CODEWITHSUNDEEP
c++c-preprocessor
Superlokkus
Superlokkus

Reputation: 5059

Define name i.e. macro as nothing

While using a 3rd party shared library i.e. DLL, I have to define the functions usable by their symbol names. So I have to declare some function types.

But the function definition involves a calling convention, in my case __cdecl.

So, naturally, this calling convention is only applicable to the MSVC compiler but I still want to compile my portable API abstraction code, which uses boost::dll with linux, even though I can not execute it on my development linux machine, so I can still check the compile time stuff.

So my idea was to define the __cdecl name to something as nothing or a white space, a NOP if you will, with the pre-processor, but I am not able to do that:

#if !BOOST_OS_WINDOWS
#define  __cdecl ( ) /* error, how can I define __cdecl as 'nothing" here? */
#endif

#include <boost/dll/import.hpp>
boost::dll::shared_library lib;

unsigned long device_count(char* pid) {
    typedef unsigned long(__cdecl func_sig)(char *pvid_id);
    return lib.get<func_sig>("DLL_Symbol")(pid);
}

Upvotes: 3

Views: 263

Answers (1)

Quentin
Quentin

Reputation: 63144

#define __cdecl

Couldn't be simpler! Or better, to limit the spreading of implementation-reserved identifiers:

#if BOOST_OS_WINDOWS
    #define YOURLIB_CDECL __cdecl
#else
    #define YOURLIB_CDECL /* nothing */
#endif

Upvotes: 3

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