Unexpected results with wchar_t and c_str string conversion

Question

Based on this answer to a related question, I tried to write a method that converts a standard string to a wide string, which I can then convert into a wchar_t*.

Why aren't the two different ways of creating the wchar_t* equivalent? (I've shown the values that my debugger gives me).

TEST_METHOD(TestingAssertsWithGetWideString)
{
   std::wstring wString1 = GetWideString("me");
   const wchar_t* wchar1 = wString1.c_str(); // wchar1 = "me"
   const wchar_t* wchar2 = GetWideString("me").c_str(); // wchar2 = "ﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮ@" (Why?!)
}

where GetWideString is defined as follows:

inline const std::wstring GetWideString(const std::string &str)
{
   std::wstring wstr;
   wstr.assign(str.begin(), str.end());

   return wstr;
};

Note: the following doesn't work either.

const wchar_t* wchar2 = GetWChar("me");

const wchar_t *GetWChar(const std::string &str)
{
   std::wstring wstr;
   wstr.assign(str.begin(), str.end());

   return wstr.c_str();
};

Answer 1

Each time you call GetWideString(), you are creating a new std::wstring, which has a newly allocated memory buffer. You are comparing pointers to different memory blocks (assuming Assert::AreEqual() is simply comparing the pointers themselves and not the contents of the memory blocks that are being pointed at).

Update: const wchar_t* wchar2 = GetWideString("me").c_str(); does not work because GetWideString() returns a temporary std::wstring that goes out of scope and gets freed as soon as the statement is finished. Thus you are obtaining a pointer to a temporary memory block, and then leaving that pointer dangling when that memory gets freed before you can use the pointer for anything.

Also, const wchar_t* wchar2 = GetWChar("me"); should not compile. GetWChar() returns a std::wstring, which does not implement an implicit conversion to wchar_t*. You have to use the c_str() method to get a wchar_t* from a std::wstring.