$ objdump -d main > main.txt
     

Here is the portion of main.txt for the function sumFirst. After linking we see that function sumFirst begins at address 0x080483c8. Otherwise the output is the same as when we used objdump on sumFirst.o.

...
080483c8 <sumFirst>:
 80483c8:       55                      push   %ebp
 80483c9:       89 e5                   mov    %esp,%ebp
 80483cb:       83 ec 10                sub    $0x10,%esp
 80483ce:       c7 45 f8 00 00 00 00    movl   $0x0,0xfffffff8(%ebp)
 80483d5:       c7 45 fc 01 00 00 00    movl   $0x1,0xfffffffc(%ebp)
 80483dc:       eb 0a                   jmp    80483e8 <sumFirst+0x20>
 80483de:       8b 45 fc                mov    0xfffffffc(%ebp),%eax
 80483e1:       01 45 f8                add    %eax,0xfffffff8(%ebp)
 80483e4:       83 45 fc 01             addl   $0x1,0xfffffffc(%ebp)
 80483e8:       8b 45 fc                mov    0xfffffffc(%ebp),%eax
 80483eb:       3b 45 08                cmp    0x8(%ebp),%eax
 80483ee:       7e ee                   jle    80483de <sumFirst+0x16>
 80483f0:       8b 45 f8                mov    0xfffffff8(%ebp),%eax
 80483f3:       c9                      leave
 80483f4:       c3                      ret
 80483f5:       90                      nop
...