Thread: Macro Question - HRESULTS and function names

> if (hr == E_FAIL)MessageBoxW(NULL, L#x, L"Function Failed", 0);

Stringification - The C Preprocessor

Essentially, it takes whatever the string of characters is for parameter x, and slaps double quotes around it to make it a string.


> and I also don't know why the macro has the single backslashes \ in it for each line.
Because #defines need to be a single logical source line.
Backslash followed by a newline causes the two lines to be folded into one before the pre-processor tries to deal with the line.

I made a little test macro for myself to try and use the same principles. Does the same job just for a bit more effort:

Code:

#ifndef getFunctionName
#define getFunctionName(x)                                                  \
{                                                                           \
    if (x == E_FAIL)                                                        \
    {                                                                       \
        const int newSize = strlen(#x) + 1;                                 \
        WCHAR* functionName = new WCHAR[newSize];                           \
        MultiByteToWideChar(CP_UTF8, 0, #x, -1, functionName, newSize);     \
        MessageBoxW(NULL, functionName, L"Function Name", 0);               \
        delete functionName;                                                \
    }                                                                       \
}
#endif

Thanks