Creating a proxy function to fprintf in an unobtrusive way?

Question

I'd like to create a proxy to fprintf, like so:

void raise_exception(char *filename, int line, char *format_string, ...) {
    fprintf(stderr, "Exception in `%s`:%d!\n", filename, line);
    fprintf(stderr, format_string, ...);
    exit(EXIT_FAILURE);
}

But what do I put in the place of the second ellipsis? Is it at all possible?

I'd like to simplify it even a bit more like so:

#define RAISE(...) raise_exception(__FILE__, __LINE__, ...)

But I don't think this would work either.

Any ideas? Thanks!

UPDATE

Straight from Wikipedia:

Variable-argument macros were introduced in the ISO/IEC 9899:1999 (C99)

So the define that would do it should look like so:

#define RAISE(...) raise_exception(__FILE__, __LINE__, __VA_ARGS__)

I suggest making the macro: `#define RAISE(fmt, ...) raise_exception(__FILE__, __LINE__, fmt, __VA_ARGS__)` so that people can't try to pass no arguments to RAISE. — Jonathan Leffler, Jun 03 '11 at 17:51

score 6 · Accepted Answer · answered Jun 03 '11 at 16:22

#include <stdarg.h>
void raise_exception(char *filename, int line, char *format_string, ...)
{
    va_list args;
    fprintf(stderr, "Exception in `%s`:%d!\n", filename, line);
    va_start(args, format_string);
    vfprintf(stderr, format_string, args);
    va_end(args);
    exit(EXIT_FAILURE);
}

score 1 · Answer 2 · answered Jun 03 '11 at 16:22

1

Use vfprintf instead.

answered Jun 03 '11 at 16:22

Oliver Charlesworth

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score 1 · Answer 3 · edited May 23 '17 at 12:23

1

Please see this question:

Passing variable number of arguments around

Your exact example -- of wrapping printf -- is used as an example in the discussion here:

http://www.swig.org/Doc1.3/Varargs.html

edited May 23 '17 at 12:23

Community

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answered Jun 03 '11 at 16:23

occulus

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Creating a proxy function to fprintf in an unobtrusive way?

UPDATE

3 Answers3