source: bootcd/isolinux/syslinux-6.03/com32/lib/vasprintf.c

/*
 * vasprintf.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

int vasprintf(char **bufp, const char *format, va_list ap)
{
    va_list ap1;
    int bytes;
    char *p;

    va_copy(ap1, ap);

    bytes = vsnprintf(NULL, 0, format, ap1) + 1;
    va_end(ap1);

    *bufp = p = malloc(bytes);
    if (!p)
        return -1;

    return vsnprintf(p, bytes, format, ap);
}