c++ - 为什么这种理论上跨平台的代码不会改变 Windows 上的环境变量？

Question

所以我尝试下一个代码:

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <sstream>
#include <boost/filesystem/v3/path.hpp>
#include <boost/filesystem/v3/operations.hpp>
#ifdef WIN
#include <Windows.h>
#endif

void setEnviromentVariable(std::string name, boost::filesystem::path value)
{
    if ( getenv (name.c_str())==NULL)
    {
        std::cout << "Hit ENTER to restart application in order to agree with the next terms of use: do not eat my bytes!)" << std::endl;
        std::stringstream VAR;
        VAR << name<< "=" << value.native().c_str();
           #ifdef WIN
        std::stringstream VAL;
        VAL << value.native().c_str();
        if( !SetEnvironmentVariable(TEXT(name.c_str()), TEXT(VAL.str().c_str()))) 
        {
            printf("SetEnvironmentVariable failed (%d)\n", GetLastError()); 
        }
          #else
        setenv(VAR.str().c_str());
          #endif
        std::cin.get();

    }

}
int main(int argc, char *argv[])
{
        boost::filesystem::path full_path( boost::filesystem::current_path() / "assets/" );
        setEnviromentVariable("TCL_LIBRARY", full_path);
}

我的代码有什么问题？为什么它不设置任何环境变量，为什么它不显示任何错误？ ( WIN code is based on this. )

Answer 1

putenv() 将指定的字符串指针放在环境 vector 中；它不会复制字符串值。

The string pointed to by string becomes part of the environment. A program should not alter or free the string, and should not use stack or other transient string variables as arguments to putenv().

因此当 VAR 超出范围时，环境包含一个垃圾指针并且尝试访问它会出现段错误或返回垃圾。