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

int vasprintf(char **ret, const char *fmt, va_list ap)
{
char *buf;
int len;
size_t buflen;
va_list ap2;

#ifdef _MSC_VER
ap2 = ap;
#else
va_copy(ap2, ap);
#endif

len = vsnprintf(NULL, 0, fmt, ap2);

if (len > 0 && (buf = malloc((buflen = (size_t) (len + 1)))) != NULL) {
len = vsnprintf(buf, buflen, fmt, ap);
*ret = buf;
} else {
*ret = NULL;
len = -1;
}

va_end(ap2);
return len;
}