minimal shared libaraies

Ikebo · 07-01-2005, 04:21 PM

Can anyone explain why ldd reports dependencies on certain shared libraries even though I make the attempt to link them into the binary?

The binary is noticeably bigger, ~500k as opposed to ~7k, but it seems there is no difference in the shared library dependencies.

Code:

[ike:~/temp]$ cat main.c
int main(void)
{
   return 0;
}
[ike:~/temp]$ gcc -o main main.c
[ike:~/temp]$ ls -l
total 12
-rwxr-xr-x  1 ike users 7348 Jul  1 17:12 main
-rw-r--r--  1 ike users   33 Jul  1 17:12 main.c
[ike:~/temp]$ ldd main
        linux-gate.so.1 =>  (0xffffe000)
        libc.so.6 => /lib/libc.so.6 (0x4101d000)
        /lib/ld-linux.so.2 (0x41004000)
[ike:~/temp]$ gcc -o main main.c `locate libc.a` `locate libc.so.6` `locate ld-linux.so.2`
[ike:~/temp]$ ls -l
total 513
-rwxr-xr-x  1 ike users 518706 Jul  1 17:12 main
-rw-r--r--  1 ike users     33 Jul  1 17:12 main.c
[ike:~/temp]$ ldd main
        linux-gate.so.1 =>  (0xffffe000)
        libc.so.6 => /lib/libc.so.6 (0x4101d000)
        /lib/ld-linux.so.2 (0x41004000)

rstewart · 07-01-2005, 04:45 PM

Uh,

But aren't you linking in the non-shared object version of libc in the larger executable? You seem to be resolving the libc dependencies with the .a, not the .so version of the library in your second compilation.

sind · 07-01-2005, 10:43 PM

This should do what you're after:

$ gcc -static -o main main.c

EDIT: Actually, that's probably not what you were after... Linking statically against libc without specifying -static might need a bit more work as there is an implicit -lc on the linker's command line - see:

$ gcc -v -o main main.c

EDIT: I ran nm on the compiled executable, after running:

$ gcc -o main main.c /usr/lib/libc.a

And there is one reference to the shared glibc:

w pthread_setcancelstate@@GLIBC_2.0

Don't know if I've helped at all or just babbled...

~sind

Ikebo · 07-01-2005, 11:17 PM

I don't think the question was clear from the start, but you have answered it. Thanks for the reply.