refactor: Add helper for Taproot control block size check #34139

1. 
   billymcbip commented at 5:24 pm on December 22, 2025: contributor

   Add a helper for the Taproot control block size check to improve readability and reduce repetition. We currently have three instances of this check.

   Build & unit tests succeed on my end.

2. refactor: Add helper for Taproot control block size check d7bbd8de23
3. DrahtBot added the label Refactoring on Dec 22, 2025
4. 
   DrahtBot commented at 5:24 pm on December 22, 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/34139.

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5. 
   rkrux commented at 12:41 pm on December 23, 2025: contributor

   Concept ~0 (leaning towards n-a-c-k) d7bbd8de23cdef0d844e359cf3e86b7980510cdb

   While this refactor does reduce repetition and also allows reusability in the signingprovider as well, I don’t think it’s worth the code churn imho.

   Let’s see what other reviewers have to say on this.

6. 
   billymcbip commented at 12:50 pm on December 23, 2025: contributor

   @rkrux thank you for your feedback. Could you have a look at #34142 as well? That’d be a fourth instance of this check.
7. test: Add unit tests for Taproot control block size check 2c53c4d342
8. in src/script/interpreter.cpp:1872 in d7bbd8de23 outdated

   1868@@ -1869,6 +1869,11 @@ static bool ExecuteWitnessScript(const std::span<const valtype>& stack_span, con
   1869     return true;
   1870 }
   1871 
   1872+bool VerifyTaprootControlBlockSize(std::span<const unsigned char> control)
   

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   janb84 commented at 11:34 am on December 24, 2025:

   With the introduction of this function I would expect that there also would be some additional tests

   ---

   

   billymcbip commented at 12:01 pm on December 24, 2025:

   Added! 2c53c4d3428518b22bd9f372ea70bd546bbd65c3

   I don’t want to commit a test case for max size because that would require a 8260-character string, but I did test that locally as well: 21031934357fc5f97a4dfa3c13ed9f3b77219d42

9. 
   rkrux commented at 8:51 am on December 26, 2025: contributor

   @rkrux thank you for your feedback. Could you have a look at #34142 as well? That’d be a fourth instance of this check.

   Both these PRs contain similar changes with minor differences, I was initially confused but later got the intent.

   Suggest to keep only 1 PR that contains all the changes, will be easier for the reviewers imho to get the whole context.

Contributors
billymcbip DrahtBot rkrux janb84

Labels
Refactoring