GCOV(1)

πŸ“¦ version 14.2.0, in ubuntu noble

πŸ’– GCOV(1) β€” the GNU coverage testing tool, but make it a group chat πŸ’–

okay so bestie, welcome to gcov, brought to you by the GNU girlies, man page section 1, no cap. this is the one that tells you which of your lines actually ran. let's get into it ✨


🌸 NAME 🌸

gcov β€” coverage testing tool 🧚


πŸŽ€ SYNOPSIS πŸŽ€

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

✨ DESCRIPTION ✨

so gcov is a test coverage program πŸ’…. you use it in concert with GCC to analyze your programs, which helps you build more efficient, faster-running code, and also helps you find the parts of your program that nobody ever tested (the untested parts, we see them πŸ‘€). you can also run gcov as a profiling tool to figure out where your optimization efforts will hit the hardest. and plot twist β€” you can run it alongside the other profiling tool, gprof, to assess which parts of your code are eating up the most computing time. clocked πŸ“Š

profiling tools help you analyze your code's performance. using a profiler like gcov or gprof, you can find out some basic performance stats, like:

  • 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 behaves when it's compiled, you can look at each module and see which modules should be optimized. gcov helps you determine where to do the optimization work. main character tool behavior, honestly πŸ‘‘

software developers also use coverage testing in concert with testsuites, to make sure the 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 actually exercised by that testsuite. then developers can figure out what kinds of test cases need to be added to the testsuites, so they get both better testing and a better final product. glow-up for everyone 🌈

⚠️ bestie, listen: 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. also, 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 β€” 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. periodt.

gcov creates a logfile called sourcefile.gcov which tells you how many times each line of a source file sourcefile.c has executed. you can use these logfiles along with gprof to help fine-tune the performance of your programs β€” gprof gives you timing information you can use right alongside the info you get from gcov. dynamic duo fr fr 🫢

πŸ’€ and this is the important one: gcov works only on code compiled with GCC. it is not compatible with any other profiling or test coverage mechanism. no exceptions, no crossover episodes, sorry bestie.

πŸ‘‘ OPTIONS πŸ‘‘

  • -a, --all-blocks β€” 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 πŸ”
  • -b, --branch-probabilities β€” write branch frequencies to the output file, and write branch summary info to standard output. this lets you see how often each branch in your program was taken. unconditional branches will not be shown, unless the -u option is given. iykyk
  • -c, --branch-counts β€” write branch frequencies as the number of branches taken, rather than the percentage of branches taken. receipts, not vibes πŸ“ˆ
  • -g, --conditions β€” write condition coverage to the output file, and write condition summary info to standard output. this lets you see if the conditions in your program at least once had an independent effect on the outcome of the boolean expression (that's modified condition/decision coverage, bestie). this requires you to compile the source with -fcondition-coverage ⭐
  • -d, --display-progress β€” display the progress on standard output. we love a loading bar moment ✨
  • -f, --function-summaries β€” output summaries for each function, in addition to the file level summary. every function gets its moment πŸ’–
  • -h, --help β€” display help about using gcov (on standard output), and exit without doing any further processing. bye bestie πŸ‘‹
  • -j, --json-format β€” output the gcov file in an easy-to-parse JSON intermediate format which does not require source code for generation. the JSON file is compressed with the gzip compression algorithm and the files have the .gcov.json.gz extension. so cute, so parseable πŸŽ€

structure of the JSON is the following:

{
  "current_working_directory": "foo/bar",
  "data_file": "a.out",
  "format_version": "2",
  "gcc_version": "11.1.1 20210510"
  "files": ["$file"]
}

fields of the root element have the following semantics:

  • current_working_directory: working directory where a compilation unit was compiled
  • data_file: name of the data file (GCDA)
  • format_version: semantic version of the format

changes in version 2:

  • calls: information about function calls is added
  • gcc_version: version of the GCC compiler

each file has the following form:

{
  "file": "a.c",
  "functions": ["$function"],
  "lines": ["$line"]
}

fields of the file element have the following semantics:

  • file_name: name of the source file

each function has the following form:

{
  "blocks": 2,
  "blocks_executed": 2,
  "demangled_name": "foo",
  "end_column": 1,
  "end_line": 4,
  "execution_count": 1,
  "name": "foo",
  "start_column": 5,
  "start_line": 1
}

fields of the function element have the following semantics:

  • blocks: number of blocks that are in the function
  • blocks_executed: number of executed blocks of the function
  • demangled_name: demangled name of the function
  • end_column: column in the source file where the function ends
  • end_line: line in the source file where the function ends
  • execution_count: number of executions of the function
  • name: name of the function
  • start_column: column in the source file where the function begins
  • start_line: line in the source file where the function begins
πŸ™ˆ note that line numbers and column numbers number from 1. in the current implementation, start_line and start_column do not include any template parameters and the leading return type, but that this is likely to be fixed in the future.

each line has the following form:

{
  "block_ids": ["$block_id"],
  "branches": ["$branch"],
  "calls": ["$call"],
  "count": 2,
  "conditions": ["$condition"],
  "line_number": 15,
  "unexecuted_block": false,
  "function_name": "foo",
}

branches and calls are present only with the -b option. fields of the line element have the following semantics:

  • block_ids: IDs of basic blocks that belong to the line
  • count: number of executions of the line
  • line_number: line number
  • unexecuted_block: flag whether the line contains an unexecuted block (not all statements on the line are executed)
  • function_name: a name of a function this line belongs to (for a line with an inlined statements can be not set)

each branch has the following form:

{
  "count": 11,
  "destination_block_id": 17,
  "fallthrough": true,
  "source_block_id": 13,
  "throw": false
}

fields of the branch element have the following semantics:

  • count: number of executions of the branch
  • fallthrough: true when the branch is a fall through branch
  • throw: true when the branch is an exceptional branch
  • isource_block_id: ID of the basic block where this branch happens
  • destination_block_id: ID of the basic block this branch jumps to

each call has the following form:

{
  "destination_block_id": 1,
  "returned": 11,
  "source_block_id": 13
}

fields of the call element have the following semantics:

  • returned: number of times a function call returned (call count is equal to line::count)
  • isource_block_id: ID of the basic block where this call happens
  • destination_block_id: ID of the basic block this calls continues after return

each condition has the following form:

{
  "count": 4,
  "covered": 2,
  "not_covered_false": [],
  "not_covered_true": [0, 1],
}

fields of the condition element have the following semantics:

  • count: number of condition outcomes in this expression
  • covered: number of covered condition outcomes in this expression
  • not_covered_true: terms, by index, not seen as true in this expression
  • not_covered_false: terms, by index, not seen as false in this expression
  • -H, --human-readable β€” write counts in human readable format (like 24.6k). because reading raw integers is not the vibe πŸ’…
  • -k, --use-colors β€” 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 the -a option 🌈
  • -l, --long-file-names β€” okay so this one makes long file names for included source files. Like, say the header file x.h contains code, and it was included in the file a.c β€” then running gcov on a.c will produce an output file called a.c##x.h.gcov instead of x.h.gcov. obsessed ✨ This is useful if x.h is included in multiple source files and you want to see the individual contributions. And if you use the -p option, both the including and the included file names will be complete path names. πŸ’…
  • -m, --demangled-names β€” displays demangled function names in the output. The default is to show mangled function names, so this is the glow-up. 🫢
  • -n, --no-output β€” do not create the gcov output file. That's the whole thing bestie, it just... doesn't. πŸ’€
  • -o directory|file, --object-directory directory, --object-file file β€” 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 β€” preserves 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 your source files are in several different directories. πŸ¦‹
  • -q, --use-hotness-colors β€” emits perf-like colored output for hot lines πŸ”₯. Legend of the color scale is printed at the very beginning of the output file. Iconic.
  • -r, --relative-only β€” only outputs 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. πŸ™ˆ
  • -s directory, --source-prefix directory β€” 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. ⭐
  • -t, --stdout β€” outputs to standard output instead of output files. ✨
  • -u, --unconditional-branches β€” when branch probabilities are given, include those of unconditional branches. Unconditional branches are normally not interesting, so like, do with that what you will. πŸŽ€
  • -v, --version β€” displays the gcov version number (on the standard output), and exits without doing any further processing. Main character exit. πŸ‘‘
  • -w, --verbose β€” prints verbose informations related to basic blocks and arcs. πŸ”
  • -x, --hash-filenames β€” when you're using --preserve-paths, 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. The option is an alternative to the --preserve-paths on systems which have a filesystem limit. πŸ’œ

okay bestie, now the actual how-to, because there's lore here πŸ’–

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 the -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 the -k option. This 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. πŸ’…

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. πŸ‘€

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. πŸ€–

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. no cap, it's precise like that ✨

When using gcov, you must first compile your program with a special GCC option --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. πŸ—οΈ

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. πŸ“

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++ --coverage tmp.cpp -c
$ g++ --coverage tmp.o
$ 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:Working directory:/home/gcc/testcase
                -:    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:Working directory:/home/gcc/testcase
                       -:    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:}

okay so bestie, in this mode each basic block gets shown on exactly one line β€” the last line of the block, periodt. A multi-line block only counts toward the execution count of that last line, and the other lines won't show as containing code unless previous blocks happen to end on them. The total execution count of a line gets shown, and then the lines after it show the execution counts for the individual blocks that end on that line. And after each block, the branch and call counts of that block get printed too, but only if the -b option is given πŸ‘€

Because of the way GCC instruments calls, a call count can show up after a line with no individual blocks. And as you can literally see up there, line 33 contains a basic block that was not executed. πŸ’€

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

                       -:    0:Source:tmp.cpp
                       -:    0:Working directory:/home/gcc/testcase
                       -:    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 every function, a line gets printed showing how many times the function is called, how many times it returns, and what percentage of the function's blocks were executed. slay. ✨

For every basic block, a line gets 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 β€” and in that case, the branches and calls are each given a number. Ngl there's 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. iykyk 🧚

For a branch: if it was executed at least once, then a percentage gets printed, showing the number of times the branch was taken divided by the number of times the branch was executed. Otherwise, the message "never executed" gets printed.

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

The execution counts are cumulative. So 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). And honestly? That's 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. main character energy fr fr πŸ‘‘

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. the way it just. does all that. πŸ’…


🌈 Using gcov with GCC Optimization 🌈

If you're planning to use gcov to help optimize your code, you must first compile your program with a special GCC option: --coverage. Aside from that, you can use any other GCC options β€” 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. And 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. it's giving "technically true but emotionally unhelpful" πŸ’€

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. πŸ¦‹

okay so bestie, if a function is not inlined, the compiler literally has to emit an out-of-line copy of it in any object file that needs it. So 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. But here's the tea β˜•: 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. πŸ’€

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. πŸ™ˆ

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 run-time 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. πŸ‘‘

Profiling run-time library reports various errors related to profile manipulation and profile saving. Errors are printed into standard error output or GCOV_ERROR_FILE file, if environment variable is used. In order to terminate immediately after an error occurs set GCOV_EXIT_AT_ERROR environment variable. That can help users to find profile clashing which leads to a misleading profile. πŸ”₯


πŸ‘€ SEE ALSO πŸ‘€

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


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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.

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A GNU Manual

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That's the whole vibe, bestie! This page was from gcc-14.2.0, dated 2024-08-01, and it's the GCOV(1) manual. Stay slaying! πŸ’…βœ¨πŸ’–

πŸ“¦ where this page comes from