Question

When I send text to my DLL and receive it as char*, something strange happens; if the text is less than 13 characters or greater than 77 characters the text returned is rubbish!

Here is my code:-

//(1) DLL function:

char* __stdcall ApplyArabicMapping( char* input)
{
    // 1-Conver char* to string
    std::string inputString = input;

    // 2-Calling our function
    string encodedStr = Encoding::arabicHandling(inputString);

    // 3-Convert from String to char*
    char* returnStr = (char*)encodedStr.c_str();
    return (returnStr);
}

//(2) Calling from C++ console application:

char* inputStr = "Some text";

char* resutls = ApplyArabicMapping(inputStr);

Answer 1

A dangling pointer is being returned as encodedStr is being destructed when ApplyArabicMapping() returns, resulting in undefined behaviour.

To correct, either return a std::string if possible or make a copy of the char* buffer using new and return it: the caller must delete[] this when no longer required:

char* returnStr = new char[encodedStr.length() + 1];
std::copy(encodedStr.begin(), encodedStr.end(), returnStr);
*(returnStr + encodedStr.length()) = 0; // null terminate.