Type overloading macro | 易学教程

问题

I have a bunch of printf debug helper macros and it would be pretty cool to have to not specify the type, is there anything you can do to allow something like macro overloading in c(can be gcc specific if its available in gcc 4.3). I thought maybe typeof but apparently that doesn't work.

example macro(I also have some ascii terminal color stuff that I can't remember of the top of my head)

#ifdef _DEBUG
#define DPRINT_INT(x) printf("int %s is equal to %i at line %i",#x,x,__LINE__);
.
.
.
#else
#define DPRINT_INT(x)
.
.
.
#endif

回答1:

Try this; it uses gcc's __builtin methods, and automatically determines the type for you, as best it can, and makes for an easy DEBUG macro where you don't have to specify the type. Of course, you can compare typeof (x) to float, etc. etc.

#define DEBUG(x)                                                 \
  ({                                                             \
    if (__builtin_types_compatible_p (typeof (x), int))          \
        fprintf(stderr,"%d\n",x);                                \
    else if (__builtin_types_compatible_p (typeof (x), char))    \
        fprintf(stderr,"%c\n",x);                                \
    else if (__builtin_types_compatible_p (typeof (x), char[]))  \
        fprintf(stderr,"%s\n",x);                                \
    else                                                         \
        fprintf(stderr,"unknown type\n");                        \

  })

回答2:

How about the following macro? It still requires you to pick the print format but you won't have to redefine all possible cases and it works on MSVC as well:

#define DPRINT(t,v) printf("The variable '%s' is equal to '%" ## #t ## "' on line %d.\n",#v,v, __LINE__)

To use it:

int var = 5;
const char *str = "test";
DPRINT(i,var);
DPRINT(s,str);

回答3:

I think you can give a try with following code:

#define DPRINT(fmt) do{ \
            my_printf fmt ; \
        } while(0)

my_printf( const char* szFormat, ... )
{
    char szDbgText[100];

    va_start(args, szFormat);
    vsnprintf(&szDbgText,99,szFormat,args);
    va_end(args);

    fprintf( stderr, "%s", szDbgText );
}
// usage
func( )
{
    int a = 5;
    char *ptr = "hello";

    DPRINT( ("a = %d, ptr = %s\n", a, ptr) );
}

Note: DPRINT usage takes dual parentheses here.

来源：https://stackoverflow.com/questions/5633608/type-overloading-macro

标签

macros

overloading

tostring

printf-debugging