GDB mainline segfaults on 32bit threaded program.

[Manoj Iyer <manjo at austin dot ibm dot com>]

GDB (mainline cvs) built 32bit on ppc64 machine running sles9 dumps core
on a multithreaded program. gdb segfaults only when I set a breakpoint on
the thread fucntion and decide to stop there.

1. cc -o tbug_dwarf2 tbug.c -g dwarf-2 -lpthread
2. gdb tbug_dwarf2
3. br main
4. br tf
5. run <---- segfalts here
6. c


Attached is a testcase that can re-create this problem "tbug.c"

I used GDB to debug this core produced, here is the backtrace...
#0  0x0fe05694 in strcmp () from /lib/tls/libc.so.6
#1  0x100cfba8 in lookup_symtab (name=0xffffc360 "/root/manjo/tbug.c")
    at symtab.c:185
#2  0x100d9254 in symtab_from_filename (argptr=0xffffc480, p=0x104caafa
":tf",
    is_quote_enclosed=0, not_found_ptr=0x0) at linespec.c:1523
#3  0x100d99c4 in decode_line_1 (argptr=0xffffc480, funfirstline=1,
    default_symtab=0x0, default_line=0, canonical=0x0, not_found_ptr=0x0)
    at linespec.c:744
#4  0x100a432c in breakpoint_re_set_one (bint=0x104ca958) at
breakpoint.c:7157
#5  0x10051748 in do_catch_errors (uiout=0x104ca958, data=0x0) at
top.c:524
#6  0x10053d20 in catcher (func=0x1005172c <do_catch_errors>,
    func_uiout=0x104712c8, func_args=0xffffc848, func_val=0xffffc850,
    func_caught=0xffffc854,
    errstring=0x7f7f7f7f <Address 0x7f7f7f7f out of bounds>,
gdberrmsg=0x0,
    mask=6) at top.c:431
#7  0x10053d80 in catch_errors (func=0xffffc2f0, func_args=0x104cbeb8,
    errstring=0x7f7f7f7f <Address 0x7f7f7f7f out of bounds>, mask=0)
    at top.c:536
#8  0x100a2b14 in breakpoint_re_set () at breakpoint.c:7340
#9  0x100d2bd4 in new_symfile_objfile (objfile=0x104ca958, mainline=0,
verbo=0)
    at symfile.c:741
#10 0x100d4634 in symbol_file_add_with_addrs_or_offsets (abfd=0x104d0220,
    from_tty=0, addrs=0x0, offsets=0x0, num_offsets=0, mainline=0,
flags=8)


The macro FILENAME_CMP in symtab.c:185 uses the strcmp to do the
comparison, symtab_to_fullname() function returns NULL for s->fullname and
this causes strcmp to segfault. Although syntab.c:185 checks if full_path
!= NULL but it does not check if  const char *fp = symtab_to_fullname (s);
is not equal to NULL. I dont know what causes symtab_to_fullname() to
return NULL.

Thanks
Manoj Iyer