#define macro for debug printing in C?

Question

Trying to create a macro which can be used for print debug messages when DEBUG is defined, like the following pseudo code:

#define DEBUG 1
#define debug_prin         


        

Answer 1

My favourite of the below is var_dump, which when called as:

var_dump("%d", count);

produces output like:

patch.c:150:main(): count = 0

Credit to @"Jonathan Leffler". All are C89-happy:

Code

#define DEBUG 1
#include 
#include 
void debug_vprintf(const char *fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
}

/* Call as: (DOUBLE PARENTHESES ARE MANDATORY) */
/* var_debug(("outfd = %d, somefailed = %d\n", outfd, somefailed)); */
#define var_debug(x) do { if (DEBUG) { debug_vprintf ("%s:%d:%s(): ", \
    __FILE__,  __LINE__, __func__); debug_vprintf x; }} while (0)

/* var_dump("%s" variable_name); */
#define var_dump(fmt, var) do { if (DEBUG) { debug_vprintf ("%s:%d:%s(): ", \
    __FILE__,  __LINE__, __func__); debug_vprintf ("%s = " fmt, #var, var); }} while (0)

#define DEBUG_HERE do { if (DEBUG) { debug_vprintf ("%s:%d:%s(): HERE\n", \
    __FILE__,  __LINE__, __func__); }} while (0)