Why does converting char to wchar_t in my Unicode application result in undefined behavior?

How to Convert char to wchar_t for Unicode Integration

Problem:

Developers may encounter issues converting char to wchar_t in Unicode applications. The following code example illustrates a common error:

<code class="cpp">const wchar_t *GetWC(const char *c)
{
    const size_t cSize = strlen(c)+1;
    wchar_t wc[cSize];
    mbstowcs (wc, c, cSize);

    return wc;
}</code>

Answer:

The issue arises because wc is a local variable that is deallocated when the function returns. This results in undefined behavior. The correct approach is to allocate wc dynamically using new and ensure that the calling code deallocates the memory:

<code class="cpp">const wchar_t *GetWC(const char *c)
{
    const size_t cSize = strlen(c)+1;
    wchar_t* wc = new wchar_t[cSize];
    mbstowcs (wc, c, cSize);

    return wc;
}</code>

Note: The calling code must be responsible for deallocating the allocated memory to avoid memory leaks.

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