[Bug breakpoints/13791] New: crash in breakpoint.c

["lvd at golang dot org" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13791

             Bug #: 13791
           Summary: crash in breakpoint.c
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
        AssignedTo: unassigned@sourceware.org
        ReportedBy: lvd@golang.org
    Classification: Unclassified


title has most likely cause.  originally reported as a bug in the Go compiler:
http://code.google.com/p/go/issues/detail?id=2818

but closer inspection (gdb gdb) reveals

(this stack trace from 7.3.1 built from ports on FreeBSD 9.0 release)


Program received signal SIGBUS, Bus error.
[Switching to Thread 802c07400 (LWP 100131)]
0x0000000000500a65 in bpstat_what (bs_head=0x8030652c0) at breakpoint.c:4579
4579          switch (b->type)
#0  0x0000000000500a65 in bpstat_what (bs_head=0x8030652c0)
    at breakpoint.c:4579
#1  0x0000000000564f95 in handle_inferior_event (ecs=0x7fffffffd400)
    at infrun.c:4144
#2  0x0000000000561dd3 in wait_for_inferior (treat_exec_as_sigtrap=0)
    at infrun.c:2610
#3  0x00000000005610b3 in proceed (addr=34366555520, siggnal=TARGET_SIGNAL_0, 
    step=0) at infrun.c:2136
#4  0x000000000055a360 in run_command_1 (args=0x0, from_tty=1, 
    tbreak_at_main=0) at infcmd.c:600
#5  0x000000000055a3a0 in run_command (args=0x0, from_tty=1) at infcmd.c:610
#6  0x00000000004b54d4 in do_cfunc (c=0x802dbeb00, args=0x0, from_tty=1)
    at ./cli/cli-decode.c:67
#7  0x00000000004b8495 in cmd_func (cmd=0x802dbeb00, args=0x0, from_tty=1)
    at ./cli/cli-decode.c:1777
#8  0x00000000004542ac in execute_command (p=0x802c1e083 "", from_tty=1)
    at top.c:428
#9  0x000000000057d3de in command_handler (command=0x802c1e080 "")
    at event-top.c:499
#10 0x000000000057d9c2 in command_line_handler (rl=0x802d1e67c "run")
    at event-top.c:704
#11 0x0000000800d6b087 in rl_callback_read_char () from /lib/libreadline.so.8
#12 0x000000000057ca51 in rl_callback_read_char_wrapper (client_data=0x0)
    at event-top.c:177
#13 0x000000000057d2a9 in stdin_event_handler (error=0, client_data=0x0)
    at event-top.c:434
#14 0x000000000057b9fb in handle_file_event (data=...) at event-loop.c:831
#15 0x000000000057b072 in process_event () at event-loop.c:402
#16 0x000000000057b15b in gdb_do_one_event (data=0x0) at event-loop.c:467
#17 0x000000000057594f in catch_errors (func=0x57b090 <gdb_do_one_event>, 
    func_args=0x0, errstring=0x781003 "", mask=6) at exceptions.c:521
#18 0x00000000004ccdf4 in tui_command_loop (data=0x0) at ./tui/tui-interp.c:172
#19 0x00000000005760c7 in current_interp_command_loop () at interps.c:291
#20 0x0000000000449791 in captured_command_loop (data=0x0) at ./main.c:228
#21 0x000000000057594f in catch_errors (func=0x449780 <captured_command_loop>, 
    func_args=0x0, errstring=0x762a2f "", mask=6) at exceptions.c:521
#22 0x000000000044a6c7 in captured_main (data=0x7fffffffdb50) at ./main.c:936
#23 0x000000000057594f in catch_errors (func=0x4497d0 <captured_main>, 
    func_args=0x7fffffffdb50, errstring=0x762a2f "", mask=6)
    at exceptions.c:521
#24 0x000000000044a751 in gdb_main (args=0x7fffffffdb50) at ./main.c:945
#25 0x00000000004494be in main (argc=2, argv=0x7fffffffdbc8) at gdb.c:44


closer inspection of b and it's origin in bs on line 4579 reveals bs actually
points to a string instead of a struct with real pointers.  No matter what
dwarf the Go compiler generates, that should probably not happen.

Compiling gdb without thread support makes the issue go away.

Setting a breakpoint at main.main in the Go program, before running, seems to
work around the problem, therefor i conclude it's likely due to an
uninitialized bs_head variable.

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