doc: reference fuzz coverage steps in quick-start #33536

frankomosh commented at 3:57 PM on October 3, 2025: contributor

Adds a single comment in the libFuzzer quick-start that links to the Developer Notes coverage section. No build flags are changed or shown.

DrahtBot added the label Docs on Oct 3, 2025

DrahtBot commented at 3:57 PM on October 3, 2025: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33536.

Reviews

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Type	Reviewers
ACK	janb84, dergoegge
Concept ACK	marcofleon

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frankomosh marked this as ready for review on Oct 3, 2025

janb84 commented at 9:47 AM on October 6, 2025: contributor

NACK Developer notes already has an extensive section on generating coverage. Maintaining the same documentation in 2 places is not ideal.

in doc/fuzzing.md:27 in 32c0e56c0a

  20 | @@ -21,6 +21,15 @@ See [further](#run-without-sanitizers-for-increased-throughput) for more informa
  21 |  There is also a runner script to execute all fuzz targets. Refer to
  22 |  `./build_fuzz/test/fuzz/test_runner.py --help` for more details.
  23 |  
  24 | +If you also want source-based coverage reports, append the instrumentation flags to `cmake --preset=libfuzzer`:
  25 | +
  26 | +```sh
  27 | +$ cmake --preset=libfuzzer \

maflcko commented at 9:54 AM on October 6, 2025:

not sure about recommending libfuzzer here. It has issues properly counting runs, so coverage will be off. See also https://github.com/bitcoin/bitcoin/blob/a33bd767a37dccf39a094d03c2f62ea81633410f/contrib/devtools/deterministic-fuzz-coverage/src/main.rs#L111-L115

frankomosh commented at 10:33 AM on October 6, 2025:

thanks. wasn't aware of the run counting issues with LibFuzzer.

So I guess the best approach is to build without the fuzzer sanitizer ?

frankomosh commented at 10:34 AM on October 6, 2025: contributor

NACK Developer notes already has an extensive section on generating coverage. Maintaining the same documentation in 2 places is not ideal.

ok . Would you atleast like to see a reference to the developer notes in this section(assume for someone who lands here first)?

janb84 commented at 12:03 PM on October 6, 2025: contributor

NACK Developer notes already has an extensive section on generating coverage. Maintaining the same documentation in 2 places is not ideal.

ok . Would you atleast like to see a reference to the developer notes in this section(assume for someone who lands here first)?

That would be better, imho (although the correct way would be to first read the contributing guide as a developer), but i can understand that one interested in fuzzing would only read the fuzzing readme before the contributing.md.

frankomosh force-pushed on Oct 8, 2025

fanquake commented at 1:48 PM on October 30, 2025: member

@frankomosh the PR description needs updating to reflect the current change?

cc @dergoegge @marcofleon

frankomosh renamed this:
~~doc: add coverage instrumentation hint to libFuzzer quickstart~~
doc: reference fuzz coverage steps in quick-start
on Oct 30, 2025

frankomosh commented at 6:11 PM on October 30, 2025: contributor

@frankomosh the PR description needs updating to reflect the current change?

cc @dergoegge @marcofleon

yeah indeed

in doc/fuzzing.md:24 in df1815e319

  20 | @@ -21,6 +21,8 @@ See [further](#run-without-sanitizers-for-increased-throughput) for more informa
  21 |  There is also a runner script to execute all fuzz targets. Refer to
  22 |  `./build_fuzz/test/fuzz/test_runner.py --help` for more details.
  23 |  
  24 | +For source-based `coverage reports`, see [Developer notes](https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#compiling-for-fuzz-coverage).

dergoegge commented at 3:35 PM on November 7, 2025:

nit:

For source-based `coverage reports`, see [developer notes](/doc/developer-notes.md#compiling-for-fuzz-coverage).

marcofleon commented at 6:21 PM on November 7, 2025:

nit: Not sure if "coverage reports" needs the backticks here?

frankomosh commented at 3:59 AM on November 10, 2025:

done. Thanks

frankomosh commented at 4:01 AM on November 10, 2025:

I don't think they are super helpful. I just removed them in the new commit.

dergoegge commented at 3:38 PM on November 7, 2025: member

Concept ACK - Seems reasonable to mention this in the actual fuzzing docs.

marcofleon commented at 6:24 PM on November 7, 2025: contributor

Concept ACK

doc: mention coverage build in quickstart section

Points a reader to Developer Notes which explains to compile with llvm source based coverage instrumentation

dee7eec643

frankomosh force-pushed on Nov 10, 2025

janb84 commented at 9:49 AM on November 10, 2025: contributor

ACK dee7eec64389aa48daff6f7f3ecbd931af72050a

The author removed the duplicate and redundant code coverage instructions which made me disagree with this PR. The author now only references that there are instructions on generating code coverage for fuzzing elsewhere in the documentation, which seems to me as a reasonable thing and good addition.

Thank you for changing this.

DrahtBot requested review from dergoegge on Nov 10, 2025

DrahtBot requested review from marcofleon on Nov 10, 2025

dergoegge approved

dergoegge commented at 10:11 AM on November 10, 2025: member

ACK dee7eec64389aa48daff6f7f3ecbd931af72050a

fanquake merged this on Nov 10, 2025

fanquake closed this on Nov 10, 2025

frankomosh deleted the branch on Nov 10, 2025

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