mingw-w64-crt/stdio/_vscprintf.c

/**
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is part of the mingw-w64 runtime package.
 * No warranty is given; refer to the file DISCLAIMER.PD within this package.
 */
#include <windows.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

/* emulation of _vscprintf() via _vsnprintf() */
static int __cdecl emu__vscprintf(const char * __restrict__ format, va_list arglist)
{
    char *buffer, *new_buffer;
    size_t size;
    int ret = -1;

    /* if format is a null pointer, _vscprintf() returns -1 and sets errno to EINVAL */
    if (!format) {
        errno = EINVAL;
        return -1;
    }

    /* size for _vsnprintf() must be non-zero and buffer must have place for terminating null character */
    size = strlen(format) * 2 + 1;
    buffer = malloc(size);

    if (!buffer) {
        errno = ENOMEM;
        return -1;
    }

    /* if the number of characters to write is greater than size, _vsnprintf() returns -1 */
    while (size < SIZE_MAX/2 && (ret = _vsnprintf(buffer, size, format, arglist)) < 0) {
        /* in this case try with larger buffer */
        size *= 2;
        new_buffer = realloc(buffer, size);
        if (!new_buffer)
            break;
        buffer = new_buffer;
    }

    free(buffer);

    if (ret < 0) {
        errno = ENOMEM;
        return -1;
    }

    return ret;
}

#define RETT int
#define FUNC _vscprintf
#define ARGS const char * restrict format, va_list arglist
#define CALL format, arglist
#include "msvcrt_or_emu_glue.h"