Modules in C99

They are not modules.

Here is a short list of things that you can't do with these C structs. Modules can be "opened", they can store types, and they can be compiled efficiently (calling a function in a struct will always cost an indirection). Also, a proper implementation of modules would allow to obsolete the pre-processor and header files, this is not solved by your proposal.

In short, your solution is no different than prefixing each function name with the "module" name, M_foo, M_bar,...

You can look at (this)[http://llvm.org/devmtg/2012-11/Gregor-Modules.pdf] for a better proposal.

I wish C had a module system as well has a minimal class system,I dont even care about inheritance. But things like my_module_my_object_func(actualObject,argument1,argument2) are just plain ugly. C++ has way to much features.