From: Joel Brobecker <brobecker@adacore.com>
To: Simon Marchi <simon.marchi@polymtl.ca>
Cc: Tim Newsome <tim@sifive.com>, gdb <gdb@sourceware.org>
Subject: Re: gdb requires watchpoints to fire after the write
Date: Wed, 29 Aug 2018 15:47:00 -0000 [thread overview]
Message-ID: <20180829154739.GB2521@adacore.com> (raw)
In-Reply-To: <3833782b96d47551263798eb78f448bd@polymtl.ca>
> I don't have experience with many different architectures, but as far as I
> know, the expectation of the GDB is that the watchpoint is reported after
> the write. Otherwise it wouldn't need to save the value of the watched
> expression. That's also how software watchpoints seem to work.
>
> The easiest way to deal with this would be to match GDB's expectation. But
> if you really prefer the behavior of reporting the watchpoint before the
> event, I suppose it's always possible to teach GDB about this, but it's a
> less trivial task. Especially that when you GDB evaluates whether the watch
> expression has changed value, it would need to consider the not-yet-written
> value in memory.
>
> I'm also curious to know if other architectures work in this way (report the
> event before the write actually take place).
I seem to remember some architectures having different behaviors,
and so we have a couple of entry points in GDB. For architecture-specific
settings, we have gdbarch_have_nonsteppable_watchpoint. For target-specific
settings, you would use target_have_steppable_watchpoint. (IIRC)
--
Joel
next prev parent reply other threads:[~2018-08-29 15:47 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-28 22:08 Tim Newsome
2018-08-29 15:33 ` Simon Marchi
2018-08-29 15:47 ` Joel Brobecker [this message]
2018-08-29 15:56 ` Pedro Alves
2018-08-29 16:02 ` Simon Marchi
2018-08-29 17:29 ` Pedro Alves
2018-08-29 20:13 ` Tim Newsome
2018-08-29 20:58 ` Tom Tromey
2018-08-30 8:05 ` Joel Brobecker
2018-08-31 15:37 ` Pedro Alves
2018-08-31 15:13 ` Pedro Alves
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