Widechar to Multibyte and Multibyte to Widechar in Windows

wtoa_atow.c

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <windows.h>

wchar_t *atow(char *str) {
	wchar_t *result;
	int length;

    if (str == NULL) return NULL;
	
	length = MultiByteToWideChar(CP_UTF8, 0, str, -1, NULL, 0);

	result = malloc((length + 1) * sizeof(wchar_t));
	if (result == NULL) return NULL;
	
	MultiByteToWideChar(CP_UTF8, 0, str, -1, result, length);
    result[length] = L'\0';
	
	return result;
}

char *wtoa(wchar_t *wstr) {
	char *result;
	size_t size;
	
	if (wstr == NULL) return NULL;

	size = WideCharToMultiByte(CP_UTF8, WC_NO_BEST_FIT_CHARS, wstr, -1, NULL, 0, NULL, NULL);
	if (size <= 0) return NULL;
	
	result = malloc(size + 1);
	if (result == NULL) return NULL;
	
	if (WideCharToMultiByte(CP_UTF8, WC_NO_BEST_FIT_CHARS, wstr, -1, result, size, NULL, NULL) <= 0) {
		free(result);
		return NULL;
	}
	
	result[size] = '\0';
	
	return result;
}

int main(void) {
	setlocale(LC_ALL, "");
	
	char *str = wtoa(L"Não é Âncora");
	wchar_t *wstr = atow(str);
	wprintf(L"(%ls)\n", wstr);
	return 0;
}