Re: debugging a dynamically loaded library

["H . J . Lu" <hjl at lucon dot org>]

On Mon, Sep 03, 2001 at 03:58:50PM -0700, Kevin Buettner wrote:
> On Aug 29,  4:07pm, H . J . Lu wrote:
> 
> > > (gdb) b main.c:23
> > > Breakpoint 1 at 0x80487fc: file main.c, line 23.
> > > (gdb) r
> > > Starting program: /home/kev/ctests/dynlib/main 
> > > 
> > > Breakpoint 1, main (argc=1, argv=0xbffffa2c) at main.c:23
> > > 23        init = dlsym(handle, "dso_init");
> > > (gdb) b dso_init
> > > Breakpoint 2 at 0x400188a2: file dso.c, line 10.
> > 
> > For some reason, it doesn't work for me:
> > 
> > GNU gdb 2001-08-29-cvs (MI_OUT)
> > ....
> > (gdb) b main.c:23
> > Breakpoint 1 at 0x8048820: file main.c, line 23.
> > (gdb) r
> > Starting program: /home/hjl/bugs/gdb/dlopen/main 
> > 
> > Breakpoint 1, main (argc=1, argv=0xbffff804) at main.c:23
> > 23        init = dlsym(handle, "dso_init");
> > (gdb) b dso_init
> > Cannot access memory at address 0x123
> > (gdb) p dso_init
> > $1 = {<text variable, no debug info>} 0x40017800 <dso_init>
> > (gdb) info shared
> > >From        To          Syms Read   Shared Object Library
> > 0x400281d0  0x40028fc0  Yes         /lib/libdl.so.2
> > 0x40047400  0x40147080  Yes         /lib/i686/libc.so.6
> > 0x40001eb0  0x40012f20  Yes         /lib/ld-linux.so.2
> > 0x400176d0  0x400178b0  Yes         ./dso.so
> > 
> > I am using glibc 2.2.4 on x86. It seems that gdb doesn't add the base
> > address of ./dso.so.
> 
> H. J.,
> 
> Could you try 
> 
>     http://sources.redhat.com/ml/gdb-patches/2001-09/msg00003.html
> 
> and let me know if it fixes the above problem?
> 

I just came back from a trip. I will give it try tomorrow. I know there
was at least one gcc bug, which generated bogus debug code for glibc.
I am wondering if

1327   FUN    0      36     00000000 31372  __strtol_internal:F(0,3)

is a valid stab entry. It it is valid, why does it trigger the
SOFUN_ADDRESS_MAYBE_MISSING code in gdb. Is that possible a linker
or assembler bug?


H.J.