GCOV-TOOL(1)

📦
version 14.4.1 · 3 versions
, in fedora 43

💖 GCOV-TOOL 💖

okay bestie, welcome to the gcov-tool page from the GNU fam 🫶 it's the offline gcda profile processing tool and honestly? it eats. let's get into it 💅

✨ NAME ✨

gcov-tool — offline gcda profile processing tool 🎀

🌸 SYNOPSIS 🌸

like, here's the whole vibe in one look 👀

gcov-tool [-v|--version] [-h|--help]

gcov-tool merge [merge-options] directory1 directory2
     [-o|--output directory]
     [-v|--verbose]
     [-w|--weight w1,w2]

gcov-tool merge-stream [merge-stream-options] [file]
     [-v|--verbose]
     [-w|--weight w1,w2]

gcov-tool rewrite [rewrite-options] directory
     [-n|--normalize long_long_value]
     [-o|--output directory]
     [-s|--scale float_or_simple-frac_value]
     [-v|--verbose]

gcov-tool overlap [overlap-options] directory1 directory2
     [-f|--function]
     [-F|--fullname]
     [-h|--hotonly]
     [-o|--object]
     [-t|--hot_threshold] float
     [-v|--verbose]

🦋 DESCRIPTION 🦋

so gcov-tool is an offline tool that processes gcc's gcda profile files. no cap. 💖

rn gcov-tool supports these functionalities, and yes I'm listing all of them because we don't skip:

  • merge two sets of profiles with weights. ⚖️
  • read a stream of profiles with associated filenames and merge it with a set of profiles with weights. 🌊
  • read one set of profile and rewrite profile contents. One can scale or normalize the count values. 🔁

Examples of the use cases for this tool are — and these are literally the moments where this thing is the main character:

  • Collect the profiles for different set of inputs, and use this tool to merge them. One can specify the weight to factor in the relative importance of each input. 👑
  • Collect profiles from target systems without a filesystem (freestanding environments). Merge the collected profiles with associated profiles present on the host system. One can specify the weight to factor in the relative importance of each input. 🛰️
  • Rewrite the profile after removing a subset of the gcda files, while maintaining the consistency of the summary and the histogram. 🧹
  • It can also be used to debug or libgcov code as the tools shares the majority code as the runtime library. 🐛
heads up bestie ⚠️ Note that for the merging operation, this profile generated offline may contain slight different values from the online merged profile.

Here are a list of typical differences, so you're not caught off guard 🙈:

  • histogram difference: This offline tool recomputes the histogram after merging the counters. The resulting histogram, therefore, is precise. The online merging does not have this capability — the histogram is merged from two histograms and the result is an approximation. 📊
  • summary checksum difference: Summary checksum uses a CRC32 operation. The value depends on the link list order of gcov-info objects. This order is different in gcov-tool from that in the online merge. It's expected to have different summary checksums. It does not really matter as the compiler does not use this checksum anywhere. 🤷‍♀️
  • value profile counter values difference: Some counter values for value profile are runtime dependent, like heap addresses. It's normal to see some difference in these kind of counters. 🧮

👑 OPTIONS 👑

  • -h, --help — Display help about using gcov-tool (on the standard output), and exit without doing any further processing. your lil "what does this do again" button 🥺
  • -v, --version — Display the gcov-tool version number (on the standard output), and exit without doing any further processing. 💫
  • merge — Merge two profile directories. 🫂
    • -o directory, --output directory — Set the output profile directory. Default output directory name is merged_profile.
    • -v, --verbose — Set the verbose mode. 🗣️
    • -w w1,w2, --weight w1,w2 — Set the merge weights of the directory1 and directory2, respectively. The default weights are 1 for both. ⚖️
  • merge-stream — Collect profiles with associated filenames from a gcfn and gcda data stream. Read the stream from the file specified by file or from stdin. Merge the profiles with associated profiles in the host filesystem. Apply the optional weights while merging profiles. 🌊✨

For the generation of a gcfn and gcda data stream on the target system, please have a look at the "__gcov_filename_to_gcfn()" and "__gcov_info_to_gcda()" functions declared in "#include <gcov.h>". 🧚

  • -v, --verbose — Set the verbose mode. 🗣️
  • -w w1,w2, --weight w1,w2 — Set the merge weights of the profiles from the gcfn and gcda data stream and the associated profiles in the host filesystem, respectively. The default weights are 1 for both. ⚖️
  • rewrite — Read the specified profile directory and rewrite to a new directory. 📝
    • -n long_long_value, --normalize <long_long_value> — Normalize the profile. The specified value is the max counter value in the new profile. 🎚️
    • -o directory, --output directory — Set the output profile directory. Default output name is rewrite_profile.
    • -s float_or_simple-frac_value, --scale float_or_simple-frac_value — Scale the profile counters. The specified value can be in floating point value, or simple fraction value form, such 1, 2, 2/3, and 5/3. 🔢
    • -v, --verbose — Set the verbose mode. 🗣️
  • overlap — Compute the overlap score between the two specified profile directories. The overlap score is computed based on the arc profiles. It is defined as the sum of min (p1_counter[i] / p1_sum_all, p2_counter[i] / p2_sum_all), for all arc counter i, where p1_counter[i] and p2_counter[i] are two matched counters and p1_sum_all and p2_sum_all are the sum of counter values in profile 1 and profile 2, respectively. 💞
    • -f, --function — Print function level overlap score. 🧩
    • -F, --fullname — Print full gcda filename. 🏷️
    • -h, --hotonly — Only print info for hot objects/functions. 🔥
    • -o, --object — Print object level overlap score. 📦
    • -t float, --hot_threshold <float> — Set the threshold for hot counter value. 🌡️
    • -v, --verbose — Set the verbose mode. 🗣️

🌈 SEE ALSO 🌈

gpl(7), gfdl(7), fsf-funding(7), gcc(1), gcov(1) and the Info entry for gcc. go read those too, they're giving lore 📚

Copyright (c) 2014-2024 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.

and that's the whole page bestie!! 🌟 this one's from gcc-14, dated 2026-07-24 — go forth and merge those profiles, you got this fr fr 💅✨🍓

📦 where this page comes from
  • fedora 43: gcc14 14.4.1-2.fc43 · GPL-3.0-or-later AND LGPL-3.0-or-later AND (GPL-3.0-or-later WITH GCC-exception-3.1) AND (GPL-3.0-or-later WITH Texinfo-exception) AND (LGPL-2.1-or-later WITH GCC-exception-2.0) AND (GPL-2.0-or-later WITH GCC-exception-2.0) AND (GPL-2.0-or-later WITH GNU-compiler-exception) AND BSL-1.0 AND GFDL-1.3-or-later AND Linux-man-pages-copyleft-2-para AND SunPro AND BSD-1-Clause AND BSD-2-Clause AND BSD-2-Clause-Views AND BSD-3-Clause AND BSD-4-Clause AND BSD-Source-Code AND Zlib AND MIT AND Apache-2.0 AND (Apache-2.0 WITH LLVM-Exception) AND ZPL-2.1 AND curl
  • 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on : a language model's rewrite of the original, under its terms