本文代码已在vs2017上验证。gbk转utf8容易出现中文乱码，有的时候在x86 32位编译环境下中文显示正常，但切换到x64 64位编译环境下会乱码。本文所示的代码在32位和64位编译环境下均不会出现乱码。使用例子见：。

#include <iostream>
#include <stdlib.h>
#include <string>
#include <string.h>
#include <windows.h>

using namespace std;

string GBK_2_UTF8(string gbkStr)
{
	string outUtf8 = "";
	int n = MultiByteToWideChar(CP_ACP, 0, gbkStr.c_str(), -1, NULL, 0);
	WCHAR *str1 = new WCHAR[n];
	MultiByteToWideChar(CP_ACP, 0, gbkStr.c_str(), -1, str1, n);
	n = WideCharToMultiByte(CP_UTF8, 0, str1, -1, NULL, 0, NULL, NULL);
	char *str2 = new char[n];
	WideCharToMultiByte(CP_UTF8, 0, str1, -1, str2, n, NULL, NULL);
	outUtf8 = str2;
	delete[]str1;
	str1 = NULL;
	delete[]str2;
	str2 = NULL;
	return outUtf8;
}

string UTF8_2_GBK(string utf8Str)
{
	string outGBK = "";
	int n = MultiByteToWideChar(CP_UTF8, 0, utf8Str.c_str(), -1, NULL, 0);
	WCHAR *str1 = new WCHAR[n];
	MultiByteToWideChar(CP_UTF8, 0, utf8Str.c_str(), -1, str1, n);
	n = WideCharToMultiByte(CP_ACP, 0, str1, -1, NULL, 0, NULL, NULL);
	char *str2 = new char[n];
	WideCharToMultiByte(CP_ACP, 0, str1, -1, str2, n, NULL, NULL);
	outGBK = str2;
	delete[] str1;
	str1 = NULL;
	delete[] str2;
	str2 = NULL;
	return outGBK;
}