dev-cpp-users

[Dev-C++] Needed Header Files

[<and...@su...>]

Dear Users,

In C codes, some functions don´t need the
respective #include header file command, like
printf, system(blah...), etc.

Other specific functions do (pow versus math.h)

Why this happens?

Regards
Andre

Re: [Dev-C++] Needed Header Files

[<or...@vp...>]

André Macário Barros wrote:
> In C codes, some functions don´t need the
> respective #include header file command, like
> printf, system(blah...), etc.

They DO need the headers. Use the -Wall flag to see what happens, if you 
don't use the header. It will tell you something like:

prog.c:11: warning: implicit declaration of function `printf'

That is, printf is implicitly declared by the call to it. Now you 
probably wonder: "OK, that's fine, but shouldn't there be some linker 
error?" The question is right, there should be. But as far as I know, 
gcc (more accurately: mingw, dunno about other OSes) automatically links 
with a few system libs. Like "g++" is actually "gcc ... -lstdc++", so 
g++ automatically links with -lstdc++. Like this, gcc (mingw) links with 
-lm for example, and some other libs.

But anyhow, you should ALWAYS include the respective header file for the 
function to make portable code. Use -Wall to see if you missed something.

--
Greetings,
   Balázs