I am attempting to create bindings from the C library libsecp256k1 into Scheme (the guile implementation) but I am guessing my question applies to other target languages. Say I want to export the function secp256k1_context_create: this function expects an int as an argument which can be one of the macros SECP256K1_CONTEXT_VERIFY, SECP256K1_CONTEXT_SIGN or SECP256K1_CONTEXT_NONE. Now these macros are part of the C API, but as far I can tell there is no way to access their values from the shared library:
$ cd /usr/local/lib
$ nm libsecp256k1.so
... (no names relating to flag values)
So it seems I need to define my own values for the flags in the target language:
(define %context-verify 257)
(define %context-sign 513)
(define %context-none 1)
However, in doing so, I am hard-coding implementation details, which means my target language library could break despite the C API being stable (actually I am not sure whether this constitute an API change if existing object code needs to be recompiled, ABI change?). Could anyone let me know whether I have missed anything, or whether there is a better approach to this problem?
