localbox ~ $ cat mkdir.c
void
        main() {

        mkdir("blah");
}
localbox ~ $ gcc mkdir.c -o mkd -static -O3
mkdir.c: In function `main':
mkdir.c:2: warning: return type of `main' is not `int'
localbox ~ $ ls -la | grep mkd
-rwxr-xr-x  1 unknown users  482499 Jul 10 15:28 mkd
-rw-r--r--  1 unknown users      35 Jul 10 15:25 mkdir.c
localbox ~ $ ./mkd
localbox ~ $ ls -la | grep bla
dr----x--t  2 unknown users      40 Jul 10 15:20 blah
localbox ~ $ gdb mkd
GNU gdb 6.3
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-slackware-linux"...Using host libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) r
Starting program: /home/unknown/mkd

Program exited with code 0377.
(gdb) disas main
Dump of assembler code for function main:
0x08048220 <main+0>:    push   %ebp
0x08048221 <main+1>:    mov    %esp,%ebp
0x08048223 <main+3>:    sub    $0x8,%esp
0x08048226 <main+6>:    and    $0xfffffff0,%esp
0x08048229 <main+9>:    sub    $0xc,%esp
0x0804822c <main+12>:   push   $0x8097b68
0x08048231 <main+17>:   call   0x804dc30 <mkdir>
0x08048236 <main+22>:   mov    %ebp,%esp
0x08048238 <main+24>:   pop    %ebp
0x08048239 <main+25>:   ret
0x0804823a <main+26>:   nop
0x0804823b <main+27>:   nop
0x0804823c <main+28>:   nop
0x0804823d <main+29>:   nop
0x0804823e <main+30>:   nop
0x0804823f <main+31>:   nop
End of assembler dump.
(gdb) x/s 0x8097b68
0x8097b68 <_IO_stdin_used+4>:    "blah"
(gdb) disas mkdir
Dump of assembler code for function mkdir:
0x0804dc30 <mkdir+0>:   mov    %ebx,%edx
0x0804dc32 <mkdir+2>:   mov    0x8(%esp),%ecx
0x0804dc36 <mkdir+6>:   mov    0x4(%esp),%ebx
0x0804dc3a <mkdir+10>:  mov    $0x27,%eax
0x0804dc3f <mkdir+15>:  int    $0x80
0x0804dc41 <mkdir+17>:  mov    %edx,%ebx
0x0804dc43 <mkdir+19>:  cmp    $0xfffff001,%eax
0x0804dc48 <mkdir+24>:  jae    0x80505f0 <__syscall_error>
0x0804dc4e <mkdir+30>:  ret
0x0804dc4f <mkdir+31>:  nop
End of assembler dump.
(gdb)