In more recent modules (ellswift, musig and silentpayments), the following pattern of serializing a non-infinity group element to a 33-bytes compressed public key appears repeatedly:
0 size_t ser_size = 33;
1 int ser_ret;
2 .....
3 ser_ret = secp256k1_eckey_pubkey_serialize(ge, out33, &ser_size, 1);
4#ifdef VERIFY
5 VERIFY_CHECK(ser_ret && ser_size == 33);
6#else
7 (void)ser_ret;
8#endif
One could deduplicate these instances by a new function, as suggested by @w0xlt in the latest silentpayments module PR, see #1765#pullrequestreview-3462461331. This could simplify the code in the modules quite a bit (less LOC, less variables, less pre-processor blocks). Demo branch: https://github.com/theStack/secp256k1/commit/e02365188ac8bb5129dc36c817fb465dfa5f7b76. It seems a reasonable idea to me, but not sure about the right naming of the function and where to put it. Also, one drawback might be that if the VERIFY_CHECK fails, it’s a bit harder to find out the cause if it fails in a helper rather than directly in the module code (not sure if we care about that?). Opening this as an issue first to see if there is conceptual support.
