From: Pedro Alves <palves@redhat.com>
To: Yue Lu <hacklu.newborn@gmail.com>
Cc: Pedro Alves <palves@redhat.com>,
gdb-patches <gdb-patches@sourceware.org>,
Thomas Schwinge <thomas@codesourcery.com>,
Luis Machado <lgustavo@codesourcery.com>,
bug-hurd@gnu.org
Subject: Re: [PATCH 1/2] Port gdbserver to GNU/Hurd
Date: Wed, 18 Sep 2013 12:30:00 -0000 [thread overview]
Message-ID: <52399CC6.1020807@redhat.com> (raw)
In-Reply-To: <CAB8fV=hcYutwy7KzeJyELziBaKZio0G9ZFX=FucRWav-T2_cnA@mail.gmail.com>
On 09/12/2013 04:05 AM, Yue Lu wrote:
> Honestly to say, I have copied them from function gnu_xfer_memory. But
> I think, before reference a pointer, check whether it was a NULL seems
> not a bad way :-).
We don't go around checking for NULL before _every_ pointer
dereference. :-)
NULL pointer checks are used when the function's semantics
give special meaning to NULL, like for example, for optional
parameters. If that's not the function's semantics, and you still
may see a NULL pointer, then that tells there's actually a bug
that triggered already elsewhere before the function in question
was called. IOW, a NULL check in these cases is just masking out a
bug in some caller. In some cases, we might add a gdb_assert to
catch the bug in a nicer way instead of just crashing.
I suspect that what may happen is that at some point it
was possible for GDB to select a no-longer-existing-thread
(though I can't see how in the current code), and then setting
breakpoints, or other operations that require reading memory
would crash.
--
Pedro Alves
next prev parent reply other threads:[~2013-09-18 12:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAB8fV=jJ64i91VW52ZmdnEDZhd1ZGTAykDqoFyPJanCP=5beqA@mail.gmail.com>
2013-09-03 8:03 ` [PATCH 2/2] " Yue Lu
2013-09-03 9:38 ` [PATCH 1/2] " Thomas Schwinge
2013-09-03 11:11 ` Pedro Alves
2013-09-03 13:09 ` Thomas Schwinge
2013-09-04 1:47 ` Yue Lu
2013-09-04 1:38 ` Yue Lu
2013-09-05 10:54 ` Yue Lu
2013-09-05 19:29 ` Pedro Alves
2013-09-05 19:39 ` Joel Brobecker
2013-09-05 21:38 ` Thomas Schwinge
2013-09-08 13:35 ` Yue Lu
2013-09-09 9:58 ` Thomas Schwinge
2013-09-18 12:12 ` Pedro Alves
2013-09-18 13:48 ` Yue Lu
2013-09-18 14:52 ` [Hurd/gnu-nat.c] Use ptid_t.lwpid to store, thread ids instead of ptid_t.tid. (was: Re: [PATCH 1/2] Port gdbserver to GNU/Hurd) Pedro Alves
2013-09-18 14:57 ` [PATCH 1/2] Port gdbserver to GNU/Hurd Pedro Alves
2013-09-22 12:58 ` Yue Lu
2013-09-06 18:53 ` Pedro Alves
2013-09-12 3:05 ` Yue Lu
2013-09-18 12:30 ` Pedro Alves [this message]
2013-09-18 12:37 ` Pedro Alves
2013-09-19 7:41 ` Yue Lu
2013-09-19 8:30 ` FAIL: gdb.base/nextoverexit.exp: next over exit (the program exited) (was: [PATCH 1/2] Port gdbserver to GNU/Hurd) Thomas Schwinge
2013-09-19 8:44 ` FAIL: gdb.base/nextoverexit.exp: next over exit (the program exited) Pedro Alves
2013-09-09 10:21 ` [PATCH 1/2] Port gdbserver to GNU/Hurd Yue Lu
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