Thread: construction of source code

Originally Posted by sababa.sababa

1. I've understood that the source files can either have the file extension .h or .c, but when should I use which extension?

By convention, .h would be used to name a header file, whereas .c would be used to name a source file.

Originally Posted by sababa.sababa

2. I've got an idea for a game engine and want to use some kind of metadata publishing (XML for example) for doing the levels, characters etc. My question is: how to make the engine understand XML?

Write the code You probably would want to use an existing parser library though, e.g., Expat.

Originally Posted by sababa.sababa

Now I've studied some source code, and it seems that there're only void functions in .c files (except the main function) and returning functions in .h files.

Well, you have that COMPLETELY WRONG.

Normatively, a .c file contains function definitions (that is the functions themselves). .h files contain function declarations (aka prototypes), defines, and typedefs.

example.h

Code:

int myXfunc(int x, char *ptr);

example.c

Code:

int myXfunc(int x, char *ptr) {
     int i, len = strlen(ptr);
     for(i=0;i<len;i++) ptr[i] = 'A' + x;
     return len;
}

Headers and see section 'declaring functions' in functions(II)

Originally Posted by sababa.sababa

...so a good rule of thumb would be to put the function definitions in the .c files and all other stuff in the .h files. But why should I declare the function before I define it? Isn't it enough with a definition?

You can get away without prototypes by defining all your functions before main() and placing them in the right order, but

1) sometimes that is not possible; if func_b() can call func_a() AND func_a() can call func_b(), you need prototypes so that both functions are already declared when they are referenced in one another's definitions. Otherwise you get a compiler error, the same as just defining a function after main().
2) it is less comprehensible

Of course, that doesn't mean you actually need an .h file, it just means you should declare all your prototypes before main() or anything else is defined. The "secret purpose" of .h files is actually so you can compile .c files seperately, eg. on a large project. That's how the standard headers work -- they just contain prototypes referring to the functions already contained in precompiled libraries, so you don't have to recompile the entire C library all the time.