Missing line numbers from debug symbols for library in whole program, but not on its own
I'm seeing an odd issue when trying to use gdb to debug a test program for a package built with libtool. If I run libtool --mode=execute gdb .libs/libfoo.so and ask it to list the source of some function list Bar::Baz, I get the source code as expected. If I run libtool --mode=execute gdb binary, I can break in Bar::Baz(), and see its arguments in a stack trace, but I get no source file or line numbers, like so:
#7 0x018348e5 in Bar::Baz(Qux*, Quux*) () from /path/to/libfoo.so
^^^^^^^^^^^ <--- debug symbols are present!
Similarly, if I try to list Bar::Baz when debugging the executable, I get
No line number known for 'Bar::Baz'.
I have confirmed that the binary is linked with -g, and I can list its main function, so I know some of the debug information is present are present.
When I say info sources, I get a full listing of the files from which the library is built, with correct absolute paths. When I say info shared, I get the correct path listed to the object file, with a Yes in the Syms column.
Any further ideas what could be going wrong, and how to fix it?
Edit 1: By accident, I ran objdump -g on the offending library, and got the following output:
/path/to/foo.so.0.0.0: file format elf32-i386
objdump: /path/to/foo.so.0.0.0: no recognized debugging information
This is surprising, since objdump -h (what I had tried to run) lists a bunch of .debug_* sections. The objdump manual suggests readelf -w as well, and that seems to print a huge pile of information. I need to go look through at what it actually provides, though.
Edit 2: So, readelf -w has produced some enlightenment. For whatever reason, the shared object file doesn't seem to contain the debugging information from the vast majority any of the objects linked into it. Based on the Makefiles, it's possible that the command that actually gathers up the objects into the shared library isn't passed -g, and so that information isn't properly propagated. The funny thing is that this works (has full debug information) on all our other configurations, including the same compiler version on x86_64 (versus the present x86).
Edit 3: Actually went through a full rebuild with the modified Makefile with -g added on the LDFLAGS, and it made no difference. Now I'm well and truly baffled.
Answer
This is an answer to an old question, but your problem matched mine, but none of the solutions worked. Here is what worked for me.
Change CFLAGS -g to "-g -gstabs".
objdump was not recognizing the dwarf style debug information. -gstabs changes this format to one that works with objdump -g and objdump -S and my debugger.
Hope it helps.
NOTE: For me, I was building a linux kernel. This change was make in the linux kernel's Makefile.