ecmult: Use size_t for array indices #1794

1. 
   real-or-random commented at 10:43 am on January 7, 2026: contributor

   I don’t think the current code is incorrect, but using size_t improves readability because the type makes it clear that we’re dealing with array indices.

   Also, making the result of the ECMULT_TABLE_SIZE macro (hopefully) a size_t fixes a compiler warning on MSVC, see #1791.

2. real-or-random added the label tweak/refactor on Jan 7, 2026
3. ecmult: Use size_t for array indices into tables bb1d199de5
4. ecmult: Use size_t for array indices in _odd_multiplies_table 47eb70959a
5. real-or-random force-pushed on Jan 7, 2026
6. 
   hebasto commented at 11:58 am on January 7, 2026: member

   Concept ACK.

   I came to the same idea while working on #1791, but left it for later :)

7. hebasto approved
8. 
   hebasto commented at 12:48 pm on January 7, 2026: member

   ACK 9e7aede41eaf5dd6f4da7e233bc90982476f325e, I have reviewed the code and it looks OK.

   However, there are still more cases to address:

   • size_t i in: https://github.com/bitcoin-core/secp256k1/blob/2d9137ce9d7e576bfada2859292ecaa0887a6b8c/src/ecmult_impl.h#L339-L348
   • size_t m in: https://github.com/bitcoin-core/secp256k1/blob/2d9137ce9d7e576bfada2859292ecaa0887a6b8c/src/ecmult_const_impl.h#L93-L98
   • size_t i in: https://github.com/bitcoin-core/secp256k1/blob/2d9137ce9d7e576bfada2859292ecaa0887a6b8c/src/ecmult_const_impl.h#L228-L230

   Also, making the result of the ECMULT_TABLE_SIZE macro (hopefully) a size_t fixes a compiler warning on MSVC, see #1791.

   It does.

9. real-or-random force-pushed on Jan 7, 2026
10. 
    real-or-random commented at 2:22 pm on January 7, 2026: contributor

    • size_t i in: https://github.com/bitcoin-core/secp256k1/blob/2d9137ce9d7e576bfada2859292ecaa0887a6b8c/src/ecmult_impl.h#L339-L348

    I think there’s no perfect solution here, but fixing this one will open up the entire business of cleaning up types in secp256k1_ecmult_wnaf (see #1795), and I think this should be a separate PR.

    The same is true for the stuff in ecmult_gen; I think this could be a separate PR.

11. hebasto approved
12. 
    hebasto commented at 2:48 pm on January 7, 2026: member

    re-ACK 47eb70959a91bbfa10dc209e8ccbe7350f5b9b04.

Contributors
real-or-random hebasto

Labels
tweak/refactor