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Re: Backtraces broken on i386 by unorthodox encoding of push %ebp
- From: Joel Brobecker <brobecker at adacore dot com>
- To: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- Cc: Richard Smith <richard at ex-parrot dot com>, gdb at sourceware dot org
- Date: Sat, 30 Mar 2013 13:07:43 -0700
- Subject: Re: Backtraces broken on i386 by unorthodox encoding of push %ebp
- References: <alpine dot LRH dot 2 dot 02 dot 1303301849040 dot 2445 at sphinx dot mythic-beasts dot com> <20130330195008 dot GA11994 at host2 dot jankratochvil dot net>
> > However, when I have this form of prologue, gdb doesn't recongnise
> > it, and doesn't give a meaningful backtrace.
>
> You should always provide unwind information and then it is irrelevant which
> instructions and/or which their coding you use.
Agreed, and that could be the instant fix.
But if he cannot get the unwind information with the binary, it might
indeed be easy enough to improve the prologue analyzer for x86. On
x86_64, on the other hand, we made the conscious design decision to rely
more on unwind info, so it's a little more questionable whether we'd
want to do that for this target.
The thing I wanted to add to Richard is that there is a very high
chance that the only way to get this fixed in GDB is by submitting
a patch himself (to gdb-patches).
--
Joel