fuzz: Exclude too expensive inputs in descriptor_parse targets #34317

1. 
   maflcko commented at 12:00 pm on January 16, 2026: member

   Accepting “expensive” fuzz inputs which have no real use-case is problematic, because it prevents the fuzz engine from spending time on the next useful fuzz input.

   For example, those will take several seconds (!) and the flamegraph shows that base58 encoding is the cause:

   0curl -fLO 'https://github.com/bitcoin-core/qa-assets/raw/b5ad78e070e4cf36beb415d7b490d948d70ba73f/fuzz_corpora/mocked_descriptor_parse/f5abf41608addcef3538da61d8096c2050235032'
   1curl -fLO 'https://github.com/bitcoin-core/qa-assets/raw/b5ad78e070e4cf36beb415d7b490d948d70ba73f/fuzz_corpora/descriptor_parse/78cb3175467f53b467b949883ee6072e92dbb267'
   2
   3FUZZ=mocked_descriptor_parse ./bld-cmake/bin/fuzz ./f5abf41608addcef3538da61d8096c2050235032
   4FUZZ=descriptor_parse ./bld-cmake/bin/fuzz ./78cb3175467f53b467b949883ee6072e92dbb267
   

   This will also break 32-bit fuzzing, see #34110 (comment).

   Fix all issues by checking for HasTooLargeLeafSize.

   Sorry for creating several pull requests to fix this class of issue, but I think this one should be the last one. :sweat_smile:

2. DrahtBot added the label Fuzzing on Jan 16, 2026
3. 
   DrahtBot commented at 12:00 pm on January 16, 2026: 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/34317.

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4. fuzz: Exclude too expensive inputs in descriptor_parse targets

   Also, fixup iwyu warnings in the util module.
   
   Also, fixup a typo.

   fa3fe1d7f8
5. maflcko force-pushed on Jan 16, 2026
6. DrahtBot added the label CI failed on Jan 16, 2026
7. DrahtBot removed the label CI failed on Jan 16, 2026
8. in src/test/fuzz/util/descriptor.cpp:15 in fa3fe1d7f8

    6@@ -7,12 +7,15 @@
    7 #include <key.h>
    8 #include <key_io.h>
    9 #include <pubkey.h>
   10+#include <span.h>
   11 #include <util/strencodings.h>
   12 
   13 #include <ranges>
   14 #include <stack>
   15+#include <vector>
   

   ---

   ---

   

   hebasto commented at 4:11 pm on January 16, 2026:

   https://github.com/bitcoin/bitcoin/actions/runs/21066056093/job/60583609633?pr=34317:

   0(/home/admin/actions-runner/_work/_temp/src/test/fuzz/util/descriptor.h has correct #includes/fwd-decls)
   1
   2(/home/admin/actions-runner/_work/_temp/src/test/fuzz/util/descriptor.cpp has correct #includes/fwd-decls)
   

   Mind appending src/test/fuzz/util/descriptor.cpp to the FILES_WITH_ENFORCED_IWYU variable in ci/test/03_test_script.sh?

   ---

   

   maflcko commented at 4:36 pm on January 16, 2026:

   This will create a conflict with other pulls, so I’ll leave this as-is for now.
9. 
   frankomosh commented at 5:23 am on January 19, 2026: contributor

   Code Review ACK fa3fe1d7f8d857112b8c5b1a991fe25b3ded9324

   Good refactor that effectively addresses the expensive input issue

10. fanquake requested review from dergoegge on Jan 20, 2026

Contributors
maflcko DrahtBot hebasto frankomosh

Review Requested
dergoegge

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Fuzzing