c99_printf_hacks.c

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/*
 * PROJECT:     ReactOS SDK
 * LICENSE:     MIT (https://spdx.org/licenses/MIT)
 * PURPOSE:     C99 printf-family shims for llvm-mingw runtime libraries
 * COPYRIGHT:   Copyright 2026 Ahmed Arif <arif.ing@outlook.com>
 */
 
#include <stdio.h>
#include <stdarg.h>
 
/* llvm-mingw's libc++ needs the C99 vsnprintf/snprintf contract, which msvcrt's _vsnprintf (aliased onto
 * these names by the crt headers) does not follow: undo the mapping and bridge over _vsnprintf/_vscprintf */
#undef vsnprintf
#undef snprintf
 
int vsnprintf(char *buffer, size_t count, const char *format, va_list argptr)
{
    va_list ap;
    int result;
 
    va_copy(ap, argptr);
    result = _vsnprintf(buffer, count, format, ap);
    va_end(ap);
 
    if (result >= 0 && (size_t)result < count)
        return result;
 
    /* Truncated: terminate and return the would-be length */
    if (count != 0)
        buffer[count - 1] = '\0';
 
    va_copy(ap, argptr);
    result = _vscprintf(format, ap);
    va_end(ap);
 
    return result;
}
 
int snprintf(char *buffer, size_t count, const char *format, ...)
{
    va_list argptr;
    int result;
 
    va_start(argptr, format);
    result = vsnprintf(buffer, count, format, argptr);
    va_end(argptr);
 
    return result;
}