gdb/2450: gdb core dump in user-defined stack print command

[skip at pobox dot com]

>Number:         2450
>Category:       gdb
>Synopsis:       gdb core dump in user-defined stack print command
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 02 13:18:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Skip Montanaro
>Release:        6.7
>Organization:
>Environment:
GNU gdb 6.7
...
This GDB was configured as "i386-pc-solaris2.10".

Python2.5 or later.  (If tried against Python 2.4 or
earlier, replace PyEval_EvalFrameEx with PyEval_EvalFrame
in the user-defined pystack command.)

>Description:
I have a set of gdb commands which help me navigate around the Python interpreter stack.  A version is distributed with Python in .../Misc/gdbinit.

In recent versions of gdb they've quit working, causing gdb
itself to drop a core file.  Today I spent a little time
trying to narrow down the problem.  I've boiled it down to
this fairly simple user-defined command:

define pystack
    select-frame 0
    set $last = 0
    while $sp != $last
        if $pc > PyEval_EvalFrameEx && $pc < PyEval_EvalCodeEx
	    frame
        end
        set $last = $sp
        up-silently 1
    end
    select-frame 0
end

I can define the command, but if I try to execute it
gdb gets an apparent assertion error and dumps core.
Here's the gdb backtrace:

#0  0xfede5f85 in _lwp_kill () from /lib/libc.so.1
#1  0xfede2dfe in thr_kill () from /lib/libc.so.1
#2  0xfed911cb in raise () from /lib/libc.so.1
#3  0xfed715e9 in abort () from /lib/libc.so.1
#4  0x0808d62b in internal_vproblem (problem=0x82f04e0,
    file=0x828b9cf "../../gdb/regcache.c", line=<value optimized out>,
    fmt=0x828b9b4 "%s: Assertion `%s' failed.",
    ap=0x8046a6c "G\036%\bX\237+\b2") at ../../gdb/utils.c:794
#5  0x0808af93 in internal_verror (file=0x828b9cf "../../gdb/regcache.c",
    line=164, fmt=0x828b9b4 "%s: Assertion `%s' failed.",
    ap=0x8046a6c "G\036%\bX\237+\b2") at ../../gdb/utils.c:809
#6  0x0808afc9 in internal_error (file=0x828b9cf "../../gdb/regcache.c",
    line=164, string=0x828b9b4 "%s: Assertion `%s' failed.")
    at ../../gdb/utils.c:818
#7  0x080e2067 in register_type (gdbarch=0x833e370, regnum=50)
    at ../../gdb/regcache.c:164
#8  0x080ecaaa in evaluate_subexp_standard (expect_type=0x0, exp=0x11461640,
    pos=0x80473c4, noside=EVAL_AVOID_SIDE_EFFECTS) at ../../gdb/eval.c:511
#9  0x080e9d16 in evaluate_subexp (expect_type=0x0, exp=0x0, pos=0x8046974,
    noside=EVAL_AVOID_SIDE_EFFECTS) at ../../gdb/eval.c:75
#10 0x080eb910 in evaluate_subexp_standard (expect_type=0x0, exp=0x11461640,
    pos=0x80473c4, noside=EVAL_AVOID_SIDE_EFFECTS) at ../../gdb/eval.c:1780
#11 0x080e9d16 in evaluate_subexp (expect_type=0x0, exp=0x0, pos=0x8046974,
    noside=EVAL_AVOID_SIDE_EFFECTS) at ../../gdb/eval.c:75
#12 0x080ebc70 in evaluate_subexp_standard (expect_type=0x0, exp=0x11461640,
    pos=0x8046974, noside=EVAL_NORMAL) at ../../gdb/eval.c:1706
#13 0x080e9d16 in evaluate_subexp (expect_type=0x0, exp=0x0, pos=0x8046974,
    noside=EVAL_NORMAL) at ../../gdb/eval.c:75
#14 0x080e9d41 in evaluate_expression (exp=0x11461640) at ../../gdb/eval.c:165
#15 0x080b8c1c in execute_control_command (cmd=0xa82f9e8)
    at ../../gdb/cli/cli-script.c:492
#16 0x080b8b67 in execute_control_command (cmd=0xa82f968)
    at ../../gdb/cli/cli-script.c:445
#17 0x080b8f78 in execute_user_command (c=0x1b276ed0, args=0x0)
    at ../../gdb/cli/cli-script.c:310
#18 0x08089ecc in execute_command (p=0x831272f "", from_tty=1)
    at ../../gdb/top.c:441
#19 0x081201c9 in command_handler (command=0x8312728 "pystack")
    at ../../gdb/event-top.c:518
#20 0x08120e2a in command_line_handler (rl=0x196a9568 "pystack")
    at ../../gdb/event-top.c:804
#21 0x081c95ee in rl_callback_read_char () at ../../readline/callback.c:205
#22 0x0812035b in rl_callback_read_char_wrapper (client_data=0x0)
    at ../../gdb/event-top.c:177
#23 0x0811fdb7 in handle_file_event (event_file_desc=0)
    at ../../gdb/event-loop.c:728
#24 0x0811f229 in process_event () at ../../gdb/event-loop.c:341
#25 0x0811fac0 in gdb_do_one_event (data=0x0) at ../../gdb/event-loop.c:378
#26 0x0811ccc3 in catch_errors (func=0x811f920 <gdb_do_one_event>,
    func_args=0x0, errstring=0x8289a91 "", mask=6)
    at ../../gdb/exceptions.c:513
#27 0x080c81a5 in tui_command_loop (data=0x0) at ../../gdb/tui/tui-interp.c:152
#28 0x0811d28f in current_interp_command_loop () at ../../gdb/interps.c:276
#29 0x0808460b in captured_command_loop (data=0x0) at ../../gdb/main.c:99
#30 0x0811ccc3 in catch_errors (func=0x8084600 <captured_command_loop>,
---Type <return> to continue, or q <return> to quit---
    func_args=0x0, errstring=0x82833f8 "", mask=6)
    at ../../gdb/exceptions.c:513
#31 0x08083ea6 in captured_main (data=0x80479a4) at ../../gdb/main.c:870
#32 0x0811ccc3 in catch_errors (func=0x8083740 <captured_main>,
    func_args=0x80479a4, errstring=0x82833f8 "", mask=6)
    at ../../gdb/exceptions.c:513
#33 0x08083711 in gdb_main (args=0x80479a4) at ../../gdb/main.c:879
#34 0x080836d5 in main (argc=-18993666, argv=0x1) at ../../gdb/gdb.c:33
>How-To-Repeat:
* Run Python from gdb.
* At the interpreter prompt execute
    import os
    os.abort()
* At the resulting gdb prompt define the pystack command
  above and execute it.

Executing the above user-defined command seems to reliably
crash gdb for me on Solaris 10.  I tried this same command
on my Mac (Leopard, gdb 6.3.50-20050815) and it worked
as expected.  Unfortunately, I don't have a newer version
of gdb on my Mac or any older versions of gdb on Solaris
to test whether it seems to be version-related or
platform-related.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: