Re: About header files

Christoph Scholtes said:

Hi,

I have some questions about header files:

Say I have a file functions.c which contains a couple of functions. I
have declared some structs in this file too. The structs are defined in
main.c. Now I create a header file which represents the interface of
functions.c to my main program file main.c.
I put in the header file: all function prototypes with keyword extern
and the declarations of the structs, which are defined in the main
program.

Do I include the header file functions.h in my file functions.c to get
the struct declarations or do I explicitely declare the structs in
functions.c and not include the header file?

Unless you are doing opaque types:

struct type definition goes in header
struct definitions go in the functions that need them

If you are doing opaque types:
struct type definition goes in module's .c file
struct type declaration goes in module's header
pointers to struct types are defined in the functions that need them



About standard libraries: functions.c uses stdio.h, stdlib.h and
string.h.

Those are headers, not libraries.

Thus, I include the header files. main.c also uses stdlib.c
and stdio.h. Do I include them again or do I use inclusion guards to
check if they are already included (e.g. in functions.c)?

Include them as often as you like. They are already protected by inclusion
guards.

If a variable is declared static, is it still legal to pass it on as a
function argument to a function outside of the file?

Yes.

The keyword extern in front of a function prototype in my header file
says that the function is defined somewhere else, right?

I certainly hope so, since you wouldn't want to define the function in the
header file!!

Do I HAVE to
declare the function prototype as extern in the header file?

No. For functions, it's the default, and it can be omitted. Indeed, it
almost always /is/ omitted.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)
.

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