In a C/C++ program how does the system (windows, linux, mac OS X) call the main() function

Question

I am looking for a more technical explanation then the OS calls the function. Can anyone help me out or point me to a website or book?

Answer 1

The .exe file (or equivalent on other platforms) contains an 'entry point' address. To a first approximation, the OS loads the relevant sections of the .EXE file into ram, and then jumps to the entry point.

As others have said, this entry point will not be 'main', but will instead be a part of the runtime library - it will do things like initialising static objects, setting up the argc/argv parameters, setting up stdin/stdout/stderr, etc. When it's done all that, it will call your main() function. When main exits, the runtime goes through an analagous process of passing your return code back to the environment, calling static destructors, calling _atexit routines, etc.

If you have MS tools (perhaps not the freebie ones), then you have all the runtime source, and an easy way to look at it is to put a breakpoint on the closing brace of your main() method, and single step back up into the runtime.