GCOV-TOOL(1)

📦 version 12.1.1, in epel 9

💅 GCOV-TOOL(1) — the offline gcda profile glow-up tool ✨

okay so bestie, this is a page from the GNU manual set, and honestly? it's giving "niche but iconic." let's get into it 🫶

✨ NAME ✨

gcov-tool — the offline gcda profile processing tool. yes, offline. no cap. 🎀

🌸 SYNOPSIS 🌸

here's the whole vibe menu, literally copy-paste it:

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

gcov-tool merge [merge-options] directory1 directory2
     [-o|--output directory]
     [-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]

like, pick a mode, pick your dirs, sprinkle your flags. slay. 💅

🦋 DESCRIPTION 🦋

so gcov-tool is an offline tool that processes gcc's gcda profile files. lowkey a little sidekick to the compiler, but it's doing the most.

right now gcov-tool supports these functionalities:

  • merge two sets of profiles with weights. 🧚
  • read one set of profile and rewrite profile contents. you can scale or normalize the count values. literally so useful.

examples of the use cases for this tool are:

  • collect the profiles for different set of inputs, and use this tool to merge them. you can specify the weight to factor in the relative importance of each input. main character energy for real.
  • rewrite the profile after removing a subset of the gcda files, while maintaining the consistency of the summary and the histogram. obsessed. 🩷
  • it can also be used to debug or libgcov code as the tools shares the majority code as the runtime library.
⚠️ ok bestie listen — for the merging operation, this profile generated offline may contain slight different values from the online merged profile. like, it's fine, but here's a list of typical differences so you're not surprised:
  • 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. offline really said "I'll do it myself." 💀
  • 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. so like... breathe. 😮‍💨
  • 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. that's just how it is fr fr.

💖 OPTIONS 💖

the basics ✨

  • -h, --help — display help about using gcov-tool (on the standard output), and exit without doing any further processing. your little "wait 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. just the digits, then it dips.

🌈 merge — merge two profile directories

💫 the options

  • -o directory, --output directory — set the output profile directory. default output directory name is merged_profile. honestly a cute default.
  • -v, --verbose — set the verbose mode. it will yap (affectionate). 🗣️
  • -w w1,w2, --weight w1,w2 — set the merge weights of the directory1 and directory2, respectively. the default weights are 1 for both. balanced, as all things should be ⚖️

🎀 rewrite — read the specified profile directory and rewrite to a new directory

💫 the options

  • -n long_long_value, --normalize long_long_value — normalize the profile. the specified value is the max counter value in the new profile. giving everything a little ceiling ✨
  • -o directory, --output directory — set the output profile directory. default output name is rewrite_profile. yes it's lowercase and has an underscore, keep it exactly like that bestie.
  • -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. fractions ate, ngl 🍓
  • -v, --verbose — set the verbose mode.

🧚 overlap — compute the overlap score between the two specified profile directories

okay so 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. like a compatibility quiz but for profiles 💜

💫 the options

  • -f, --function — print function level overlap score. zoom in on the functions 🔍
  • -F, --fullname — print full gcda filename. no shortening, no nicknames.
  • -h, --hotonly — only print info for hot objects/functions. 🔥 only the baddies.
  • -o, --object — print object level overlap score. zoom out to the objects.
  • -t float, --hot_threshold float — set the threshold for hot counter value. you decide what counts as "hot" 👑
  • -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, iykyk 🌟

Copyright (c) 2014-2022 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-12, dated 2022-05-07 — so it's got a little vintage moment going on, but it still slays. mwah 💋

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