time and the compiler can do a number of optimizations based on it. During AOT, instead,
the static constructor can't be ran, so this option can be used to set the value of such a
field and enable the same set of optimizations. Type can be any of i1, i2, i4 for integers
of the respective sizes (in bytes). Note that signed/unsigned numbers do not matter here,
just the storage size. This option can be specified multiple times and it doesn't prevent
the static constructor for the type defining the field to execute with the usual rules at
runtime (hence possibly computing a different value for the field).
save-temps,keep-temps
Instructs the AOT compiler to keep temporary files.
soft-debug
This instructs the compiler to generate sequence point checks that allow Mono's soft
debugger to debug applications even on systems where it is not possible to set breakpoints
or to single step (certain hardware configurations like the cell phones and video gaming
consoles).
static Create an ELF object file (.o) or .s file which can be statically linked into an executable
when embedding the mono runtime. When this option is used, the object file needs to be
registered with the embedded runtime using the mono_aot_register_module function which
takes as its argument the mono_aot_module_<ASSEMBLY NAME>_info global symbol from the
object file:
extern void *mono_aot_module_hello_info;
mono_aot_register_module (mono_aot_module_hello_info);
stats Print various stats collected during AOT compilation.
threads=[number]
This is an experimental option for the AOT compiler to use multiple threads when compiling
the methods.
tool-prefix=<PREFIX>
Prepends <PREFIX> to the name of tools ran by the AOT compiler, i.e. 'as'/'ld'. For
example, --tool=prefix=arm-linux-gnueabi- will make the AOT compiler run
write-symbols
Instructs the AOT compiler to emit debug symbol information.
For more information about AOT, see: http://www.mono-project.com/docs/advanced/aot/
--attach=[options]
Currently the only option supported by this command line argument is disable which disables the
attach functionality.
--config filename
Load the specified configuration file instead of the default one(s). The default files are
/etc/mono/config and ~/.mono/config or the file specified in the MONO_CONFIG environment variable,
if set. See the mono-config(5) man page for details on the format of this file.
--debugger-agent=[options]
This instructs the Mono runtime to start a debugging agent inside the Mono runtime and connect it
to a client user interface will control the Mono process. This option is typically used by IDEs,
like the MonoDevelop IDE.
The configuration is specified using one of more of the following options:
address=host:port
Use this option to specify the IP address where your debugger client is listening to.
loglevel=LEVEL
Specifies the diagnostics log level for
logfile=filename
Used to specify the file where the log will be stored, it defaults to standard output.
server=[y/n]
Defaults to no, with the default option Mono will actively connect to the host/port
configured with the address option. If you set it to 'y', it instructs the Mono runtime to
start debugging in server mode, where Mono actively waits for the debugger front end to
connect to the Mono process. Mono will print out to stdout the IP address and port where
it is listening.
setpgid=[y/n]
If set to yes, Mono will call setpgid(0, 0) on startup, if that function is available on
the system. This is useful for ensuring that signals delivered to a process that is
executing the debuggee are not propagated to the debuggee, e.g. when Ctrl-C sends SIGINT to
the sdb tool.
suspend=[y/n]
Defaults to yes, with the default option Mono will suspend the vm on startup until it
connects successfully to a debugger front end. If you set it to 'n', in conjunction with
server=y, it instructs the Mono runtime to run as normal, while caching metadata to send to
the debugger front end on connection..
transport=transport_name
This is used to specify the transport that the debugger will use to communicate. It must
be specified and currently requires this to be 'dt_socket'.
--desktop
Configures the virtual machine to be better suited for desktop applications. Currently this sets
the GC system to avoid expanding the heap as much as possible at the expense of slowing down
garbage collection a bit.
--full-aot
This is an experimental flag that instructs the Mono runtime to not generate any code at runtime
and depend exclusively on the code generated from using mono --aot=full previously. This is
useful for platforms that do not permit dynamic code generation. Notice that this feature will
abort execution at runtime if a codepath in your program, or Mono's class libraries attempts to
generate code dynamically. You should test your software upfront and make sure that you do not
use any dynamic features.
--gc=boehm, --gc=sgen
Selects the Garbage Collector engine for Mono to use, Boehm or SGen. Currently this merely
ensures that you are running either the mono or mono-sgen commands. This flag can be set in the
MONO_ENV_OPTIONS environment variable to force all of your child processes to use one particular
kind of GC with the Mono runtime.
--arch=32, --arch=64
(Mac OS X only): Selects the bitness of the Mono binary used, if available. If the binary used is
already for the selected bitness, nothing changes. If not, the execution switches to a binary with
the selected bitness suffix installed side by side (for example, '/bin/mono --arch=64' will switch
to '/bin/mono64' iff '/bin/mono' is a 32-bit build).
--help, -h
Displays usage instructions.
--llvm If the Mono runtime has been compiled with LLVM support (not available in all configurations),
Mono will use the LLVM optimization and code generation engine to JIT or AOT compile. For more
information, consult: http://www.mono-project.com/docs/advanced/mono-llvm/
--nollvm
When using a Mono that has been compiled with LLVM support, it forces Mono to fallback to its JIT
engine and not use the LLVM backend.
--optimize=MODE, -O=MODE
MODE is a comma separated list of optimizations. They also allow optimizations to be turned off
by prefixing the optimization name with a minus sign. In general, Mono has been tuned to use the
default set of flags, before using these flags for a deployment setting, you might want to
actually measure the benefits of using them. The following optimization flags are implemented in
the core engine:
abcrem Array bound checks removal
all Turn on all optimizations
aot Usage of Ahead Of Time compiled code
branch Branch optimizations
cfold Constant folding
cmov Conditional moves [arch-dependency]
deadce Dead code elimination
consprop Constant propagation
copyprop Copy propagation
fcmov Fast x86 FP compares [arch-dependency]
float32 Perform 32-bit float arithmetic using 32-bit operations
gshared Enable generic code sharing.
inline Inline method calls
intrins Intrinsic method implementations
linears Linear scan global reg allocation
leaf Leaf procedures optimizations
loop Loop related optimizations
peephole Peephole postpass
precomp Precompile all methods before executing Main
sched Instruction scheduling
shared Emit per-domain code
sse2 SSE2 instructions on x86 [arch-dependency]
tailc Tail recursion and tail calls
For example, to enable all the optimization but dead code elimination and inlining, you can use:
-O=all,-deadce,-inline
The flags that are flagged with [arch-dependency] indicate that the given option if used in
combination with Ahead of Time compilation (--aot flag) would produce pre-compiled code that will
depend on the current CPU and might not be safely moved to another computer.
The following optimizations are supported
float32
Requests that the runtime performn 32-bit floating point operations using only 32-bits.
By default the Mono runtime tries to use the highest precision available for floating point
operations, but while this might render better results, the code might run slower. This
options also affects the code generated by the LLVM backend.
inline Controls whether the runtime should attempt to inline (the default), or not inline methods
invocations
--runtime=VERSION
Mono supports different runtime versions. The version used depends on the program that is being
run or on its configuration file (named program.exe.config). This option can be used to override
such autodetection, by forcing a different runtime version to be used. Note that this should only
be used to select a later compatible runtime version than the one the program was compiled
against. A typical usage is for running a 1.1 program on a 2.0 version:
mono --runtime=v2.0.50727 program.exe
--security, --security=mode
Activate the security manager, a currently experimental feature in Mono and it is OFF by default.
The new code verifier can be enabled with this option as well.
Using security without parameters is equivalent as calling it with the "cas" parameter.
The following modes are supported:
core-clr
Enables the core-clr security system, typically used for Moonlight/Silverlight
applications. It provides a much simpler security system than CAS, see http://www.mono-
project.com/docs/web/moonlight/ for more details and links to the descriptions of this new
system.
validil
Enables the new verifier and performs basic verification for code validity. In this mode,
unsafe code and P/Invoke are allowed. This mode provides a better safety guarantee but it
is still possible for managed code to crash Mono.
verifiable
Enables the new verifier and performs full verification of the code being executed. It
only allows verifiable code to be executed. Unsafe code is not allowed but P/Invoke is.
This mode should not allow managed code to crash mono. The verification is not as strict
as ECMA 335 standard in order to stay compatible with the MS runtime.
The security system acts on user code: code contained in mscorlib or the global assembly cache is
always trusted.
--server
Configures the virtual machine to be better suited for server operations (currently, allows a
heavier threadpool initialization).
--verify-all
Verifies mscorlib and assemblies in the global assembly cache for valid IL, and all user code for
IL verifiability.
This is different from --security's verifiable or validil in that these options only check user
code and skip mscorlib and assemblies located on the global assembly cache.
-V, --version
Prints JIT version information (system configuration, release number and branch names if
available).
DEVELOPMENT OPTIONS
The following options are used to help when developing a JITed application.
--debug, --debug=OPTIONS
Turns on the debugging mode in the runtime. If an assembly was compiled with debugging
information, it will produce line number information for stack traces.
The optional OPTIONS argument is a comma separated list of debugging options. These options are
turned off by default since they generate much larger and slower code at runtime.
The following options are supported:
casts Produces a detailed error when throwing a InvalidCastException. This option needs to be
enabled as this generates more verbose code at execution time.
mdb-optimizations
Disable some JIT optimizations which are usually only disabled when running inside the
debugger. This can be helpful if you want to attach to the running process with mdb.
gdb Generate and register debugging information with gdb. This is only supported on some
platforms, and only when using gdb 7.0 or later.
--profile[=profiler[:profiler_args]]
Turns on profiling. For more information about profiling applications and code coverage see the
sections "PROFILING" and "CODE COVERAGE" below.
This option can be used multiple times, each time will load an
additional profiler. This allows developers to use modules that extend the JIT through the Mono
profiling interface.
--trace[=expression]
Shows method names as they are invoked. By default all methods are traced. The trace can be
customized to include or exclude methods, classes or assemblies. A trace expression is a comma
separated list of targets, each target can be prefixed with a minus sign to turn off a particular
target. The words `program', `all' and `disabled' have special meaning. `program' refers to the
main program being executed, and `all' means all the method calls. The `disabled' option is used
to start up with tracing disabled. It can be enabled at a later point in time in the program by
sending the SIGUSR2 signal to the runtime. Assemblies are specified by their name, for example,
to trace all calls in the System assembly, use:
mono --trace=System app.exe
Classes are specified with the T: prefix. For example, to trace all calls to the System.String
class, use:
mono --trace=T:System.String app.exe
And individual methods are referenced with the M: prefix, and the standard method notation:
mono --trace=M:System.Console:WriteLine app.exe
Exceptions can also be traced, it will cause a stack trace to be printed every time an exception
of the specified type is thrown. The exception type can be specified with or without the
namespace, and to trace all exceptions, specify 'all' as the type name.
mono --trace=E:System.Exception app.exe
As previously noted, various rules can be specified at once:
mono --trace=T:System.String,T:System.Random app.exe
You can exclude pieces, the next example traces calls to System.String except for the
System.String:Concat method.
mono --trace=T:System.String,-M:System.String:Concat
You can trace managed to unmanaged transitions using the wrapper qualifier:
mono --trace=wrapper app.exe
Finally, namespaces can be specified using the N: prefix:
mono --trace=N:System.Xml
--no-x86-stack-align
Don't align stack frames on the x86 architecture. By default, Mono aligns stack frames to 16
bytes on x86, so that local floating point and SIMD variables can be properly aligned. This
option turns off the alignment, which usually saves one intruction per call, but might result in
significantly lower floating point and SIMD performance.
--jitmap
Generate a JIT method map in a /tmp/perf-PID.map file. This file is then used, for example, by the
perf tool included in recent Linux kernels. Each line in the file has:
HEXADDR HEXSIZE methodname
Currently this option is only supported on Linux.
JIT MAINTAINER OPTIONS
The maintainer options are only used by those developing the runtime itself, and not typically of
interest to runtime users or developers.
--bisect=optimization:filename
This flag is used by the automatic optimization bug bisector. It takes an optimization flag and a
filename of a file containing a list of full method names, one per line. When it compiles one of
the methods in the file it will use the optimization given, in addition to the optimizations that
are otherwise enabled. Note that if the optimization is enabled by default, you should disable it
with `-O`, otherwise it will just apply to every method, whether it's in the file or not.
--break method
Inserts a breakpoint before the method whose name is `method' (namespace.class:methodname). Use
`Main' as method name to insert a breakpoint on the application's main method. You can use it
also with generics, for example "System.Collections.Generic.Queue`1:Peek"
--breakonex
Inserts a breakpoint on exceptions. This allows you to debug your application with a native
debugger when an exception is thrown.
--compile name
This compiles a method (namespace.name:methodname), this is used for testing the compiler
performance or to examine the output of the code generator.
--compileall
Compiles all the methods in an assembly. This is used to test the compiler performance or to
examine the output of the code generator
--graph=TYPE METHOD
This generates a postscript file with a graph with the details about the specified method
(namespace.name:methodname). This requires `dot' and ghostview to be installed (it expects
Ghostview to be called "gv"). The following graphs are available:
cfg Control Flow Graph (CFG)
dtree Dominator Tree
code CFG showing code
ssa CFG showing code after SSA translation
optcode CFG showing code after IR optimizations
Some graphs will only be available if certain optimizations are turned on.
--ncompile
Instruct the runtime on the number of times that the method specified by --compile (or all the
methods if --compileall is used) to be compiled. This is used for testing the code generator
performance.
--stats
Displays information about the work done by the runtime during the execution of an application.
--wapi=hps|semdel
Perform maintenance of the process shared data. semdel will delete the global semaphore. hps
will list the currently used handles.
-v, --verbose
Increases the verbosity level, each time it is listed, increases the verbosity level to include
more information (including, for example, a disassembly of the native code produced, code selector
info etc.).
ATTACH SUPPORT
The Mono runtime allows external processes to attach to a running process and load assemblies into the
running program. To attach to the process, a special protocol is implemented in the Mono.Management
assembly.
With this support it is possible to load assemblies that have an entry point (they are created with
-target:exe or -target:winexe) to be loaded and executed in the Mono process.
The code is loaded into the root domain, and it starts execution on the special runtime attach thread.
The attached program should create its own threads and return after invocation.
This support allows for example debugging applications by having the csharp shell attach to running
processes.
PROFILING
The mono runtime includes a profiler that can be used to explore various performance related problems in
your application. The profiler is activated by passing the --profile command line argument to the Mono
runtime, the format is:
--profile[=profiler[:profiler_args]]
Mono has a built-in profiler called 'default' (and is also the default if no arguments are specified),
but developers can write custom profilers, see the section "CUSTOM PROFILERS" for more details.
If a profiler is not specified, the default profiler is used. The profiler_args is a profiler-specific
string of options for the profiler itself. The default profiler accepts the following options 'alloc' to
profile memory consumption by the application; 'time' to profile the time spent on each routine; 'jit' to
collect time spent JIT-compiling methods and 'stat' to perform sample statistical profiling. If no
options are provided the default is 'alloc,time,jit'.
By default the profile data is printed to stdout: to change this, use the 'file=filename' option to
output the data to filename. For example:
mono --profile program.exe
That will run the program with the default profiler and will do time and allocation profiling.
mono --profile=default:stat,alloc,file=prof.out program.exe
Will do sample statistical profiling and allocation profiling on program.exe. The profile data is put in
prof.out. Note that the statistical profiler has a very low overhead and should be the preferred
profiler to use (for better output use the full path to the mono binary when running and make sure you
have installed the addr2line utility that comes from the binutils package).
LOG PROFILER
This is the most advanced profiler.
The Mono log profiler can be used to collect a lot of information about a program running in the Mono
runtime. This data can be used (both while the process is running and later) to do analyses of the
program behaviour, determine resource usage, performance issues or even look for particular execution
patterns.
This is accomplished by logging the events provided by the Mono runtime through the profiling interface
and periodically writing them to a file which can be later inspected with the mprof-report(1) tool.
More information about how to use the log profiler is available on the mprof-report(1) page.
CUSTOM PROFILERS
Mono provides a mechanism for loading other profiling modules which in the form of shared libraries.
These profiling modules can hook up to various parts of the Mono runtime to gather information about the
code being executed.
To use a third party profiler you must pass the name of the profiler to Mono, like this:
mono --profile=custom program.exe
In the above sample Mono will load the user defined profiler from the shared library `mono-profiler-
custom.so'. This profiler module must be on your dynamic linker library path.
A list of other third party profilers is available from Mono's web site (www.mono-
project.com/docs/advanced/performance-tips/)
Custom profiles are written as shared libraries. The shared library must be called `mono-profiler-
NAME.so' where `NAME' is the name of your profiler.
For a sample of how to write your own custom profiler look in the Mono source tree for in the
samples/profiler.c.
CODE COVERAGE
Mono ships with a code coverage module. This module is activated by using the Mono --profile=cov option.
The format is: --profile=cov[:assembly-name[/namespace]] test-suite.exe
By default code coverage will default to all the assemblies loaded, you can limit this by specifying the
assembly name, for example to perform code coverage in the routines of your program use, for example the
following command line limits the code coverage to routines in the "demo" assembly:
mono --profile=cov:demo demo.exe
Notice that the assembly-name does not include the extension.
You can further restrict the code coverage output by specifying a namespace:
mono --profile=cov:demo/My.Utilities demo.exe
Which will only perform code coverage in the given assembly and namespace.
Typical output looks like this:
Not covered: Class:.ctor ()
Not covered: Class:A ()
Not covered: Driver:.ctor ()
Not covered: Driver:method ()
Partial coverage: Driver:Main ()
offset 0x000a
The offsets displayed are IL offsets.
A more powerful coverage tool is available in the module `monocov'. See the monocov(1) man page for
details.
DEBUGGING AIDS
To debug managed applications, you can use the mdb command, a command line debugger.
It is possible to obtain a stack trace of all the active threads in Mono by sending the QUIT signal to
Mono, you can do this from the command line, like this:
kill -QUIT pid
Where pid is the Process ID of the Mono process you want to examine. The process will continue running
afterwards, but its state is not guaranteed.
Important: this is a last-resort mechanism for debugging applications and should not be used to monitor
or probe a production application. The integrity of the runtime after sending this signal is not
guaranteed and the application might crash or terminate at any given point afterwards.
The --debug=casts option can be used to get more detailed information for Invalid Cast operations, it
will provide information about the types involved.
You can use the MONO_LOG_LEVEL and MONO_LOG_MASK environment variables to get verbose debugging output
about the execution of your application within Mono.
The MONO_LOG_LEVEL environment variable if set, the logging level is changed to the set value. Possible
values are "error", "critical", "warning", "message", "info", "debug". The default value is "error".
Messages with a logging level greater then or equal to the log level will be printed to stdout/stderr.
Use "info" to track the dynamic loading of assemblies.
Use the MONO_LOG_MASK environment variable to limit the extent of the messages you get: If set, the log
mask is changed to the set value. Possible values are "asm" (assembly loader), "type", "dll" (native
library loader), "gc" (garbage collector), "cfg" (config file loader), "aot" (precompiler), "security"
(e.g. Moonlight CoreCLR support), "threadpool" (thread pool generic), "io-threadpool" (thread pool I/O),
"io-layer" (I/O layer - sockets, handles, shared memory etc) and "all". The default value is "all".
Changing the mask value allows you to display only messages for a certain component. You can use multiple
masks by comma separating them. For example to see config file messages and assembly loader messages set
you mask to "asm,cfg".
The following is a common use to track down problems with P/Invoke:
$ MONO_LOG_LEVEL="debug" MONO_LOG_MASK="dll" mono glue.exe
DEBUGGING WITH LLDB
If you are using LLDB, you can use the mono.py script to print some internal data structures with it.
To use this, add this to your $HOME/.lldbinit file:
command script import $PREFIX/lib/mono/lldb/mono.py
Where $PREFIX is the prefix value that you used when you configured Mono (typically /usr).
Once this is done, then you can inspect some Mono Runtime data structures, for example:
(lldb) p method
(MonoMethod *) $0 = 0x05026ac0 [mscorlib]System.OutOfMemoryException:.ctor()
SERIALIZATION
Mono's XML serialization engine by default will use a reflection-based approach to serialize which might
be slow for continuous processing (web service applications). The serialization engine will determine
when a class must use a hand-tuned serializer based on a few parameters and if needed it will produce a
customized C# serializer for your types at runtime. This customized serializer then gets dynamically
loaded into your application.
You can control this with the MONO_XMLSERIALIZER_THS environment variable.
The possible values are `no' to disable the use of a C# customized serializer, or an integer that is the
minimum number of uses before the runtime will produce a custom serializer (0 will produce a custom
serializer on the first access, 50 will produce a serializer on the 50th use). Mono will fallback to an
interpreted serializer if the serializer generation somehow fails. This behavior can be disabled by
setting the option `nofallback' (for example: MONO_XMLSERIALIZER_THS=0,nofallback).
ENVIRONMENT VARIABLES
GC_DONT_GC
Turns off the garbage collection in Mono. This should be only used for debugging purposes
HTTP_PROXY
(Also http_proxy) If set, web requests using the Mono Class Library will be automatically proxied
through the given URL. Not supported on Windows, Mac OS, iOS or Android. See also NO_PROXY.
LLVM_COUNT
When Mono is compiled with LLVM support, this instructs the runtime to stop using LLVM after the
specified number of methods are JITed. This is a tool used in diagnostics to help isolate
problems in the code generation backend. For example LLVM_COUNT=10 would only compile 10 methods
with LLVM and then switch to the Mono JIT engine. LLVM_COUNT=0 would disable the LLVM engine
altogether.
MONO_AOT_CACHE
If set, this variable will instruct Mono to ahead-of-time compile new assemblies on demand and
store the result into a cache in ~/.mono/aot-cache.
MONO_ASPNET_INHIBIT_SETTINGSMAP
Mono contains a feature which allows modifying settings in the .config files shipped with Mono by
using config section mappers. The mappers and the mapping rules are defined in the
$prefix/etc/mono/2.0/settings.map file and, optionally, in the settings.map file found in the top-
level directory of your ASP.NET application. Both files are read by System.Web on application
startup, if they are found at the above locations. If you don't want the mapping to be performed
you can set this variable in your environment before starting the application and no action will
be taken.
MONO_ASPNET_WEBCONFIG_CACHESIZE
Mono has a cache of ConfigSection objects for speeding up WebConfigurationManager queries. Its
default size is 100 items, and when more items are needed, cache evictions start happening. If
evictions are too frequent this could impose unnecessary overhead, which could be avoided by using
this environment variable to set up a higher cache size (or to lower memory requirements by
decreasing it).
MONO_CAIRO_DEBUG_DISPOSE
If set, causes Mono.Cairo to collect stack traces when objects are allocated, so that the
finalization/Dispose warnings include information about the instance's origin.
MONO_CFG_DIR
If set, this variable overrides the default system configuration directory ($PREFIX/etc). It's
used to locate machine.config file.
MONO_COM
Sets the style of COM interop. If the value of this variable is "MS" Mono will use string
marhsalling routines from the liboleaut32 for the BSTR type library, any other values will use the
mono-builtin BSTR string marshalling.
MONO_CONFIG
If set, this variable overrides the default runtime configuration file ($PREFIX/etc/mono/config).
The --config command line options overrides the environment variable.
MONO_CPU_ARCH
Override the automatic cpu detection mechanism. Currently used only on arm. The format of the
value is as follows:
"armvV [thumb[2]]"
where V is the architecture number 4, 5, 6, 7 and the options can be currently be "thumb" or
"thumb2". Example:
MONO_CPU_ARCH="armv4 thumb" mono ...
MONO_ARM_FORCE_SOFT_FLOAT
When Mono is built with a soft float fallback on ARM and this variable is set to "1", Mono will
always emit soft float code, even if a VFP unit is detected.
MONO_DARWIN_WATCHER_MAXFDS
This is a debugging aid used to force limits on the FileSystemWatcher implementation in Darwin.
There is no limit by default.
MONO_DISABLE_AIO
If set, tells mono NOT to attempt using native asynchronous I/O services. In that case, a default
select/poll implementation is used. Currently only epoll() is supported.
MONO_DISABLE_MANAGED_COLLATION
If this environment variable is `yes', the runtime uses unmanaged collation (which actually means
no culture-sensitive collation). It internally disables managed collation functionality invoked
via the members of System.Globalization.CompareInfo class. Collation is enabled by default.
MONO_DISABLE_SHM
Unix only: If set, disables the shared memory files used for cross-process handles: process have
only private handles. This means that process and thread handles are not available to other
processes, and named mutexes, named events and named semaphores are not visible between processes.
This is can also be enabled by default by passing the "--disable-shared-handles" option to
configure. This is the default from mono 2.8 onwards.
MONO_DISABLE_SHARED_AREA
Unix only: If set, disable usage of shared memory for exposing performance counters. This means it
will not be possible to both externally read performance counters from this processes or read
those of external processes.
MONO_DNS
When set, enables the use of a fully managed DNS resolver instead of the regular libc functions.
This resolver performs much better when multiple queries are run in parallel.
Note that /etc/nsswitch.conf will be ignored.
MONO_EGD_SOCKET
For platforms that do not otherwise have a way of obtaining random bytes this can be set to the
name of a file system socket on which an egd or prngd daemon is listening.
MONO_ENABLE_COOP
This makes the Mono runtime and the SGen garbage collector run in cooperative mode as opposed to
run on preemptive mode. Preemptive mode is the mode that Mono has used historically, going back
to the Boehm days, where the garbage collector would run at any point and suspend execution of all
threads as required to perform a garbage collection. The cooperative mode on the other hand
requires the cooperation of all threads to stop at a safe point. This makes for an easier to
debug garbage collector. As of Mono 4.3.0 it is a work in progress, and while it works, it has
not been used extensively. This option enabled the feature and allows us to find spots that need
to be tuned for this mode of operation. Alternatively, this mode can be enabled at compile time
by using the --with-cooperative-gc flag when calling configure.
MONO_ENV_OPTIONS
This environment variable allows you to pass command line arguments to a Mono process through the
environment. This is useful for example to force all of your Mono processes to use LLVM or SGEN
without having to modify any launch scripts.
MONO_ENV_OPTIONS
Used to pass extra options to the debugger agent in the runtime, as they were passed using
--debugger-agent=.
MONO_EVENTLOG_TYPE
Sets the type of event log provider to use (for System.Diagnostics.EventLog). Possible values
are:
local[:path]
Persists event logs and entries to the local file system. The directory in which to
persist the event logs, event sources and entries can be specified as part of the value.
If the path is not explicitly set, it defaults to "/var/lib/mono/eventlog" on unix and
"%APPDATA%no\ventlog" on Windows.
win32 Uses the native win32 API to write events and registers event logs and event sources in the
registry. This is only available on Windows. On Unix, the directory permission for
individual event log and event source directories is set to 777 (with +t bit) allowing
everyone to read and write event log entries while only allowing entries to be deleted by
the user(s) that created them.
null Silently discards any events.
The default is "null" on Unix (and versions of Windows before NT), and "win32" on Windows NT (and
higher).
MONO_EXTERNAL_ENCODINGS
If set, contains a colon-separated list of text encodings to try when turning externally-generated
text (e.g. command-line arguments or filenames) into Unicode. The encoding names come from the
list provided by iconv, and the special case "default_locale" which refers to the current locale's
default encoding.
When reading externally-generated text strings UTF-8 is tried first, and then this list is tried
in order with the first successful conversion ending the search. When writing external text (e.g.
new filenames or arguments to new processes) the first item in this list is used, or UTF-8 if the
environment variable is not set.
The problem with using MONO_EXTERNAL_ENCODINGS to process your files is that it results in a
problem: although its possible to get the right file name it is not necessarily possible to open
the file. In general if you have problems with encodings in your filenames you should use the
"convmv" program.
MONO_GC_PARAMS
When using Mono with the SGen garbage collector this variable controls several parameters of the
collector. The variable's value is a comma separated list of words.
max-heap-size=size
Sets the maximum size of the heap. The size is specified in bytes and must be a power of
two. The suffixes `k', `m' and `g' can be used to specify kilo-, mega- and gigabytes,
respectively. The limit is the sum of the nursery, major heap and large object heap. Once
the limit is reached the application will receive OutOfMemoryExceptions when trying to
allocate. Not the full extent of memory set in max-heap-size could be available to satisfy
a single allocation due to internal fragmentation. By default heap limits is disabled and
the GC will try to use all available memory.
nursery-size=size
Sets the size of the nursery. The size is specified in bytes and must be a power of two.
The suffixes `k', `m' and `g' can be used to specify kilo-, mega- and gigabytes,
respectively. The nursery is the first generation (of two). A larger nursery will usually
speed up the program but will obviously use more memory. The default nursery size 4 MB.
major=collector Specifies which major collector to use.
Options are `marksweep' for the Mark&Sweep collector, and `marksweep-conc' for concurrent
Mark&Sweep. The non-concurrent Mark&Sweep collector is the default.
soft-heap-limit=size
Once the heap size gets larger than this size, ignore what the default major collection
trigger metric says and only allow four nursery size's of major heap growth between major
collections.
evacuation-threshold=threshold
Sets the evacuation threshold in percent. This option is only available on the Mark&Sweep
major collectors. The value must be an integer in the range 0 to 100. The default is 66.
If the sweep phase of the collection finds that the occupancy of a specific heap block type
is less than this percentage, it will do a copying collection for that block type in the
next major collection, thereby restoring occupancy to close to 100 percent. A value of 0
turns evacuation off.
(no-)lazy-sweep
Enables or disables lazy sweep for the Mark&Sweep collector. If enabled, the sweeping of
individual major heap blocks is done piecemeal whenever the need arises, typically during
nursery collections. Lazy sweeping is enabled by default.
(no-)concurrent-sweep
Enables or disables concurrent sweep for the Mark&Sweep collector. If enabled, the
iteration of all major blocks to determine which ones can be freed and which ones have to
be kept and swept, is done concurrently with the running program. Concurrent sweeping is
enabled by default.
stack-mark=mark-mode
Specifies how application threads should be scanned. Options are `precise` and
`conservative`. Precise marking allow the collector to know what values on stack are
references and what are not. Conservative marking threats all values as potentially
references and leave them untouched. Precise marking reduces floating garbage and can speed
up nursery collection and allocation rate, it has the downside of requiring a significant
extra memory per compiled method. The right option, unfortunately, requires
experimentation.
save-target-ratio=ratio
Specifies the target save ratio for the major collector. The collector lets a given amount
of memory to be promoted from the nursery due to minor collections before it triggers a
major collection. This amount is based on how much memory it expects to free. It is
represented as a ratio of the size of the heap after a major collection. Valid values are
between 0.1 and 2.0. The default is 0.5. Smaller values will keep the major heap size
smaller but will trigger more major collections. Likewise, bigger values will use more
memory and result in less frequent major collections. This option is EXPERIMENTAL, so it
might disappear in later versions of mono.
default-allowance-ratio=ratio
Specifies the default allocation allowance when the calculated size is too small. The
allocation allowance is how much memory the collector let be promoted before triggered a
major collection. It is a ratio of the nursery size. Valid values are between 1.0 and
10.0. The default is 4.0. Smaller values lead to smaller heaps and more frequent major
collections. Likewise, bigger values will allow the heap to grow faster but use more
memory when it reaches a stable size. This option is EXPERIMENTAL, so it might disappear
in later versions of mono.
minor=minor-collector
Specifies which minor collector to use. Options are 'simple' which promotes all objects
from the nursery directly to the old generation and 'split' which lets object stay longer
on the nursery before promoting.
alloc-ratio=ratio
Specifies the ratio of memory from the nursery to be use by the alloc space. This only can
only be used with the split minor collector. Valid values are integers between 1 and 100.
Default is 60.
promotion-age=age
Specifies the required age of an object must reach inside the nursery before been promoted
to the old generation. This only can only be used with the split minor collector. Valid
values are integers between 1 and 14. Default is 2.
(no-)cementing
Enables or disables cementing. This can dramatically shorten nursery collection times on
some benchmarks where pinned objects are referred to from the major heap.
allow-synchronous-major
This forbids the major collector from performing synchronous major collections. The major
collector might want to do a synchronous collection due to excessive fragmentation.
Disabling this might trigger OutOfMemory error in situations that would otherwise not
happen.
MONO_GC_DEBUG
When using Mono with the SGen garbage collector this environment variable can be used to turn on
various debugging features of the collector. The value of this variable is a comma separated list
of words. Do not use these options in production.
number Sets the debug level to the specified number.
print-allowance
After each major collection prints memory consumption for before and after the collection
and the allowance for the minor collector, i.e. how much the heap is allowed to grow from
minor collections before the next major collection is triggered.
print-pinning
Gathers statistics on the classes whose objects are pinned in the nursery and for which
global remset entries are added. Prints those statistics when shutting down.
collect-before-allocs
check-at-minor-collections
This performs a consistency check on minor collections and also clears the nursery at
collection time, instead of the default, when buffers are allocated (clear-at-gc). The
consistency check ensures that there are no major to minor references that are not on the
remembered sets.
mod-union-consistency-check
Checks that the mod-union cardtable is consistent before each finishing major collection
pause. This check is only applicable to concurrent major collectors.
check-mark-bits
Checks that mark bits in the major heap are consistent at the end of each major collection.
Consistent mark bits mean that if an object is marked, all objects that it had references
to must also be marked.
check-nursery-pinned
After nursery collections, and before starting concurrent collections, check whether all
nursery objects are pinned, or not pinned - depending on context. Does nothing when the
split nursery collector is used.
xdomain-checks
Performs a check to make sure that no references are left to an unloaded AppDomain.
clear-at-tlab-creation
Clears the nursery incrementally when the thread local allocation buffers (TLAB) are
created. The default setting clears the whole nursery at GC time.
debug-clear-at-tlab-creation
Clears the nursery incrementally when the thread local allocation buffers (TLAB) are
created, but at GC time fills it with the byte `0xff`, which should result in a crash more
quickly if `clear-at-tlab-creation` doesn't work properly.
clear-at-gc
This clears the nursery at GC time instead of doing it when the thread local allocation
buffer (TLAB) is created. The default is to clear the nursery at TLAB creation time.
disable-minor
Don't do minor collections. If the nursery is full, a major collection is triggered
instead, unless it, too, is disabled.
disable-major
Don't do major collections.
conservative-stack-mark
Forces the GC to scan the stack conservatively, even if precise scanning is available.
no-managed-allocator
Disables the managed allocator.
check-scan-starts
If set, does a plausibility check on the scan_starts before and after each collection
verify-nursery-at-minor-gc
If set, does a complete object walk of the nursery at the start of each minor collection.
dump-nursery-at-minor-gc
If set, dumps the contents of the nursery at the start of each minor collection. Requires
verify-nursery-at-minor-gc to be set.
heap-dump=file
Dumps the heap contents to the specified file. To visualize the information, use the
mono-heapviz tool.
binary-protocol=file
Outputs the debugging output to the specified file. For this to work, Mono needs to be
compiled with the BINARY_PROTOCOL define on sgen-gc.c. You can then use this command to
explore the output
sgen-grep-binprot 0x1234 0x5678 < file
nursery-canaries
If set, objects allocated in the nursery are suffixed with a canary (guard) word, which is
checked on each minor collection. Can be used to detect/debug heap corruption issues.
do-not-finalize(=classes)
If enabled, finalizers will not be run. Everything else will be unaffected: finalizable
objects will still be put into the finalization queue where they survive until they're
scheduled to finalize. Once they're not in the queue anymore they will be collected
regularly. If a list of comma-separated class names is given, only objects from those
classes will not be finalized.
log-finalizers
Log verbosely around the finalization process to aid debugging.
MONO_GAC_PREFIX
Provides a prefix the runtime uses to look for Global Assembly Caches. Directories are separated
by the platform path separator (colons on unix). MONO_GAC_PREFIX should point to the top directory
of a prefixed install. Or to the directory provided in the gacutil /gacdir command. Example:
/home/username/.mono:/usr/local/mono/
MONO_IOMAP
Enables some filename rewriting support to assist badly-written applications that hard-code
Windows paths. Set to a colon-separated list of "drive" to strip drive letters, or "case" to do
case-insensitive file matching in every directory in a path. "all" enables all rewriting methods.
(Backslashes are always mapped to slashes if this variable is set to a valid option).
For example, this would work from the shell:
MONO_IOMAP=drive:case
export MONO_IOMAP
If you are using mod_mono to host your web applications, you can use the MonoIOMAP directive
instead, like this:
MonoIOMAP <appalias> all
See mod_mono(8) for more details.
Additionally. Mono includes a profiler module which allows one to track what adjustements to file
paths IOMAP code needs to do. The tracking code reports the managed location (full stack trace)
from which the IOMAP-ed call was made and, on process exit, the locations where all the IOMAP-ed
strings were created in managed code. The latter report is only approximate as it is not always
possible to estimate the actual location where the string was created. The code uses simple
heuristics - it analyzes stack trace leading back to the string allocation location and ignores
all the managed code which lives in assemblies installed in GAC as well as in the class libraries
shipped with Mono (since they are assumed to be free of case-sensitivity issues). It then reports
the first location in the user's code - in most cases this will be the place where the string is
allocated or very close to the location. The reporting code is implemented as a custom profiler
module (see the "PROFILING" section) and can be loaded in the following way:
mono --profile=iomap yourapplication.exe
Note, however, that Mono currently supports only one profiler module at a time.
MONO_LLVM
When Mono is using the LLVM code generation backend you can use this environment variable to pass
code generation options to the LLVM compiler.
MONO_MANAGED_WATCHER
If set to "disabled", System.IO.FileSystemWatcher will use a file watcher implementation which
silently ignores all the watching requests. If set to any other value,
System.IO.FileSystemWatcher will use the default managed implementation (slow). If unset, mono
will try to use inotify, FAM, Gamin, kevent under Unix systems and native API calls on Windows,
falling back to the managed implementation on error.
MONO_MESSAGING_PROVIDER
Mono supports a plugin model for its implementation of System.Messaging making it possible to
support a variety of messaging implementations (e.g. AMQP, ActiveMQ). To specify which messaging
implementation is to be used the evironement variable needs to be set to the full class name for
the provider. E.g. to use the RabbitMQ based AMQP implementation the variable should be set to:
Mono.Messaging.RabbitMQ.RabbitMQMessagingProvider,Mono.Messaging.RabbitMQ
MONO_NO_SMP
If set causes the mono process to be bound to a single processor. This may be
useful when debugging or working around race conditions.
MONO_NO_TLS
Disable inlining of thread local accesses. Try setting this if you get a segfault
early on in the execution of mono.
MONO_PATH
Provides a search path to the runtime where to look for library
files. This is a tool convenient for debugging applications, but
should not be used by deployed applications as it breaks the assembly
loader in subtle ways.
Directories are separated by the platform path separator (colons on unix). Example:
/home/username/lib:/usr/local/mono/lib
Relative paths are resolved based on the launch-time current directory.
Alternative solutions to MONO_PATH include: installing libraries into
the Global Assembly Cache (see gacutil(1)) or having the dependent
libraries side-by-side with the main executable.
For a complete description of recommended practices for application
deployment, see
http://www.mono-project.com/docs/getting-started/application-deployment/
MONO_SHARED_DIR
If set its the directory where the ".wapi" handle state is stored.
This is the directory where the Windows I/O Emulation layer stores its
shared state data (files, events, mutexes, pipes). By default Mono
will store the ".wapi" directory in the users's home directory.
MONO_SHARED_HOSTNAME
Uses the string value of this variable as a replacement for the host name when
creating file names in the ".wapi" directory. This helps if the host name of
your machine is likely to be changed when a mono application is running or if
you have a .wapi directory shared among several different computers.
Mono typically uses the hostname to create the files that are used to
share state across multiple Mono processes. This is done to support
home directories that might be shared over the network.
MONO_STRICT_IO_EMULATION
If set, extra checks are made during IO operations. Currently, this
includes only advisory locks around file writes.
MONO_THEME
The name of the theme to be used by Windows.Forms. Available themes today
include "clearlooks", "nice" and "win32".
The default is "win32".
MONO_TLS_SESSION_CACHE_TIMEOUT
The time, in seconds, that the SSL/TLS session cache will keep it's entry to
avoid a new negotiation between the client and a server. Negotiation are very
CPU intensive so an application-specific custom value may prove useful for
small embedded systems.
The default is 180 seconds.
MONO_THREADS_PER_CPU
The minimum number of threads in the general threadpool will be
MONO_THREADS_PER_CPU * number of CPUs. The default value for this
variable is 1.
MONO_XMLSERIALIZER_THS
Controls the threshold for the XmlSerializer to produce a custom
serializer for a given class instead of using the Reflection-based
interpreter. The possible values are `no' to disable the use of a
custom serializer or a number to indicate when the XmlSerializer
should start serializing. The default value is 50, which means that
the a custom serializer will be produced on the 50th use.
MONO_X509_REVOCATION_MODE
Sets the revocation mode used when validating a X509 certificate chain (https,
ftps, smtps...). The default is 'nocheck', which performs no revocation check
at all. The other possible values are 'offline', which performs CRL check (not
implemented yet) and 'online' which uses OCSP and CRL to verify the revocation
status (not implemented yet).
NO_PROXY
(Also no_proxy) If both HTTP_PROXY and NO_PROXY are
set, NO_PROXY will be treated as a comma-separated list of "bypass" domains
which will not be sent through the proxy. Domains in NO_PROXY may contain
wildcards, as in "*.mono-project.com" or "build????.local". Not supported on
Windows, Mac OS, iOS or Android.
ENVIRONMENT VARIABLES FOR DEBUGGING
MONO_ASPNET_NODELETE
If set to any value, temporary source files generated by ASP.NET support classes will not be
removed. They will be kept in the user's temporary directory.
MONO_DEBUG
If set, enables some features of the runtime useful for debugging. This variable should contain a
comma separated list of debugging options. Currently, the following options are supported:
align-small-structs
Enables small structs alignment to 4/8 bytes.
arm-use-fallback-tls
When this option is set on ARM, a fallback TLS will be used instead of the default fast
TLS.
break-on-unverified
If this variable is set, when the Mono VM runs into a verification problem, instead of
throwing an exception it will break into the debugger. This is useful when debugging
verifier problems
casts This option can be used to get more detailed information from InvalidCast exceptions, it
will provide information about the types involved.
check-pinvoke-callconv
This option causes the runtime to check for calling convention mismatches when using
pinvoke, i.e. mixing cdecl/stdcall. It only works on windows. If a mismatch is detected, an
ExecutionEngineException is thrown.
collect-pagefault-stats
Collects information about pagefaults. This is used internally to track the number of
page faults produced to load metadata. To display this information you must use this
option with "--stats" command line option.
debug-domain-unload
When this option is set, the runtime will invalidate the domain memory pool instead of
destroying it.
disable_omit_fp
Disables a compiler optimization where the frame pointer is omitted from the stack. This
optimization can interact badly with debuggers.
dont-free-domains
This is an Optimization for multi-AppDomain applications (most commonly ASP.NET
applications). Due to internal limitations Mono, Mono by default does not use typed
allocations on multi-appDomain applications as they could leak memory when a domain is
unloaded. Although this is a fine default, for applications that use more than on
AppDomain heavily (for example, ASP.NET applications) it is worth trading off the small
leaks for the increased performance (additionally, since ASP.NET applications are not
likely going to unload the application domains on production systems, it is worth using
this feature).
dyn-runtime-invoke
Instructs the runtime to try to use a generic runtime-invoke wrapper instead of creating
one invoke wrapper.
explicit-null-checks
Makes the JIT generate an explicit NULL check on variable dereferences instead of depending
on the operating system to raise a SIGSEGV or another form of trap event when an invalid
memory location is accessed.
gdb Equivalent to setting the MONO_XDEBUG variable, this emits symbols into a shared library as
the code is JITed that can be loaded into GDB to inspect symbols.
gen-seq-points
Automatically generates sequence points where the IL stack is empty. These are places
where the debugger can set a breakpoint.
no-compact-seq-points
Unless the option is used, the runtime generates sequence points data that maps native
offsets to IL offsets. Sequence point data is used to display IL offset in stacktraces.
Stacktraces with IL offsets can be symbolicated using mono-symbolicate tool.
handle-sigint
Captures the interrupt signal (Control-C) and displays a stack trace when pressed. Useful
to find out where the program is executing at a given point. This only displays the stack
trace of a single thread.
init-stacks
Instructs the runtime to initialize the stack with some known values (0x2a on x86-64) at
the start of a method to assist in debuggin the JIT engine.
keep-delegates
This option will leak delegate trampolines that are no longer referenced as to present the
user with more information about a delegate misuse. Basically a delegate instance might be
created, passed to unmanaged code, and no references kept in managed code, which will
garbage collect the code. With this option it is possible to track down the source of the
problems.
no-gdb-backtrace
This option will disable the GDB backtrace emitted by the runtime after a SIGSEGV or
SIGABRT in unmanaged code.
partial-sharing
When this option is set, the runtime can share generated code between generic types
effectively reducing the amount of code generated.
reverse-pinvoke-exceptions
This option will cause mono to abort with a descriptive message when during stack unwinding
after an exception it reaches a native stack frame. This happens when a managed delegate is
passed to native code, and the managed delegate throws an exception. Mono will normally try
to unwind the stack to the first (managed) exception handler, and it will skip any native
stack frames in the process. This leads to undefined behaviour (since mono doesn't know how
to process native frames), leaks, and possibly crashes too.
single-imm-size
This guarantees that each time managed code is compiled the same instructions and registers
are used, regardless of the size of used values.
soft-breakpoints
This option allows using single-steps and breakpoints in hardware where we cannot do it
with signals.
suspend-on-sigsegv
This option will suspend the program when a native SIGSEGV is received. This is useful for
debugging crashes which do not happen under gdb, since a live process contains more
information than a core file.
suspend-on-exception
This option will suspend the program when an exception occurs.
suspend-on-unhandled
This option will suspend the program when an unhandled exception occurs.
MONO_LOG_LEVEL
The logging level, possible values are `error', `critical', `warning', `message', `info' and
`debug'. See the DEBUGGING section for more details.
MONO_LOG_MASK
Controls the domain of the Mono runtime that logging will apply to. If set, the log mask is
changed to the set value. Possible values are "asm" (assembly loader), "type", "dll" (native
library loader), "gc" (garbage collector), "cfg" (config file loader), "aot" (precompiler),
"security" (e.g. Moonlight CoreCLR support) and "all". The default value is "all". Changing the
mask value allows you to display only messages for a certain component. You can use multiple masks
by comma separating them. For example to see config file messages and assembly loader messages set
you mask to "asm,cfg".
MONO_TRACE
Used for runtime tracing of method calls. The format of the comma separated trace options is:
[-]M:method name
[-]N:namespace
[-]T:class name
[-]all
[-]program
disabled Trace output off upon start.
You can toggle trace output on/off sending a SIGUSR2 signal to the program.
MONO_TRACE_LISTENER
If set, enables the System.Diagnostics.DefaultTraceListener, which will print the output of the
System.Diagnostics Trace and Debug classes. It can be set to a filename, and to Console.Out or
Console.Error to display output to standard output or standard error, respectively. If it's set to
Console.Out or Console.Error you can append an optional prefix that will be used when writing
messages like this: Console.Error:MyProgramName. See the System.Diagnostics.DefaultTraceListener
documentation for more information.
MONO_WCF_TRACE
This eases WCF diagnostics functionality by simply outputs all log messages from WCF engine to
"stdout", "stderr" or any file passed to this environment variable. The log format is the same as
usual diagnostic output.
MONO_XEXCEPTIONS
This throws an exception when a X11 error is encountered; by default a message is displayed but
execution continues
MONO_XMLSERIALIZER_DEBUG
Set this value to 1 to prevent the serializer from removing the temporary files that are created
for fast serialization; This might be useful when debugging.
MONO_XSYNC
This is used in the System.Windows.Forms implementation when running with the X11 backend. This
is used to debug problems in Windows.Forms as it forces all of the commands send to X11 server to
be done synchronously. The default mode of operation is asynchronous which makes it hard to
isolate the root of certain problems.
MONO_XDEBUG
When the the MONO_XDEBUG env var is set, debugging info for JITted code is emitted into a shared
library, loadable into gdb. This enables, for example, to see managed frame names on gdb
backtraces.
MONO_VERBOSE_METHOD
Enables the maximum JIT verbosity for the specified method. This is very helpfull to diagnose a
miscompilation problems of a specific method.
MONO_JIT_DUMP_METHOD
Enables sending of the JITs intermediate representation for a specified method to the
IdealGraphVisualizer tool.
MONO_VERBOSE_HWCAP
If set, makes the JIT output information about detected CPU features (such as SSE, CMOV, FCMOV,
etc) to stdout.
MONO_CONSERVATIVE_HWCAP
If set, the JIT will not perform any hardware capability detection. This may be useful to pinpoint
the cause of JIT issues. This is the default when Mono is built as an AOT cross compiler, so that
the generated code will run on most hardware.
VALGRIND
If you want to use Valgrind, you will find the file `mono.supp' useful, it contains the suppressions for
the GC which trigger incorrect warnings. Use it like this:
valgrind --suppressions=mono.supp mono ...
DTRACE
On some platforms, Mono can expose a set of DTrace probes (also known as user-land statically defined,
USDT Probes).
They are defined in the file `mono.d'.
ves-init-begin, ves-init-end
Begin and end of runtime initialization.
method-compile-begin, method-compile-end
Begin and end of method compilation. The probe arguments are class name, method name and
signature, and in case of method-compile-end success or failure of compilation.
gc-begin, gc-end
Begin and end of Garbage Collection.
To verify the availability of the probes, run:
dtrace -P mono'$target' -l -c mono
PERMISSIONS
Mono's Ping implementation for detecting network reachability can create the ICMP packets itself without
requiring the system ping command to do the work. If you want to enable this on Linux for non-root
users, you need to give the Mono binary special permissions.
As root, run this command:
# setcap cap_net_raw=+ep /usr/bin/mono
FILES
On Unix assemblies are loaded from the installation lib directory. If you set `prefix' to /usr, the
assemblies will be located in /usr/lib. On Windows, the assemblies are loaded from the directory where
mono and mint live.
~/.mono/aot-cache
The directory for the ahead-of-time compiler demand creation assemblies are located.
/etc/mono/config, ~/.mono/config
Mono runtime configuration file. See the mono-config(5) manual page for more information.
~/.config/.mono/certs, /usr/share/.mono/certs
Contains Mono certificate stores for users / machine. See the certmgr(1) manual page for more
information on managing certificate stores and the mozroots(1) page for information on how to
import the Mozilla root certificates into the Mono certificate store.
~/.mono/assemblies/ASSEMBLY/ASSEMBLY.config
Files in this directory allow a user to customize the configuration for a given system assembly,
the format is the one described in the mono-config(5) page.
~/.config/.mono/keypairs, /usr/share/.mono/keypairs
Contains Mono cryptographic keypairs for users / machine. They can be accessed by using a
CspParameters object with DSACryptoServiceProvider and RSACryptoServiceProvider classes.
~/.config/.isolatedstorage, ~/.local/share/.isolatedstorage, /usr/share/.isolatedstorage
Contains Mono isolated storage for non-roaming users, roaming users and local machine. Isolated
storage can be accessed using the classes from the System.IO.IsolatedStorage namespace.
<assembly>.config
Configuration information for individual assemblies is loaded by the runtime from side-by-side
files with the .config files, see the http://www.mono-project.com/Config for more information.
Web.config, web.config
ASP.NET applications are configured through these files, the configuration is done on a per-
directory basis. For more information on this subject see the http://www.mono-
project.com/Config_system.web page.
MAILING LISTS
Mailing lists are listed at the http://www.mono-project.com/community/help/mailing-lists/
WEB SITE
http://www.mono-project.com
SEE ALSO
certmgr(1), csharp(1), mcs(1), mdb(1), monocov(1), monodis(1), mono-config(5), mozroots(1), mprof-
report(1), pdb2mdb(1), xsp(1), mod_mono(8).
For more information on AOT: http://www.mono-project.com/docs/advanced/aot/
For ASP.NET-related documentation, see the xsp(1) manual page
Mono(Mono 3.0)