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[75.166.102.22]) by smtp.gmail.com with ESMTPSA id d25sm105127qtw.59.2021.08.03.15.33.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Aug 2021 15:33:02 -0700 (PDT) Subject: Re: Failures building glibc with mainline GCC To: Joseph Myers References: <033b535d-8adc-bb82-dff5-4e6d1d357358@gmail.com> <60297d58-80ed-105b-b020-c86ae5e7867c@gmail.com> Message-ID: <2ae709a5-5edf-268b-a7d1-7b8bc7ab3655@gmail.com> Date: Tue, 3 Aug 2021 16:33:01 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Martin Sebor via Libc-alpha Reply-To: Martin Sebor Cc: GCC Mailing List , Martin Sebor , libc-alpha@sourceware.org Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On 8/3/21 11:21 AM, Joseph Myers wrote: > On Tue, 3 Aug 2021, Martin Sebor via Gcc wrote: > >> Yes, we know about that one. What I'm asking for is the translation >> units with the other warnings you showed with the latest GCC (including >> the threader patches) on the other targets (including i686 and power). >> I don't have an easy way to create them using my setup. > > I've attached (all gzipped) hurdselect.i (i686-gnu, -O2 -Wall -Werror > -Wno-parentheses): Thanks. > > hurdselect.c: In function '_hurd_select': > hurdselect.c:555:7: error: 'ss' may be used uninitialized in this function [-Werror=maybe-uninitialized] > hurdselect.c:70:25: note: 'ss' was declared here This is a false positive caused by the overly restrictive analysis limits hardwired into GCC (like PR 85872). I have a patch that relaxes the limits and that avoids the warning in this case but it's not yet ready. > > and t.61.i (powerpc-linux-gnu, -O2 -Wall -Werror): > > In file included from t.61.c:437: > In function 'from_t_61_single', > inlined from 'gconv' at ../iconv/skeleton.c:568:15: > ../iconv/loop.c:440:22: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=] > In file included from t.61.c:437: > ../iconv/loop.c: In function 'gconv': > ../iconv/loop.c:382:17: note: at offset 2 into destination object 'bytebuf' of size 2 This is the same warning as Jeff noted on s390-linux-gnu and that I explained in my reply: https://gcc.gnu.org/pipermail/gcc/2021-July/236943.html There's nothing the warning alone can do to avoid triggering in these cases (unrolling too many iterations of a loop). The unroller does have code to avoid doing this (infer_loop_bounds_from_undefined) but it's not good enough. Using -fno-aggressive-loop-optimizations prevents the warning. > and dl-tls.i (powerpc64-linux-gnu, -O2 -finline-limit=2000 -Wall -Werror; > the -finline-limit=2000 option is necessary for the error and comes from > sysdeps/powerpc/powerpc64/Makefile): > > In file included from ../sysdeps/powerpc/dl-tls.c:20: > In function '_dl_allocate_tls_init', > inlined from '_dl_allocate_tls' at ../elf/dl-tls.c:621:10: > ../elf/dl-tls.c:529:10: error: array subscript -1 is outside array bounds of 'void[9223372036854775807]' [-Werror=array-bounds] > ../elf/dl-tls.c:544:40: error: array subscript -1 is outside array bounds of 'void[9223372036854775807]' [-Werror=array-bounds] > These warnings are reproducible even with a native x86_64 compiler and the same option. It's most likely due to the same root cause as PR 101600 (the one in comment #0, not comment #2). I don't have a fix for it yet but it shouldn't be too hard. Martin