Variations
You can of course choose your own E type so long as it has standard layout
and is trivially copyable. You would declare that with CXX_DECLARE_RESULT(t_ident, t_decl, e_ident, e_decl)
,
refer to it with CXX_RESULT(t_ident, e_ident)
and need to do your own
decoding of errors from your E type. By using the _EC postfixed macros,
you are in fact using E =
struct cxx_error_code
{
int code;
void *category;
};… which is declared for you by result.h.
Outcome’s C support was designed assuming that you do not wish to penalise the performance
of C++ code calling these C-compatible C++ functions, but if you don’t care
about that, then always setting errno to any error in a result<T> is easily
implemented and thus the natural C use pattern becomes available:
extern size_t to_string(char *buffer, size_t bufferlen, int v);
...
size_t len = to_string(buffer, sizeof(buffer), v);
if(errno != 0)
...Implementing this via boilerplate generating script is straightforward, and is left as an exercise to the interested reader.