GCOV-TOOL(1)

📦
version 12-20220319 · 4 versions
, in ubuntu jammy

💖 NAME 💖

gcov-tool — the offline gcda profile processing tool, bestie ✨

🦋 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 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 🌸

Okay so gcov-tool is an offline tool for processing gcc's gcda profile files. It does its thing after the fact, no live runtime needed, periodt. 💅

Right now, gcov-tool supports these functionalities:

  • merge two sets of profiles with weights. 🫶
  • read one set of profile and rewrite the profile contents. You can scale or normalize the count values.

Examples of use cases for this tool, because I know you're gonna ask:

  • Collect the profiles for different sets of inputs, then use this tool to merge them. You 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 keeping the consistency of the summary and the histogram. 🎀
  • It can also be used to debug or libgcov code, because the tool shares the majority of its code with the runtime library. 🧚
Heads up bestie ⚠️ — for the merging operation, this profile generated offline may contain slightly different values from the online merged profile. Here's the list of typical differences:
  • histogram difference: This offline tool recomputes the histogram after merging the counters. The resulting histogram is therefore 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 doesn't really matter though, because 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 kinds of counters. 🌈

✨ OPTIONS ✨

  • -h, --help — Display help about using gcov-tool (on the standard output), and exit without doing any further processing. Ask and ye shall receive. 🫶
  • -v, --version — Display the gcov-tool version number (on the standard output), and exit without doing any further processing. ✨

🎀 merge

Merge two profile directories. Two directories walk into a bar, one profile walks out. 💅

  • -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.

🦋 rewrite

Read the specified profile directory and rewrite to a new directory. Glow-up arc for your profile. ✨

  • -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 as 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. Math girlies rise up. 👑

  • -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, 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 the gcc-12 era, dated 2022-03-19. Slay, go merge some profiles. 💅✨🎀

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