Variadic UNUSED function/macro

Question

A well-known and portable way to suppress C compiler warnings about unused variables is (see unused parameter warnings in C code):

#define UNUSED(x) (void)(x)
         


        

Answer 1

Based on these two posts Variadic macro to count number of arguments, and Overloading macros i made the following

#define UNUSED1(x) (void)(x)
#define UNUSED2(x,y) (void)(x),(void)(y)
#define UNUSED3(x,y,z) (void)(x),(void)(y),(void)(z)
#define UNUSED4(a,x,y,z) (void)(a),(void)(x),(void)(y),(void)(z)
#define UNUSED5(a,b,x,y,z) (void)(a),(void)(b),(void)(x),(void)(y),(void)(z)

#define VA_NUM_ARGS_IMPL(_1,_2,_3,_4,_5, N,...) N
#define VA_NUM_ARGS(...) VA_NUM_ARGS_IMPL(__VA_ARGS__, 5, 4, 3, 2, 1)

#define ALL_UNUSED_IMPL_(nargs) UNUSED ## nargs
#define ALL_UNUSED_IMPL(nargs) ALL_UNUSED_IMPL_(nargs)
#define ALL_UNUSED(...) ALL_UNUSED_IMPL( VA_NUM_ARGS(__VA_ARGS__))(__VA_ARGS__ )

what can be used as follows

 int main()
 {
    int a,b,c;
    long f,d;

    ALL_UNUSED(a,b,c,f,d);

    return 0;
  }

eclipse macro expansion gives :

  (void)(a),(void)(b),(void)(c),(void)(f),(void)(d)

compiled with gcc -Wall with no warnings

EDIT:

#define UNUSED1(z) (void)(z)
#define UNUSED2(y,z) UNUSED1(y),UNUSED1(z)
#define UNUSED3(x,y,z) UNUSED1(x),UNUSED2(y,z)
#define UNUSED4(b,x,y,z) UNUSED2(b,x),UNUSED2(y,z)
#define UNUSED5(a,b,x,y,z) UNUSED2(a,b),UNUSED3(x,y,z)

EDIT2

As for inline method you posted, a quick test

int a=0;
long f,d;

ALL_UNUSEDINLINE(a,f,&d);

gives ‘f’ is used uninitialized in this function [-Wuninitialized] warning. So here at least one use case which breaks generality of this aproach