Re: Help getting backtrace in gdb

[Kaushal Modi <kaushal.modi@gmail.com>]

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On Tue, Jun 27, 2017 at 7:27 PM Noam Postavsky <
npostavs@users.sourceforge.net> wrote:

> On Tue, Jun 27, 2017 at 6:01 PM, Kaushal Modi <kaushal.modi@gmail.com>
> wrote:
> >
> > My assumption was that Fsignal would get called before the seg fault.
>
> I would not expect it to be called, if you're strictly following the
> recipe for Bug#27504.
>
> >>
> >> You can try evaluating (signal 'wrong-number-of-arguments '(x y)) to
> >> see if your Fsignal breakpoint is working.
> >
> >
> > Nope, it does not work..
>

Hello all,

This is a non-Emacs question .. I am having trouble getting gdb to work.
But I need gdb to work to help provide more debug info for an Emacs bug.

If I use the gdb that has shipped with my RHEL OS, gdb is unable to catch
any of the errors that happen in Emacs.. even evaluating (error "foo") does
not give control back to gdb.

gdb version:

GNU gdb (GDB) Red Hat Enterprise Linux (7.2-75.el6)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.

So I built the latest gdb from source (v8.0.1), and there I get this
another issue (see below):

GNU gdb (GDB) 8.0.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./emacs...done.
SIGINT is used by the debugger.
Are you sure you want to change it? (y or n) [answered Y; input not from
terminal]
DISPLAY = :1.0
TERM = screen-256color
Breakpoint 1 at 0x55e4e7: file emacs.c, line 364.
Temporary breakpoint 2 at 0x582a67: file sysdep.c, line 1031.
(gdb) break Fsignal
Breakpoint 3 at 0x606ee5: file eval.c, line 1514.
(gdb) r -Q
Starting program: /home/kmodi/downloads/git/emacs/src/emacs -Q
Could not trace the inferior process.
Error: ptrace: No such processDuring startup program exited with code 127.
(gdb) q

Can I get help getting gdb working?
-- 

Kaushal Modi

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