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    Command:

    gcov

    
    
    

    SYNOPSIS

           gcov [-v|--version] [-h|--help]
                [-a|--all-blocks]
                [-b|--branch-probabilities]
                [-c|--branch-counts]
                [-n|--no-output]
                [-l|--long-file-names]
                [-p|--preserve-paths]
                [-f|--function-summaries]
                [-o|--object-directory directory|file] sourcefiles
                [-u|--unconditional-branches]
    
    
    

    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.
           --help
               Display help about using gcov (on the standard output), and exit
               without doing any further processing.
    
           -v
           --version
               Display the gcov version number (on the standard output), and exit
               without doing any further processing.
    
           -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.
    
           -n
           --no-output
               Do not create the gcov output file.
    
           -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.  If you use the -p
               option, both the including and included file names will be complete
               path names.
    
           -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 ..
               components renamed to ^.  This is useful if sourcefiles are in
               several different directories.  It also affects the -l option.
    
           -f
    
           -u
           --unconditional-branches
               When branch probabilities are given, include those of unconditional
               branches.  Unconditional branches are normally not interesting.
    
           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 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.
    
           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 and ##### for lines which were never executed.  Some lines of
           information at the start have line_number of zero.
    
           The 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
                   90.00% of 10 source lines executed in file tmp.c
                   Creating tmp.c.gcov.
    
           The file tmp.c.gcov contains output from gcov.  Here is a sample:
    
                           -:    0:Source:tmp.c
                           -:    0:Graph:tmp.gcno
                           -:    0:Data:tmp.gcda
                           -:    0:Runs:1
                           -:    0:Programs:1
                           -:    1:#include <stdio.h>
                           -:    2:
                           -:    3:int main (void)
                           1:    4:{
                           1:    5:  int i, total;
                           -:    6:
                           1:    7:  total = 0;
                           -:    8:
                          11:    9:  for (i = 0; i < 10; i++)
                          10:   10:    total += i;
                           -:   11:
                           1:   12:  if (total != 45)
                       #####:   13:    printf ("Failure\n");
                           -:   14:  else
                           1:   15:    printf ("Success\n");
                           1:   16:  return 0;
                           -:   17:}
    
           When you use the -a option, you will get individual block counts, and
           the output looks like this:
    
                           -:    0:Source:tmp.c
                           -:    0:Graph:tmp.gcno
                           -:    0:Data:tmp.gcda
                           -:    0:Runs:1
                           -:    0:Programs:1
                           -:    1:#include <stdio.h>
                           -:    2:
                           -:    3:int main (void)
                           1:    4:{
                           1:    4-block  0
                           1:    5:  int i, total;
                           -:    6:
                           1:    7:  total = 0;
                           -:    8:
                          11:    9:  for (i = 0; i < 10; i++)
                          11:    9-block  0
                          10:   10:    total += i;
                          10:   10-block  0
                           -:   11:
                           1:   12:  if (total != 45)
                           1:   12-block  0
    
           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 13
           contains a basic block that was not executed.
    
           When you use the -b option, your output looks like this:
    
                   $ gcov -b tmp.c
                   90.00% of 10 source lines executed in file tmp.c
                   80.00% of 5 branches executed in file tmp.c
                   80.00% of 5 branches taken at least once in file tmp.c
                   50.00% of 2 calls executed in file tmp.c
                   Creating tmp.c.gcov.
    
           Here is a sample of a resulting tmp.c.gcov file:
    
                           -:    0:Source:tmp.c
                           -:    0:Graph:tmp.gcno
                           -:    0:Data:tmp.gcda
                           -:    0:Runs:1
                           -:    0:Programs:1
                           -:    1:#include <stdio.h>
                           -:    2:
                           -:    3:int main (void)
                   function main called 1 returned 1 blocks executed 75%
                           1:    4:{
                           1:    5:  int i, total;
                           -:    6:
                           1:    7:  total = 0;
                           -:    8:
                          11:    9:  for (i = 0; i < 10; i++)
                   branch  0 taken 91% (fallthrough)
                   branch  1 taken 9%
                          10:   10:    total += i;
                           -:   11:
                           1:   12:  if (total != 45)
                   branch  0 taken 0% (fallthrough)
                   branch  1 taken 100%
                       #####:   13:    printf ("Failure\n");
                   call    0 never executed
                           -:   14:  else
                           1:   15:    printf ("Success\n");
                   call    0 called 1 returned 100%
                           1:   16:  return 0;
                           -:   17:}
    
           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 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
           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.
    
    
    

    SEE ALSO

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

    COPYRIGHT

           Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
           2008  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 1.2 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-4.4.7 2012-03-13 GCOV(1)

    
    
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