C++ Macros w/Variable Arguments

[twain]

I would like to create a macro (#define xxx(x,x) etc.) that will accept a varable number of arguments. I then want to send the variable number of arguments to a printf/FormatMessage style code. Can I do this in a macro? It's use would be:

#define SENDLOG(x,...) SendLog(x, __LINE__, __FILE__, ...)

Doesn't work. Anyone have any tricks?

Shawn Wildermuth
NetSuite Development Corporation

[Torkel]

I would write a function for it

[Jerry Coffin]

There are a couple ways of handling this. First of all, you can write a function instead of a macro. Since this sort of thing is often done for debugging, you usually use a pair of functions, one of which is a nop, and choose between them based on whether something is defined or not.

Although it's a little ugly, you can also get a macro to treat a number of things as a single argument by enclosing them in parentheses. For example, the following has been tested and runs:

#include <stdio.h>

#define SENDLOG(fmt, args) \
fprintf(stderr, "%d %s: " fmt, __LINE__, __FILE__, args)

// ...

int main() {

extern int errno;

char errname[20] ="A mock error string";

SENDLOG("%d %s", (errno, errname));
return 0;
}


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