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Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.

From: Alexander Cherepanov <ch3root at openwall dot com>
To: Florian Weimer <fweimer at redhat dot com>, Andreas Schwab <schwab at linux-m68k dot org>
Cc: Mark Wielaard <mjw at redhat dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, Josh Stone <jistone at redhat dot com>
Date: Wed, 22 Apr 2015 11:58:51 +0300
Subject: Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.
Authentication-results: sourceware.org; auth=none
References: <1427193579-26102-1-git-send-email-mjw at redhat dot com> <55117118 dot 1080706 at arm dot com> <20150324211541 dot GA2318 at blokker dot redhat dot com> <1429608058 dot 1938 dot 53 dot camel at bordewijk dot wildebeest dot org> <5537587D dot 5020707 at redhat dot com> <87vbgo6040 dot fsf at igel dot home> <55375CBE dot 9000908 at redhat dot com>

On 2015-04-22 11:33, Florian Weimer wrote:

On 04/22/2015 10:25 AM, Andreas Schwab wrote:

Florian Weimer <fweimer@redhat.com> writes:

I think the safer change is to use -0x80000000 as the value of the
constant, without making it unsigned.


-0x80000000 has unsigned type.


Ugh.  The joys of C.

Using a cast would rely on a GCC extension, so one has to write
(-2147483647 - 1) to get the desired value.  Wow.

Given that stdint.h is already included it's perhaps easier to just useINT32_MIN?

I've replied about it and other issues in the previous thread but I'mafraid I'm lost all Cc there. Here it is:


https://sourceware.org/ml/libc-alpha/2015-04/msg00257.html

--
Alexander Cherepanov

References:
- Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.
  - From: Mark Wielaard
- Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.
  - From: Florian Weimer
- Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.
  - From: Andreas Schwab
- Re: [PATCH] elf.h SHF_EXCLUDE signed int 31 bit shift triggers undefined behaviour.
  - From: Florian Weimer

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