GCOV-TOOL(1)

💅 GCOV-TOOL 💅

okay so bestie, welcome to gcov-tool from the GNU fam — this is the gcov-tool(1) manual page and it's literally about an offline gcda profile processing tool. yes, "offline profile processing" sounds like a vibe check nobody asked for, but stay with me, it's actually iconic 🫶

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✨ NAME ✨

gcov-tool — the offline gcda profile processing tool. that's it, that's the whole name, and it ate 💅

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🦋 SYNOPSIS 🦋

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]

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🌸 DESCRIPTION 🌸

so gcov-tool is an offline tool that processes gcc's gcda profile files. no network, no drama, just files on your disk getting handled. periodt.

rn gcov-tool supports these functionalities, and honestly? the range:

• merge two sets of profiles with weights. lowkey the main character of this tool.
• 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. slay.

Examples of the use cases for this tool are — bestie, the lore:

• 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. iykyk.
• 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. (yes the weight thing comes up twice, it's important 💅)
• rewrite the profile after removing a subset of the gcda files, while maintaining the consistency of the summary and the histogram. ✨ consistency ✨
• it can also be used to debug or libgcov code as the tools shares the majority code as the runtime library. (yes, the sentence says "to debug or libgcov code" — that's canon, don't @ me)

⚠️ heads up bestie: for the merging operation, this profile generated offline may contain slight different values from the online merged profile. not a bug, just how it is. here's a list of typical differences:

• 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 stays winning 🏆
• 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. not me getting emotionally attached to a heap address 😭

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🎀 OPTIONS 🎀

• -h, --help — display help about using gcov-tool (on the standard output), and exit without doing any further processing. the "i'm out" option, respectfully.
• -v, --version — display the gcov-tool version number (on the standard output), and exit without doing any further processing. same energy, different info.

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💫 merge 💫

merge two profile directories. two directories walk into a bar… and become one 🫶

• -o directory, --output directory — set the output profile directory. default output directory name is merged_profile. (that's the default, don't come for me)
• -v, --verbose — set the verbose mode. she talks more. 🗣️
• -w w1,w2, --weight w1,w2 — set the merge weights of the directory1 and directory2, respectively. the default weights are 1 for both. balance is everything. ⚖️

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🧚 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. it's giving "long distance relationship but make it 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>. that's where the magic happens, go read it ✨

• -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. yes, 1 and 1 again, the default weights are consistently unbothered 💅

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⭐ rewrite ⭐

read the specified profile directory and rewrite to a new directory. glow-up arc, but for counters.

• -n long_long_value, --normalize <long_long_value> — normalize the profile. the specified value is the max counter value in the new profile. like a ceiling but make it cute. 📏
• -o directory, --output directory — set the output profile directory. default output name is rewrite_profile. remember it, write it down, tattoo it.
• -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. math girlies rise 🧮
• -v, --verbose — set the verbose mode.

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🔥 overlap 🔥

compute the overlap score between the two specified profile directories. the overlap score is computed based on the arc profiles. the definition, verbatim bestie, is:

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.

no cap, that's the actual formula. screenshot it. 📸

• -f, --function — print function level overlap score. zoom in on the functions.
• -F, --fullname — print full gcda filename. no shortening, no nicknames, full government name 🪪
• -h, --hotonly — only print info for hot objects/functions. hot girl summer but it's counters 🥵
• -o, --object — print object level overlap score. zoom out, object level.
• -t float, --hot_threshold <float> — set the threshold for hot counter value. where "hot" begins is your call.
• -v, --verbose — set the verbose mode.

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🌈 SEE ALSO 🌈

go read these too, they're all in the group chat: gpl(7), gfdl(7), fsf-funding(7), gcc(1), gcov(1) and the Info entry for gcc. 💖

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👑 COPYRIGHT 👑

Copyright (c) 2014-2023 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.

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and that's the whole page bestie, you're officially a gcov-tool girlie now 🎀✨ this was the gcc-13 era of the page, dated 2026-09-10 — same energy as the original footer, just with better vibes. go forth and merge responsibly 💜🦋