Provided by: gcc-8_8.4.0-1ubuntu1~18.04_amd64 bug

NAME

       gcov - coverage testing tool

SYNOPSIS

       gcov [-v|--version] [-h|--help]
            [-a|--all-blocks]
            [-b|--branch-probabilities]
            [-c|--branch-counts]
            [-d|--display-progress]
            [-f|--function-summaries]
            [-i|--intermediate-format]
            [-j|--human-readable]
            [-k|--use-colors]
            [-l|--long-file-names]
            [-m|--demangled-names]
            [-n|--no-output]
            [-o|--object-directory directory|file]
            [-p|--preserve-paths]
            [-r|--relative-only]
            [-s|--source-prefix directory]
            [-u|--unconditional-branches]
            [-x|--hash-filenames]
            files

DESCRIPTION

       gcov is a test coverage program.  Use it in concert with GCC to analyze your programs to help create more
       efficient, faster running code and to discover untested parts of your program.  You can use gcov as a
       profiling tool to help discover where your optimization efforts will best affect your code.  You can also
       use gcov along with the other profiling tool, gprof, to assess which parts of your code use the greatest
       amount of computing time.

       Profiling tools help you analyze your code's performance.  Using a profiler such as gcov or gprof, you
       can find out some basic performance statistics, such as:

       *   how often each line of code executes

       *   what lines of code are actually executed

       *   how much computing time each section of code uses

       Once  you  know  these things about how your code works when compiled, you can look at each module to see
       which modules should be optimized.  gcov helps you determine where to work on optimization.

       Software developers also use coverage testing in concert  with  testsuites,  to  make  sure  software  is
       actually  good  enough for a release.  Testsuites can verify that a program works as expected; a coverage
       program tests to see how much of the  program  is  exercised  by  the  testsuite.   Developers  can  then
       determine what kinds of test cases need to be added to the testsuites to create both better testing and a
       better final product.

       You  should  compile  your code without optimization if you plan to use gcov because the optimization, by
       combining some lines of code into one function, may not give you as much information as you need to  look
       for  `hot  spots'  where  the  code  is  using  a  great  deal  of computer time.  Likewise, because gcov
       accumulates statistics by line (at the lowest resolution), it works best with a  programming  style  that
       places  only  one statement on each line.  If you use complicated macros that expand to loops or to other
       control structures, the statistics are less helpful---they only report on the line where the  macro  call
       appears.   If  your  complex  macros behave like functions, you can replace them with inline functions to
       solve this problem.

       gcov creates a logfile called sourcefile.gcov which indicates how many times each line of a  source  file
       sourcefile.c  has  executed.   You  can  use  these  logfiles  along with gprof to aid in fine-tuning the
       performance of your programs.  gprof gives timing information you can use along with the information  you
       get from gcov.

       gcov  works  only  on  code  compiled  with  GCC.   It is not compatible with any other profiling or test
       coverage mechanism.

OPTIONS

       -a
       --all-blocks
           Write individual execution counts for every basic block.  Normally gcov outputs execution counts only
           for the main blocks of a line.  With this option you can determine if blocks within a single line are
           not being executed.

       -b
       --branch-probabilities
           Write branch frequencies to the output file, and write branch summary info to  the  standard  output.
           This  option  allows  you  to  see  how  often  each branch in your program was taken.  Unconditional
           branches will not be shown, unless the -u option is given.

       -c
       --branch-counts
           Write branch frequencies as the number of branches taken, rather  than  the  percentage  of  branches
           taken.

       -d
       --display-progress
           Display the progress on the standard output.

       -f
       --function-summaries
           Output summaries for each function in addition to the file level summary.

       -h
       --help
           Display  help  about  using  gcov  (on  the  standard  output),  and  exit  without doing any further
           processing.

       -i
       --intermediate-format
           Output gcov file in an easy-to-parse intermediate text format that can  be  used  by  lcov  or  other
           tools. The output is a single .gcov file per .gcda file. No source code is required.

           The format of the intermediate .gcov file is plain text with one entry per line

                   version:<gcc_version>
                   file:<source_file_name>
                   function:<start_line_number>,<end_line_number>,<execution_count>,<function_name>
                   lcount:<line number>,<execution_count>,<has_unexecuted_block>
                   branch:<line_number>,<branch_coverage_type>

                   Where the <branch_coverage_type> is
                      notexec (Branch not executed)
                      taken (Branch executed and taken)
                      nottaken (Branch executed, but not taken)

           There can be multiple file entries in an intermediate gcov file. All entries following a file pertain
           to  that  source  file  until  the  next file entry.  If there are multiple functions that start on a
           single line, then corresponding lcount is repeated multiple times.

           Here is a sample when -i is used in conjunction with -b option:

                   version: 8.1.0 20180103
                   file:tmp.cpp
                   function:7,7,0,_ZN3FooIcEC2Ev
                   function:7,7,1,_ZN3FooIiEC2Ev
                   function:8,8,0,_ZN3FooIcE3incEv
                   function:8,8,2,_ZN3FooIiE3incEv
                   function:18,37,1,main
                   lcount:7,0,1
                   lcount:7,1,0
                   lcount:8,0,1
                   lcount:8,2,0
                   lcount:18,1,0
                   lcount:21,1,0
                   branch:21,taken
                   branch:21,nottaken
                   lcount:23,1,0
                   branch:23,taken
                   branch:23,nottaken
                   lcount:24,1,0
                   branch:24,taken
                   branch:24,nottaken
                   lcount:25,1,0
                   lcount:27,11,0
                   branch:27,taken
                   branch:27,taken
                   lcount:28,10,0
                   lcount:30,1,1
                   branch:30,nottaken
                   branch:30,taken
                   lcount:32,1,0
                   branch:32,nottaken
                   branch:32,taken
                   lcount:33,0,1
                   branch:33,notexec
                   branch:33,notexec
                   lcount:35,1,0
                   branch:35,taken
                   branch:35,nottaken
                   lcount:36,1,0

       -j
       --human-readable
           Write counts in human readable format (like 24k).

       -k
       --use-colors
           Use colors for lines of code that have zero coverage.  We use red color for non-exceptional lines and
           cyan for exceptional.  Same colors are used for basic blocks with -a option.

       -l
       --long-file-names
           Create long file names for included source files.  For example, if the header file x.h contains code,
           and was included in the file a.c, then running gcov on the file  a.c  will  produce  an  output  file
           called  a.c##x.h.gcov  instead of x.h.gcov.  This can be useful if x.h is included in multiple source
           files and you want to see the individual contributions.  If you use the -p option, both the including
           and included file names will be complete path names.

       -m
       --demangled-names
           Display demangled function names in output. The default is to show mangled function names.

       -n
       --no-output
           Do not create the gcov output file.

       -o directory|file
       --object-directory directory
       --object-file file
           Specify either the directory containing the gcov data files, or the object path name.  The .gcno, and
           .gcda data files are searched for using this option.  If a directory is specified, the data files are
           in that directory and named after the input file name, without its extension.  If a file is specified
           here, the data files are named after that file, without its extension.

       -p
       --preserve-paths
           Preserve complete path information in the names of generated .gcov files.  Without this option,  just
           the  filename  component  is  used.   With  this  option, all directories are used, with / characters
           translated to # characters, . directory components removed and unremoveable ..  components renamed to
           ^.  This is useful if sourcefiles are in several different directories.

       -r
       --relative-only
           Only output information about source files with a relative pathname (after  source  prefix  elision).
           Absolute  paths  are  usually  system  header  files  and coverage of any inline functions therein is
           normally uninteresting.

       -s directory
       --source-prefix directory
           A prefix for source file names to remove when generating the output coverage files.  This  option  is
           useful  when building in a separate directory, and the pathname to the source directory is not wanted
           when determining the  output  file  names.   Note  that  this  prefix  detection  is  applied  before
           determining whether the source file is absolute.

       -u
       --unconditional-branches
           When branch probabilities are given, include those of unconditional branches.  Unconditional branches
           are normally not interesting.

       -v
       --version
           Display  the  gcov  version  number  (on  the  standard  output),  and exit without doing any further
           processing.

       -w
       --verbose
           Print verbose informations related to basic blocks and arcs.

       -x
       --hash-filenames
           By default, gcov uses the full pathname of the source files to create an output filename.   This  can
           lead  to  long  filenames that can overflow filesystem limits.  This option creates names of the form
           source-file##md5.gcov, where the source-file component  is  the  final  filename  part  and  the  md5
           component is calculated from the full mangled name that would have been used otherwise.

       gcov  should be run with the current directory the same as that when you invoked the compiler.  Otherwise
       it will not be able to locate the source files.  gcov  produces  files  called  mangledname.gcov  in  the
       current  directory.   These  contain the coverage information of the source file they correspond to.  One
       .gcov file is produced for each source (or header) file containing code, which was  compiled  to  produce
       the data files.  The mangledname part of the output file name is usually simply the source file name, but
       can be something more complicated if the -l or -p options are given.  Refer to those options for details.

       If  you  invoke  gcov  with  multiple  input  files,  the  contributions from each input file are summed.
       Typically you would invoke it with the same list of files as the final link of your executable.

       The .gcov files contain the : separated fields along with program source code.  The format is

               <execution_count>:<line_number>:<source line text>

       Additional block information may  succeed  each  line,  when  requested  by  command  line  option.   The
       execution_count is - for lines containing no code.  Unexecuted lines are marked ##### or =====, depending
       on  whether  they  are reachable by non-exceptional paths or only exceptional paths such as C++ exception
       handlers, respectively. Given -a option, unexecuted blocks  are  marked  $$$$$  or  %%%%%,  depending  on
       whether  a  basic  block  is  reachable  via non-exceptional or exceptional paths.  Executed basic blocks
       having a statement with zero execution_count end with * character and are colored with magenta color with
       -k option.  The functionality is not supported in Ada.

       Note that GCC can completely remove the bodies of functions that are not needed -- for instance  if  they
       are  inlined  everywhere.   Such  functions  are  marked  with  -,  which  can  be  confusing.   Use  the
       -fkeep-inline-functions and -fkeep-static-functions options to retain these functions and allow  gcov  to
       properly show their execution_count.

       Some lines of information at the start have line_number of zero.  These preamble lines are of the form

               -:0:<tag>:<value>

       The  ordering  and number of these preamble lines will be augmented as gcov development progresses --- do
       not rely on them remaining unchanged.  Use tag to locate a particular preamble line.

       The additional block information is of the form

               <tag> <information>

       The information is human readable, but designed to be simple enough for machine parsing too.

       When printing percentages, 0% and 100% are  only  printed  when  the  values  are  exactly  0%  and  100%
       respectively.   Other  values  which would conventionally be rounded to 0% or 100% are instead printed as
       the nearest non-boundary value.

       When using gcov, you must first compile  your  program  with  two  special  GCC  options:  -fprofile-arcs
       -ftest-coverage.   This tells the compiler to generate additional information needed by gcov (basically a
       flow graph of the program) and also includes additional code in the object files for generating the extra
       profiling information needed by gcov.  These additional files are  placed  in  the  directory  where  the
       object file is located.

       Running  the  program  will  cause  profile  output  to be generated.  For each source file compiled with
       -fprofile-arcs, an accompanying .gcda file will be placed in the object file directory.

       Running gcov with your program's source file names as arguments will now produce a listing  of  the  code
       along with frequency of execution for each line.  For example, if your program is called tmp.cpp, this is
       what you see when you use the basic gcov facility:

               $ g++ -fprofile-arcs -ftest-coverage tmp.cpp
               $ a.out
               $ gcov tmp.cpp -m
               File 'tmp.cpp'
               Lines executed:92.86% of 14
               Creating 'tmp.cpp.gcov'

       The file tmp.cpp.gcov contains output from gcov.  Here is a sample:

                       -:    0:Source:tmp.cpp
                       -:    0:Graph:tmp.gcno
                       -:    0:Data:tmp.gcda
                       -:    0:Runs:1
                       -:    0:Programs:1
                       -:    1:#include <stdio.h>
                       -:    2:
                       -:    3:template<class T>
                       -:    4:class Foo
                       -:    5:{
                       -:    6:  public:
                      1*:    7:  Foo(): b (1000) {}
               ------------------
               Foo<char>::Foo():
                   #####:    7:  Foo(): b (1000) {}
               ------------------
               Foo<int>::Foo():
                       1:    7:  Foo(): b (1000) {}
               ------------------
                      2*:    8:  void inc () { b++; }
               ------------------
               Foo<char>::inc():
                   #####:    8:  void inc () { b++; }
               ------------------
               Foo<int>::inc():
                       2:    8:  void inc () { b++; }
               ------------------
                       -:    9:
                       -:   10:  private:
                       -:   11:  int b;
                       -:   12:};
                       -:   13:
                       -:   14:template class Foo<int>;
                       -:   15:template class Foo<char>;
                       -:   16:
                       -:   17:int
                       1:   18:main (void)
                       -:   19:{
                       -:   20:  int i, total;
                       1:   21:  Foo<int> counter;
                       -:   22:
                       1:   23:  counter.inc();
                       1:   24:  counter.inc();
                       1:   25:  total = 0;
                       -:   26:
                      11:   27:  for (i = 0; i < 10; i++)
                      10:   28:    total += i;
                       -:   29:
                      1*:   30:  int v = total > 100 ? 1 : 2;
                       -:   31:
                       1:   32:  if (total != 45)
                   #####:   33:    printf ("Failure\n");
                       -:   34:  else
                       1:   35:    printf ("Success\n");
                       1:   36:  return 0;
                       -:   37:}

       Note  that  line  7  is  shown  in  the report multiple times.  First occurrence presents total number of
       execution of the line and the next two belong to instances of class Foo constructors.  As  you  can  also
       see, line 30 contains some unexecuted basic blocks and thus execution count has asterisk symbol.

       When you use the -a option, you will get individual block counts, and the output looks like this:

                       -:    0:Source:tmp.cpp
                       -:    0:Graph:tmp.gcno
                       -:    0:Data:tmp.gcda
                       -:    0:Runs:1
                       -:    0:Programs:1
                       -:    1:#include <stdio.h>
                       -:    2:
                       -:    3:template<class T>
                       -:    4:class Foo
                       -:    5:{
                       -:    6:  public:
                      1*:    7:  Foo(): b (1000) {}
               ------------------
               Foo<char>::Foo():
                   #####:    7:  Foo(): b (1000) {}
               ------------------
               Foo<int>::Foo():
                       1:    7:  Foo(): b (1000) {}
               ------------------
                      2*:    8:  void inc () { b++; }
               ------------------
               Foo<char>::inc():
                   #####:    8:  void inc () { b++; }
               ------------------
               Foo<int>::inc():
                       2:    8:  void inc () { b++; }
               ------------------
                       -:    9:
                       -:   10:  private:
                       -:   11:  int b;
                       -:   12:};
                       -:   13:
                       -:   14:template class Foo<int>;
                       -:   15:template class Foo<char>;
                       -:   16:
                       -:   17:int
                       1:   18:main (void)
                       -:   19:{
                       -:   20:  int i, total;
                       1:   21:  Foo<int> counter;
                       1:   21-block  0
                       -:   22:
                       1:   23:  counter.inc();
                       1:   23-block  0
                       1:   24:  counter.inc();
                       1:   24-block  0
                       1:   25:  total = 0;
                       -:   26:
                      11:   27:  for (i = 0; i < 10; i++)
                       1:   27-block  0
                      11:   27-block  1
                      10:   28:    total += i;
                      10:   28-block  0
                       -:   29:
                      1*:   30:  int v = total > 100 ? 1 : 2;
                       1:   30-block  0
                   %%%%%:   30-block  1
                       1:   30-block  2
                       -:   31:
                       1:   32:  if (total != 45)
                       1:   32-block  0
                   #####:   33:    printf ("Failure\n");
                   %%%%%:   33-block  0
                       -:   34:  else
                       1:   35:    printf ("Success\n");
                       1:   35-block  0
                       1:   36:  return 0;
                       1:   36-block  0
                       -:   37:}

       In  this  mode,  each  basic block is only shown on one line -- the last line of the block.  A multi-line
       block will only contribute to the execution count of that last line, and other lines will not be shown to
       contain code, unless previous blocks end on those lines.  The total execution count of a  line  is  shown
       and  subsequent  lines show the execution counts for individual blocks that end on that line.  After each
       block, the branch and call counts of the block will be shown, if the -b option is given.

       Because of the way GCC instruments calls, a call count can be shown  after  a  line  with  no  individual
       blocks.  As you can see, line 33 contains a basic block that was not executed.

       When you use the -b option, your output looks like this:

                       -:    0:Source:tmp.cpp
                       -:    0:Graph:tmp.gcno
                       -:    0:Data:tmp.gcda
                       -:    0:Runs:1
                       -:    0:Programs:1
                       -:    1:#include <stdio.h>
                       -:    2:
                       -:    3:template<class T>
                       -:    4:class Foo
                       -:    5:{
                       -:    6:  public:
                      1*:    7:  Foo(): b (1000) {}
               ------------------
               Foo<char>::Foo():
               function Foo<char>::Foo() called 0 returned 0% blocks executed 0%
                   #####:    7:  Foo(): b (1000) {}
               ------------------
               Foo<int>::Foo():
               function Foo<int>::Foo() called 1 returned 100% blocks executed 100%
                       1:    7:  Foo(): b (1000) {}
               ------------------
                      2*:    8:  void inc () { b++; }
               ------------------
               Foo<char>::inc():
               function Foo<char>::inc() called 0 returned 0% blocks executed 0%
                   #####:    8:  void inc () { b++; }
               ------------------
               Foo<int>::inc():
               function Foo<int>::inc() called 2 returned 100% blocks executed 100%
                       2:    8:  void inc () { b++; }
               ------------------
                       -:    9:
                       -:   10:  private:
                       -:   11:  int b;
                       -:   12:};
                       -:   13:
                       -:   14:template class Foo<int>;
                       -:   15:template class Foo<char>;
                       -:   16:
                       -:   17:int
               function main called 1 returned 100% blocks executed 81%
                       1:   18:main (void)
                       -:   19:{
                       -:   20:  int i, total;
                       1:   21:  Foo<int> counter;
               call    0 returned 100%
               branch  1 taken 100% (fallthrough)
               branch  2 taken 0% (throw)
                       -:   22:
                       1:   23:  counter.inc();
               call    0 returned 100%
               branch  1 taken 100% (fallthrough)
               branch  2 taken 0% (throw)
                       1:   24:  counter.inc();
               call    0 returned 100%
               branch  1 taken 100% (fallthrough)
               branch  2 taken 0% (throw)
                       1:   25:  total = 0;
                       -:   26:
                      11:   27:  for (i = 0; i < 10; i++)
               branch  0 taken 91% (fallthrough)
               branch  1 taken 9%
                      10:   28:    total += i;
                       -:   29:
                      1*:   30:  int v = total > 100 ? 1 : 2;
               branch  0 taken 0% (fallthrough)
               branch  1 taken 100%
                       -:   31:
                       1:   32:  if (total != 45)
               branch  0 taken 0% (fallthrough)
               branch  1 taken 100%
                   #####:   33:    printf ("Failure\n");
               call    0 never executed
               branch  1 never executed
               branch  2 never executed
                       -:   34:  else
                       1:   35:    printf ("Success\n");
               call    0 returned 100%
               branch  1 taken 100% (fallthrough)
               branch  2 taken 0% (throw)
                       1:   36:  return 0;
                       -:   37:}

       For  each  function,  a  line is printed showing how many times the function is called, how many times it
       returns and what percentage of the function's blocks were executed.

       For each basic block, a line is printed after the last line of the basic block describing the  branch  or
       call that ends the basic block.  There can be multiple branches and calls listed for a single source line
       if  there are multiple basic blocks that end on that line.  In this case, the branches and calls are each
       given a number.  There is no simple way to map these branches and calls back to  source  constructs.   In
       general,  though,  the  lowest  numbered  branch or call will correspond to the leftmost construct on the
       source line.

       For a branch, if it was executed at least once, then a percentage indicating  the  number  of  times  the
       branch  was taken divided by the number of times the branch was executed will be printed.  Otherwise, the
       message "never executed" is printed.

       For a call, if it was executed at least once, then a percentage indicating the number of times  the  call
       returned  divided  by  the  number  of times the call was executed will be printed.  This will usually be
       100%, but may be less for functions that call "exit" or "longjmp", and thus may  not  return  every  time
       they are called.

       The  execution  counts  are  cumulative.  If the example program were executed again without removing the
       .gcda file, the count for the number of times each line in the source was executed would be added to  the
       results  of  the  previous run(s).  This is potentially useful in several ways.  For example, it could be
       used to accumulate data over a number of program runs as part of a test verification suite, or to provide
       more accurate long-term information over a large number of program runs.

       The data in the .gcda files is saved immediately before the program exits.  For each source file compiled
       with -fprofile-arcs, the profiling code first attempts to read in an existing .gcda  file;  if  the  file
       doesn't  match the executable (differing number of basic block counts) it will ignore the contents of the
       file.  It then adds in the new execution counts and finally writes the data to the file.

   Using gcov with GCC Optimization
       If you plan to use gcov to help optimize your code, you must first compile your program with two  special
       GCC  options: -fprofile-arcs -ftest-coverage.  Aside from that, you can use any other GCC options; but if
       you want to prove that every single line in your program  was  executed,  you  should  not  compile  with
       optimization  at  the  same time.  On some machines the optimizer can eliminate some simple code lines by
       combining them with other lines.  For example, code like this:

               if (a != b)
                 c = 1;
               else
                 c = 0;

       can be compiled into one instruction on some machines.  In this  case,  there  is  no  way  for  gcov  to
       calculate separate execution counts for each line because there isn't separate code for each line.  Hence
       the gcov output looks like this if you compiled the program with optimization:

                     100:   12:if (a != b)
                     100:   13:  c = 1;
                     100:   14:else
                     100:   15:  c = 0;

       The  output  shows  that  this block of code, combined by optimization, executed 100 times.  In one sense
       this result is correct, because there was only one instruction representing  all  four  of  these  lines.
       However,  the  output does not indicate how many times the result was 0 and how many times the result was
       1.

       Inlineable functions can create unexpected line counts.  Line counts are shown for the source code of the
       inlineable function, but what is shown depends on where the function is inlined, or if it is not  inlined
       at all.

       If the function is not inlined, the compiler must emit an out of line copy of the function, in any object
       file  that  needs  it.  If fileA.o and fileB.o both contain out of line bodies of a particular inlineable
       function, they will also both contain coverage counts for that function.  When fileA.o  and  fileB.o  are
       linked  together,  the linker will, on many systems, select one of those out of line bodies for all calls
       to that function, and remove or ignore the  other.   Unfortunately,  it  will  not  remove  the  coverage
       counters  for  the  unused function body.  Hence when instrumented, all but one use of that function will
       show zero counts.

       If the function is inlined in several places, the block structure in each location might not be the same.
       For instance, a condition might now be calculable  at  compile  time  in  some  instances.   Because  the
       coverage  of all the uses of the inline function will be shown for the same source lines, the line counts
       themselves might seem inconsistent.

       Long-running applications can use the "__gcov_reset" and "__gcov_dump"  facilities  to  restrict  profile
       collection  to  the  program  region  of  interest.  Calling  "__gcov_reset(void)" will clear all profile
       counters to zero, and calling "__gcov_dump(void)" will cause the profile information  collected  at  that
       point  to  be  dumped  to  .gcda  output  files.   Instrumented applications use a static destructor with
       priority 99 to invoke the "__gcov_dump" function. Thus "__gcov_dump" is executed after all  user  defined
       static  destructors,  as  well  as  handlers  registered with "atexit".  If an executable loads a dynamic
       shared object via dlopen functionality, -Wl,--dynamic-list-data is needed to dump all profile data.

SEE ALSO

       gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entry for gcc.

COPYRIGHT

       Copyright (c) 1996-2018 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms  of  the  GNU  Free
       Documentation  License,  Version 1.3 or any later version published by the Free Software Foundation; with
       the Invariant Sections being "GNU General Public License" and "Funding Free  Software",  the  Front-Cover
       texts  being (a) (see below), and with the Back-Cover Texts being (b) (see below).  A copy of the license
       is included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.

gcc-8.4.0                                          2020-03-04                                            GCOV(1)