fuzz: doc: add info about afl-system-config for macOS #32175

1. 
   brunoerg commented at 4:17 pm on March 31, 2025: contributor

   afl-system-config adjusts the shared memory segment size limits and configures kernel parameters for better fuzzing performance. Since macOS has more conservative values on shared memory, it’s necessary to run afl-system-config, or manually adjust the values to fuzz with AFL++.

   e.g.:

   0kern.sysv.shmmax: 524288000
   1kern.sysv.shmmin: 1
   2kern.sysv.shmseg: 48
   3kern.sysv.shmall: 131072000
   

2. 
   DrahtBot commented at 4:17 pm on March 31, 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/32175.

   Reviews

   See the guideline for information on the review process.

   Type	Reviewers
   ACK	janb84, w0xlt

   If your review is incorrectly listed, please react with 👎 to this comment and the bot will ignore it on the next update.

3. DrahtBot added the label Tests on Mar 31, 2025
4. in doc/fuzzing.md:190 in 66572c2745 outdated

   186@@ -187,6 +187,8 @@ $ cmake -B build_fuzz \
   187 $ cmake --build build_fuzz
   188 # For macOS you may need to ignore x86 compilation checks when running "cmake --build". If so,
   189 # try compiling using: AFL_NO_X86=1 cmake --build build_fuzz
   190+# Also, it might be required to run afl-system-config to adjust the shared
   

   ---

   ---

   

   janb84 commented at 5:59 pm on April 14, 2025:

   0# Also, it might be required to run "afl-system-config" to adjust the shared
   

   Small nit, to keep it in the same style as line 188

   ---

   

   brunoerg commented at 5:56 pm on April 28, 2025:

   Done. Thanks.
5. 
   janb84 commented at 6:02 pm on April 14, 2025: contributor

   Concept ACK 66572c2

   Small style NIT, to keep the comment in the same style as 2 lines before. Not blocking.

   Overall small addition to the documentation, provides extra valuable information, looks good to me.

6. brunoerg force-pushed on Apr 28, 2025
7. 
   brunoerg commented at 5:56 pm on April 28, 2025: contributor

   Pushed 66572c27454e1464173dc318d62fdfc11d4b7832..6e026606f368d8d1139b266c382076685e76d0b2 to address #32175 (review)
8. 
   janb84 commented at 6:04 pm on April 28, 2025: contributor

   re ACK 6e02660

   Changes sinds last ACK:

   • Minor style change in comments to align with rest of comment style.
9. DrahtBot added the label CI failed on Apr 29, 2025
10. fuzz: doc: add info about `afl-system-config` for macOS 61ea5f348d
11. brunoerg force-pushed on Apr 29, 2025
12. DrahtBot removed the label CI failed on Apr 29, 2025
13. 
    janb84 commented at 6:21 pm on April 29, 2025: contributor

    reACK 61ea5f3

    Changes since last ACK:

    • none, CI related push
14. 
    w0xlt commented at 11:13 pm on May 8, 2025: contributor

    ACK https://github.com/bitcoin/bitcoin/pull/32175/commits/61ea5f348da71b886807c0492587835dd7e57499

    Good clarification.

Contributors
brunoerg DrahtBot janb84 w0xlt

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