How to write a Windows application without using WinMain

ccrtmainwinapiwinmain

Windows GUI applications written in C/C++ have 'WinMain' as an entry point (rather than 'main'). My understanding of this is that the compiler generates a 'main' function to be called by the C Runtime. This 'main' function sets up the necessary environment for the GUI and calls into 'WinMain' (specifying the instance handles etc.).

In short, I believe console and GUI application startup to differ in the following way:

Console application:
C Runtime –> 'main' function (hand-coded)

GUI application:
C Runtime –> 'main' function (compiler-generated) –> 'WinMain' function (hand-coded)

I would like to both validate this understanding and find out how I can hand-code a Windows GUI with just a 'main' function (i.e. without having to write 'WinMain').

Best Answer

You have an incorrect understanding. The difference between main and WinMain, apart from some differet initialization code, is the parameters passed to it.

main looks like this:

int main(int argc, char* argv[]);

While WinMain looks like this:

int WINAPI WinMain(HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow
);

Something has to setup those parameters and make the call, and that's the startup code. When you compile and link a program, one of the linker parameters is the entry point, and that will be, depending on a console or GUI app, a different bit of startup code.

You can certainly write your own startup code, just go into your visual c++ source directory and you can find the startup code, it's called crt0.c and it's in the VC\crt\src directory.

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