Interfacing with C libs: weeding through C/C++ macros and such in header files

[Alex]

On Sunday, 13 January 2019 at 22:40:57 UTC, Alec Stewart wrote:
> Example without code; for some reason a macro is defined for 
> the stdlib functions `malloc`, `realloc`, and `free`. Maybe 
> it's just because I don't have any pro experience with C or 
> C++, but that seems a bit excessive. Or I could just be dumb.
>

These three are members of the standard library in D.
https://dlang.org/phobos/core_memory.html

> Example with code (because I need help figuring out how whether 
> I even need this or not):
>
>     #ifndef RS_API
>     #ifdef RS_NOINLINE
>     /* GCC version 3.1 required for the no inline attribute. */
>     #if RS_GCC_VERSION > 30100
>     #define RS_API static __attribute__((noinline))
>     #elif defined(_MSC_VER)
>     #define RS_API static __declspec(noinline)
>     #else
>     #define RS_API static
>     #endif
>     #elif RS_C99
>     #define RS_API static inline
>     #elif defined(__GNUC__)
>     #define RS_API static __inline__
>     #elif defined(_MSC_VER)
>     #define RS_API static __forceinline
>     #else
>     #define RS_API static
>     #endif
>     #endif
>
> I understand what it's doing, but do I really any of this with 
> D? And then there's this inline function
>
>     #define RS_DATA_SIZE(f, s, input)
>           \
> 	    do {
>    \
> 		    if (rs_is_heap(input))                                  \
> 			    f(s, input->heap.buffer, rs_heap_len(input));   \
> 		    else                                                    \
> 			    f(s, input->stack.buffer, rs_stack_len(input)); \
> 	    } while (0)
>
> so yea. There's a little over 300 lines of preprocessor stuff. 
> My question is how you all determine what to carry over from C 
> libs in terms of preprocessor stuff. I imagine most useful 
> values everyone just makes an enum for, and structs and unions 
> are kept.
>
> Thanks for any help you give!

At first, I would suggest to try out some automatic converters, 
which are written by the community:
https://wiki.dlang.org/Bindings#Binding_generators
especially dstep and dpp

I had some ambivalent experience with the procedure of converting 
C --> D, but there is C code out there, which behaves very well 
in this respect... So, generally, I pursued the tactics of
automatic conversion
trying to compile
rewriting missing parts.

Also, if there is a possibility to compile the C/C++ library, you 
could provide the interface only to the functions you need. Then, 
you reuse the existent code directly and interface the library by 
declaring the interfaces as extern in your D sources.
https://dlang.org/spec/attribute.html#linkage