From: Paul Koning <paulkoning@comcast.net>
To: Pedro Alves <palves@redhat.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH][gdb] fix unsigned overflow in charset.c
Date: Tue, 09 Oct 2018 17:40:00 -0000 [thread overview]
Message-ID: <FBF59187-8B90-4A9C-B44C-C98F27A676AA@comcast.net> (raw)
In-Reply-To: <1acace4a-a5c6-abaf-f070-9c2e6768b6f2@redhat.com>
> On Oct 9, 2018, at 1:31 PM, Pedro Alves <palves@redhat.com> wrote:
>
> On 10/09/2018 06:19 PM, Paul Koning wrote:
>> This fixed an overflow in pointer arithmetic that crashes GDB on Mac OS.
>
> _unsigned_ overflow? That isn't undefined. Do we really want to trap
> those? I don't think GCC's version does that.
>
> From:
> https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#silencing-unsigned-integer-overflow
> seems like there's a way to disable it.
>
> Thanks,
> Pedro Alves
You're right, it was an LLVM build. I know unsigned overflow is well defined with integers; is that true for pointers?
Given that GDB triggers this issue, should the GDB build do that LLVM workaround if LLVM is used to build it?
But it seems simpler to use the proposed patch; clearly the intent is to back up a pointer by -(space_left) and doing that operation on a signed type seems like a logical thing to do, it makes the intended meaning clear.
paul
next prev parent reply other threads:[~2018-10-09 17:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-09 17:19 Paul Koning
2018-10-09 17:31 ` Pedro Alves
2018-10-09 17:40 ` Paul Koning [this message]
2018-10-09 17:57 ` John Baldwin
2018-10-09 18:10 ` Paul Koning
2018-10-09 19:58 ` John Baldwin
2018-10-10 8:51 ` Pedro Alves
2018-10-11 20:16 ` John Baldwin
2018-10-16 15:58 ` Pedro Alves
2018-10-17 18:38 ` John Baldwin
2018-10-17 18:47 ` Paul Koning
2018-10-17 21:51 ` Pedro Alves
2018-10-17 23:28 ` Paul Koning
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