From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id C0B9C38515F3; Thu, 12 May 2022 09:41:41 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C0B9C38515F3 From: "j.gaffiot at laposte dot net" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/105580] New: False warning "potential null pointer dereference" raised when using istreambuf_iterator and any "-O" flag Date: Thu, 12 May 2022 09:41:41 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: j.gaffiot at laposte dot net X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 12 May 2022 09:41:41 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105580 Bug ID: 105580 Summary: False warning "potential null pointer dereference" raised when using istreambuf_iterator and any "-O" flag Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: j.gaffiot at laposte dot net Target Milestone: --- I found what I believe is a false positive with g++ 12 when using the "null-dereference" warning and istreambuf_iterator with any level of optimisation. And of course the "-Werror" flag is mandatory in my company process. I have searched for such similar bug report. This behavior does not show up with g++ 11.2.0 or g++ 9.4.0. Minimal example (basically the first lines of the cppreference example for istreambuf_iterator): #include #include int main() { std::istringstream in{"Hello, world"}; std::istreambuf_iterator it(in), end; std::string ss{it, end}; return 0; } Compiled with: g++-12 -O -Wnull-dereference Compiler version (default g++-12 on Ubuntu 22.04): g++ (Ubuntu 12-20220319-1ubuntu1) 12.0.1 20220319 (experimental) [master r12-7719-g8ca61ad148f] Full version: Using built-in specs. COLLECT_GCC=3Dg++-12 COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/x86_64-linux-gnu/12/lto-wrapper OFFLOAD_TARGET_NAMES=3Dnvptx-none:amdgcn-amdhsa OFFLOAD_TARGET_DEFAULT=3D1 Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion=3D'Ubuntu 12-20220319-1ubuntu1' --with-bugurl=3Dfile:///usr/share/doc/gcc-12/README.B= ugs --enable-languages=3Dc,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=3D/usr --with-gcc-major-version-only --program-suffix=3D-12 --program-prefix=3Dx86_64-linux-gnu- --enable-shared --enable-linker-build-= id --libexecdir=3D/usr/lib --without-included-gettext --enable-threads=3Dposix --libdir=3D/usr/lib --enable-nls --enable-clocale=3Dgnu --enable-libstdcxx-= debug --enable-libstdcxx-time=3Dyes --with-default-libstdcxx-abi=3Dnew --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=3Drelea= se --with-target-system-zlib=3Dauto --enable-objc-gc=3Dauto --enable-multiarch --disable-werror --enable-cet --with-arch-32=3Di686 --with-abi=3Dm64 --with-multilib-list=3Dm32,m64,mx32 --enable-multilib --with-tune=3Dgeneric --enable-offload-targets=3Dnvptx-none=3D/build/gcc-12-OcsLtf/gcc-12-12-2022= 0319/debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc-12-OcsLtf/gcc-12-12-20= 220319/debian/tmp-gcn/usr --enable-offload-defaulted --without-cuda-driver --enable-checking=3Drelease --build=3Dx86_64-linux-gnu --host=3Dx86_64-linux-gnu --target=3Dx86_64-linu= x-gnu Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 12.0.1 20220319 (experimental) [master r12-7719-g8ca61ad148f] (Ubuntu 12-20220319-1ubuntu1)=