From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17941 invoked by alias); 24 Jul 2014 02:39:31 -0000 Mailing-List: contact binutils-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: binutils-owner@sourceware.org Received: (qmail 17919 invoked by uid 89); 24 Jul 2014 02:39:30 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.4 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-Spam-User: qpsmtpd, 2 recipients X-HELO: mail-pa0-f46.google.com Received: from mail-pa0-f46.google.com (HELO mail-pa0-f46.google.com) (209.85.220.46) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Thu, 24 Jul 2014 02:39:28 +0000 Received: by mail-pa0-f46.google.com with SMTP id lj1so2927272pab.19 for ; Wed, 23 Jul 2014 19:39:27 -0700 (PDT) X-Received: by 10.66.168.204 with SMTP id zy12mr1601849pab.19.1406169567074; Wed, 23 Jul 2014 19:39:27 -0700 (PDT) Received: from [192.168.1.23] ([124.127.118.42]) by mx.google.com with ESMTPSA id tl3sm15063048pac.41.2014.07.23.19.39.24 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 23 Jul 2014 19:39:26 -0700 (PDT) Message-ID: <53D071D9.60503@gmail.com> Date: Thu, 24 Jul 2014 02:39:00 -0000 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Michael Eager , Michael Eager CC: binutils@sourceware.org, gdb-patches@sourceware.org Subject: Re: [PATCH] gdb/microblaze-tdep.c: Check whether less than zero in conditional expression References: <53CBCC2F.7040702@gmail.com> <53D01542.9020107@eagerm.com> <53D031E7.40602@gmail.com> <53D03483.2060203@eagercon.com> <53D0352D.1020205@gmail.com> <53D0682E.9090201@gmail.com> <53D06E5F.1070802@eagerm.com> In-Reply-To: <53D06E5F.1070802@eagerm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2014-07/txt/msg00185.txt.bz2 On 07/24/2014 10:24 AM, Michael Eager wrote: > On 07/23/14 18:58, Chen Gang wrote: >> >> >> On 07/24/2014 06:20 AM, Chen Gang wrote: >>> On 07/24/2014 06:17 AM, Michael Eager wrote: >>>> On 07/23/14 15:06, Chen Gang wrote: >>>>> On 07/24/2014 04:04 AM, Michael Eager wrote: >>>>>> On 07/20/14 07:03, Chen Gang wrote: >>>>>>> Use typecast 'size_t' on 'reg', not only avoid the related >>>>>>> warning, but >>>>>>> also check whether less than zero -- for 'reg' is type 'int', and >>>>>>> sizeof >>>>>>> (dwarf2_to_reg_map) is less than 0x7fff. >>>>>>> >>>>>>> It is quoted in gdb_assert(), so need check 'reg' whether less >>>>>>> than zero. >>>>>>> And the related warning (with '-W'): >>>>>>> >>>>>>> ../../binutils-gdb/gdb/microblaze-tdep.c:667:3: error: >>>>>>> comparison between signed and unsigned integer expressions >>>>>>> [-Werror=sign-compare] >>>>>>> >>>>>>> ChangeLog: >>>>>>> >>>>>>> * microblaze-tdep.c (microblaze_dwarf2_reg_to_regnum): Check >>>>>>> whether >>>>>>> less tha zero in conditional expression. >>>>>>> >>>>>>> >>>>>>> Signed-off-by: Chen Gang >>>>>>> --- >>>>>>> gdb/microblaze-tdep.c | 2 +- >>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git a/gdb/microblaze-tdep.c b/gdb/microblaze-tdep.c >>>>>>> index 7e89241..9bec260 100644 >>>>>>> --- a/gdb/microblaze-tdep.c >>>>>>> +++ b/gdb/microblaze-tdep.c >>>>>>> @@ -664,7 +664,7 @@ static int dwarf2_to_reg_map[78] = >>>>>>> static int >>>>>>> microblaze_dwarf2_reg_to_regnum (struct gdbarch *gdbarch, int >>>>>>> reg) >>>>>>> { >>>>>>> - gdb_assert (reg < sizeof (dwarf2_to_reg_map)); >>>>>>> + gdb_assert ((size_t) reg < sizeof (dwarf2_to_reg_map)); >>>>>>> return dwarf2_to_reg_map[reg]; >>>>>>> } >>>>>> >>>>>> I don't see anything in the patch which does what you describe, >>>>>> checking whether reg is less than zero. Converting a signed >>>>>> integer to an unsigned integer is not a way to check whether >>>>>> it is less than zero. This is better: >>>>>> >>>>>> + gdb_assert (reg >= 0 && (size_t) reg < sizeof (dwarf2_to_reg_map)); >>>>>> >>>>> >>>>> Yeah, it is common statement. It is also OK to me, although after type >>>>> cast, 'reg >=0' can be omited (it can let code simpler, but let code >>>>> not quit easy understanding). >>>> >>>> No, if you want to verify that the value is greater than zero, >>>> this cannot be omitted. A negative value would converted to >>>> a positive value by the cast. There no reason to believe that >>>> this would cause the other half of the test to fail. >>>> >>> >>> When an 'int' negative value converted to a positive value, it will be >>> larger than 0x7fff which must be larget than 'sizeof >>> (dwarf2_to_reg_map)'. >>> >> >> If what I said is correct, your idea/suggestions is still OK to me: easy >> understanding has higher priority than keeping source code simple. > > Yes, you are correct. Took me a moment to think through. > OK, thank you for your work. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed