Argument Type (WCHAR*) is incompatible with parameter of type "const char*)

Question

This is part of some CSGO code and I don't know how to fix this problem; It's on line 8 of the snippet shown below:

uintptr_t GetModuleBaseAddress(const char* modName) {
    HANDLE hSnap = CreateToolhelp32Snapshot(TH32CS_SNAPMODULE | TH32CS_SNAPMODULE32, procId);
    if (hSnap != INVALID_HANDLE_VALUE) {
        MODULEENTRY32 modEntry;
        modEntry.dwSize = sizeof(modEntry);
        if (Module32First(hSnap, &modEntry)) {
            do {
                if (!strcmp(modEntry.szModule, modName)) {
                    CloseHandle(hSnap);
                    return (uintptr_t)modEntry.modBaseAddr;
                }
            } while (Module32Next(hSnap, &modEntry));
        }
    }
}

Error message:

Argument Type (WCHAR*) is incompatible with parameter of type "const char*)

Answer 1

As mentioned in the comments, your problem lies in the fact that your (new) project has the "Use Unicode Character Set" option set for builds but the (old) code base expects to be built using the "Use Multi-Byte Character Set" option. (The former uses the wchar_t* type for strings in Windows API calls and structures, whereas the latter uses the char* type; these are incompatible pointers.)

So, the 'quick fix' is to set your project's build options to use the "Multi-Byte" character set. In Visual Studio 2019, this option is the project's Properties -> Advanced -> Character Set when you right-click on the project in the Solution Explorer; earlier versions of Visual Studio have the option in the General property tab, IIRC.

If you are using some other IDE, then you'll need to 'manually' undefine the UNICODE macro (which signals to the compiler that the "Unicode Character Set" is in use); an #undef UNICODE line before any of your #include <...> lines for the system headers would work.

For much (most) of the Windows API, this issue can also be resolved by using explicit wchar_t or char versions of structures and functions; for example, the GetModuleFileName function, mentioned in the comments, resolves to either GetModuleFileNameW or GetModuleFileNameA, depending on which character set is chosen for the build, and structures used in those calls have W and A versions defined explicitly. Thus, one can 'override' the default call for the project's setting by explicitly using the A- or W-suffixed versions of those functions and structures.

However, in your particular case, unfortunately, the TlHelp32.h header file (and the functions it defines) are not so well defined: There are no explicit A-suffixed versions, so you can't simply suffix your MODULEENTRY32 and Module32First references with an A, as one would like. (For Unicode builds, the W-suffixed versions simply overwrite the 'original' function and structure names, so these are then lost to your code.)

Thus, without changing your code to use TCHAR types throughout (TCHAR resolves to either char or wchar_t, depending on the character set option), your only sensible option is the aforementioned quick fix: change the build settings.