[Question] stripped lib and it's line numbers

[Taeung Song]

Hi,

I have a question.
I believe objdump can't show line numbers for a stripped program.
But 'objdump -l' can do that in some cases ?

For example,
libc-2.23.so I use is stripped but objdump -l show it's filename:line 
numbers.

   $ file /lib/x86_64-linux-gnu/libc-2.23.so
/lib/x86_64-linux-gnu/libc-2.23.so: ELF 64-bit LSB shared object, 
x86-64, version 1 (GNU/Linux), dynamically linked, interpreter 
/lib64/ld-linux-x86-64.so.2, 
BuildID[sha1]=369de0e1d833caa693af17f17c83ba937f0a4dad, for GNU/Linux 
2.6.32, stripped

   $ objdump -dlS /lib/x86_64-linux-gnu/libc-2.23.so 
--start-address=0x7bf50 --stop-address=0x7c240

/lib/x86_64-linux-gnu/libc-2.23.so:     file format elf64-x86-64


Disassembly of section .text:

000000000007bf50 <_IO_adjust_column@@GLIBC_2.2.5+0x40>:
_IO_flush_all_lockp():
/build/glibc-GKVZIf/glibc-2.23/libio/genops.c:760
    7bf50:	41 57                	push   %r15
    7bf52:	41 56                	push   %r14
    7bf54:	41 89 fe             	mov    %edi,%r14d
    7bf57:	41 55                	push   %r13
    7bf59:	41 54                	push   %r12
    7bf5b:	55                   	push   %rbp
    7bf5c:	53                   	push   %rbx
    7bf5d:	48 83 ec 28          	sub    $0x28,%rsp
/build/glibc-GKVZIf/glibc-2.23/libio/genops.c:766
    7bf61:	85 ff                	test   %edi,%edi

...

No such file /build/glibc-GKVZIf/glibc-2.23/libio/genops.c.
But I found the above line numbers are correct at glibc-2.23 tag
of git://sourceware.org/git/glibc.git

How can objdump show line numbers for libc-2.23.so ?


Thanks,
Taeung