为什么获取环境变量getenv小心有坑

// getenv函数所需头文件
#include <cstdlib>
#include <iostream>
// _wgetenv函数所需头文件
#include <cwchar>
#include <string>
// GetEnvironmentVariable函数所需头文件
#include <windows.h>

extern "C" {
    __declspec(dllexport) const char* get() {
        const char* path_env = std::getenv("PATH_TEST");
        return path_env;
    }
}

extern "C" {
    __declspec(dllexport) const char* get_wide() {
        wchar_t* wpath_env = _wgetenv(L"PATH_TEST");
        if (wpath_env != nullptr) {
            static std::string path_env;
            path_env.assign(wpath_env, wpath_env + wcslen(wpath_env));
            return path_env.c_str();
        }
        return nullptr;
    }
}

extern "C" {
    __declspec(dllexport) const char* get_winapi() {
        static char buffer[4096];
        DWORD result = GetEnvironmentVariable("PATH_TEST", buffer, sizeof(buffer));
        if (result > 0 && result < sizeof(buffer)) {
            return buffer;
        }
        return nullptr;
    }
}

using System;
using System.Runtime.InteropServices;

class Program
{
    static void Main(string[] args)
    {
        string pathVariable = Environment.GetEnvironmentVariable("PATH_TEST");
        pathVariable += @"C:\Your\New\Path**********";
        Environment.SetEnvironmentVariable("PATH_TEST", pathVariable);
        Console.WriteLine("C# PATH environment variable:");
        Console.WriteLine(Environment.GetEnvironmentVariable("PATH_TEST"));
        Console.WriteLine("C++ PATH environment variable:");
        Print();
    }
    [DllImport("TestC.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern IntPtr get();
    static void Print()
    {
        var s = get();
        string result = Marshal.PtrToStringAnsi(s);
        Console.WriteLine(result);
    }

}

@echo off

if exist build (
    echo Build folder already exists. Deleting...
    rmdir /s /q build
)

echo Build folder create..
mkdir build

echo Running CMake configuration...
cmake -B build -DCMAKE_CXX_COMPILER=g++ -G Ninja

echo Building the project...
cmake --build build

echo Build completed.

/* glibc/stdlib/getenv.c下的代码 */

#include <stdlib.h>
#include <string.h>
#include <unistd.h>

char *
getenv (const char *name)
{
  if (__environ == NULL || name[0] == '\0')
    return NULL;

  size_t len = strlen (name);
  for (char **ep = __environ; *ep != NULL; ++ep)
    {
      if (name[0] == (*ep)[0]
	  && strncmp (name, *ep, len) == 0 && (*ep)[len] == '=')
	return *ep + len + 1;
    }

  return NULL;
}
libc_hidden_def (getenv)