[jjore]

A fairly commonsensical approach is to just require all extension authors to annotate their code properly. At some basic level, this happens with Perl with its oft-maligned DSL for generating C code that happens to do all the right declarations. You might then end up writing your code using more macros. It's certainly not pretty but it is sound.

A plausible rewrite of that function in an XS for ruby would leave the function declaration and wrapper code up to your equivalent of xsubpp to execute your DSL and transform the wrapped code to fully functional C. If you build a C using extension from Perl, you'll find an XS file like http://cpansearch.perl.org/src/SIMON/Devel-Pointer-1.00/Poin... which during the `perl Makefile.PL && make` step is transformed via `xsubpp Pointer.xs > Pointer.c` and then compiled as normal C.