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Re: [PATCH] Remove bogosities from dwarf2cfi.c:cfi_pop_frame()
- From: Andrew Cagney <ac131313 at ges dot redhat dot com>
- To: Richard dot Earnshaw at arm dot com
- Cc: Mark Kettenis <kettenis at chello dot nl>,gdb-patches at sources dot redhat dot com
- Date: Wed, 10 Jul 2002 12:17:54 -0400
- Subject: Re: [PATCH] Remove bogosities from dwarf2cfi.c:cfi_pop_frame()
- References: <200207100924.KAA09464@cam-mail2.cambridge.arm.com>
Mark
>
> Index: ChangeLog
> from Mark Kettenis <kettenis@gnu.org>
>
> * dwarf2cfi.c (cfi_pop_frame): Use alloca() for regbuf.
> Don't call get_current_frame().
>
Heads up,
I think the write_register_bytes() call should be replaced by
regcache_register_write(current_regcache, ). This is new code so it
doesn't need to go through any of that nasty write_register_bytes() stuff.
Andrew
Why is this code trying to poke directly into the regcache at all? AFAICT
it should be operating on the pseudo registers not the cache.
[cooked]
Hmm, yes, good point. It should at least use regcache_cpy() so that it
is ``bug compatible'' with generic_pop_dummy_frame()(1).
At present GDB saves/restores registers in a confused sort of way.
Firstly, the save/restore operation (see regcache_cpy):
- for old targets it iterates over 0..NUM_REGS (the full raw register
space) using write_register_bytes() to restore the registers.
- for new targets it iterates over 0..NUM_REGS (the full raw register
space) using regcache_write() to directly transfer the raw registers.
It then uses this single mechanism(2) to handle two orthogonal
situtations, and that is the problem:
- saving / restoring a raw register cache before / after an inferior
function call. Here, a select list of raw registers should be transfered.
- unwinding a stack frame, storing those unwound register values, and
hence having the effect of poping one or more frames. Here, a select
list of cooked registers should be stored.
Andrew
(1) I also suspect that some cleanups would let the function in question
be eliminated from dwarf2cfi but that is another story.
(2) I believe the regcache changes were ``bug compatible''.