the source code for C header

[nopri]

hello all,

I'm newbie in linux C programming. I just couldn't understand how this works :

When i include xxx.h for example, when i view the content of xxx.h, it just contains constants or function name without the body, but i can using the function list in xxx.h, so where is the body of the function ?
And what is the purpose of a C file that only contains int errno;

thanks for reading and helping me...

NOP

[Serene]

I am not sure ,I think maybe it is following.

There are directories :/include and /lib ,it seem that /include are head files which include the function prototype but the function bodies are in lib in the /lib.when you u compiling source file which include *.h ,compiler will extract the function from lib file.

[pinoy]

They are stored in a library. The standard c library at least is stored in libc in most (if not all) UNIX.

And what is the purpose of a C file that only contains int errno;

It defines the errno symbol. The header can only declare it as "extern int errno;" Well it can define it, but if it gets included by multiple C files, then you are going to have multiple definitions of errno and the linker will complain.

[nopri]

thanks,

but if i want to know the function body, how do i get it ?
And how the compiler know where to find the function body ? Or it just know how.


thanks...
NOP

[ 17 October 2001: Message edited by: nopri ]

[EscapeCharacter]

if you want to see the code for the functions just look at the source code for libc, gcc knows where to find the libs because of the linker program ld which has a file in /etc called ls.so.conf which contains the paths to the libs on your system, and yes gcc links using libc by default, if you want to do it manually which makes no difference add -lc to the commandline

[bwkaz]

And if you want to know where the source for libc can be gotten from, there are tarballs on the GNU Project's FTP site.

However, I don't know the full path now, because the GNU server is full. There's a mirror that contains glibc source here -- get the newest glibc tarball, along with the one for Linux threads (the same version) if you want to look at threading code. Once they are downloaded, go into wherever you downloaded it to, and do a tar xzf <filename>.tar.gz -- replace <filename> with whatever you downloaded (hint: use tab-completion for the filename).

This should create a directory that you can cd into and look at the source.

[ 17 October 2001: Message edited by: bwkaz ]