xasprintf.c

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#ifndef _GNU_SOURCE
 
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
 
/*  Multiplatform implementation of asprintf() from:
    https://stackoverflow.com/questions/40159892/using-asprintf-on-windows
    define _GNU_SOURCE to use the GNU asprintf extension instead this one.
*/
 
 
#include "xasprintf.h"
 
int _vscprintf_so(const char * format, va_list pargs) {
    int retval;
    va_list argcopy;
    va_copy(argcopy, pargs);
    retval = vsnprintf(NULL, 0, format, argcopy);
    va_end(argcopy);
    return retval;
}
 
int vasprintf(char **strp, const char *fmt, va_list ap) {
    int len = _vscprintf_so(fmt, ap);
    if (len == -1) return -1;
    char *str = malloc((size_t) len + 1);
    if (!str) return -1;
    int r = vsnprintf(str, len + 1, fmt, ap);
    if (r == -1) return free(str), -1;
    *strp = str;
    return r;
}
 
int asprintf(char *strp[], const char *fmt, ...) {
    va_list ap;
    va_start(ap, fmt);
    int r = vasprintf(strp, fmt, ap);
    va_end(ap);
    return r;
}
 
#endif // !_GNU_SOURCE