How can I detect if I'm compiling for a 64bits architecture in C++

Question

In a C++ function I need the compiler to choose a different block if it is compiling for a 64 bit architecture.

I know a way to do it for MSVC++ and g++, so I\'ll po

Answer 1

If your using Windows, your probably better to get the "PROCESSOR_ARCHITECTURE" environment variable from the registry because sizeof(PVOID) will equal 4 if its a 32bit process running on a 64bit operating system (aka WOW64):

    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, _T("SYSTEM\CurrentControlSet\\Control\\Session Manager\\Environment"), 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
        LPSTR szArch = new CHAR[100];

        ZeroMemory(szArch, 100);

        if (RegQueryValueEx(hKey, _T("PROCESSOR_ARCHITECTURE"), NULL, NULL, (LPBYTE)szArch, &dwSize) == ERROR_SUCCESS) {
            if (strcmp(szArch, "AMD64") == 0)
                this->nArchitecture = 64;
            else
                this->nArchitecture = 32;
        } else {
            this->nArchitecture = (sizeof(PVOID) == 4 ? 32 : 64);
        }

        RegCloseKey(hKey);
    }