From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 452193858004; Sat, 19 Dec 2020 18:20:36 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 452193858004 From: "ngmr80 at web dot de" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/98394] New: Concept with auto... template parameter pack in if-statement causes compilation error Date: Sat, 19 Dec 2020 18:20:36 +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: 10.1.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: ngmr80 at web dot de 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 attachments.created 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: Sat, 19 Dec 2020 18:20:36 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98394 Bug ID: 98394 Summary: Concept with auto... template parameter pack in if-statement causes compilation error Product: gcc Version: 10.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: ngmr80 at web dot de Target Milestone: --- Created attachment 49807 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D49807&action=3Dedit Preprocessed source In C++20, when using a concept 'C' with an auto... template parameter pack = in an if-statement, the compiler reports the error "'C' does not constrain a type.". The same concept, however, _is_ usable in other contexts. Example: template concept C =3D true; int main() { auto b =3D C<1, 2>; // ok if (C<1, 2>); // error } -- Output of g++-10 -v -save-temps -std=3Dc++20 main.cpp Using built-in specs. COLLECT_GCC=3Dg++-10 COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper OFFLOAD_TARGET_NAMES=3Dnvptx-none:amdgcn-amdhsa:hsa OFFLOAD_TARGET_DEFAULT=3D1 Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion=3D'Ubuntu 10.1.0-2ubuntu1~18.04' --with-bugurl=3Dfile:///usr/share/doc/gcc-10/README.= Bugs --enable-languages=3Dc,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix= =3D/usr --with-gcc-major-version-only --program-suffix=3D-10 --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 --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-10-eDoCEC/gcc-10-10.1.0/= debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc-10-eDoCEC/gcc-10-10.1.0/deb= ian/tmp-gcn/usr,hsa --without-cuda-driver --enable-checking=3Drelease --build=3Dx86_64-linux-gnu --host=3Dx86_64-linux-gnu --target=3Dx86_64-linux-gnu Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 10.1.0 (Ubuntu 10.1.0-2ubuntu1~18.04)=20 COLLECT_GCC_OPTIONS=3D'-v' '-save-temps' '-std=3Dc++2a' '-shared-libgcc' '-mtune=3Dgeneric' '-march=3Dx86-64' /usr/lib/gcc/x86_64-linux-gnu/10/cc1plus -E -quiet -v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE main.cpp -mtune=3Dgeneric -march=3Dx86-64 -s= td=3Dc++2a -fpch-preprocess -fasynchronous-unwind-tables -fstack-protector-strong -Wfo= rmat -Wformat-security -o main.ii ignoring duplicate directory "/usr/include/x86_64-linux-gnu/c++/10" ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/10/include-fi= xed" ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/include/c++/10 /usr/include/x86_64-linux-gnu/c++/10 /usr/include/c++/10/backward /usr/lib/gcc/x86_64-linux-gnu/10/include /usr/local/include /usr/include/x86_64-linux-gnu /usr/include End of search list. COLLECT_GCC_OPTIONS=3D'-v' '-save-temps' '-std=3Dc++2a' '-shared-libgcc' '-mtune=3Dgeneric' '-march=3Dx86-64' /usr/lib/gcc/x86_64-linux-gnu/10/cc1plus -fpreprocessed main.ii -quiet -dumpbase main.cpp -mtune=3Dgeneric -march=3Dx86-64 -auxbase main -std=3Dc+= +2a -version -fasynchronous-unwind-tables -fstack-protector-strong -Wformat -Wformat-security -o main.s GNU C++17 (Ubuntu 10.1.0-2ubuntu1~18.04) version 10.1.0 (x86_64-linux-gnu) compiled by GNU C version 10.1.0, GMP version 6.1.2, MPFR version 4.0.1, MPC version 1.1.0, isl version isl-0.19-GMP GGC heuristics: --param ggc-min-expand=3D100 --param ggc-min-heapsize=3D131= 072 GNU C++17 (Ubuntu 10.1.0-2ubuntu1~18.04) version 10.1.0 (x86_64-linux-gnu) compiled by GNU C version 10.1.0, GMP version 6.1.2, MPFR version 4.0.1, MPC version 1.1.0, isl version isl-0.19-GMP GGC heuristics: --param ggc-min-expand=3D100 --param ggc-min-heapsize=3D131= 072 Compiler executable checksum: 435c9a72f92ce04eba08a47828fa63c4 main.cpp: In function =E2=80=98int main()=E2=80=99: main.cpp:7:9: error: =E2=80=98C=E2=80=99 does not constrain a type 7 | if (C<1, 2>); // error | ^~~~~~~ main.cpp:2:9: note: concept defined here 2 | concept C =3D true; | ^=