https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71386
Bug ID: 71386 Summary: Wrong code on c++14 (GCC trunk) Product: gcc Version: 7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: anton.mitrokhin at phystech dot edu Target Milestone: --- Created attachment 38625 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38625&action=edit Reproducer It looks like gcc emits wrong code with 14th standard features (or I may be wrong). The reproducer concatenates two lists, but the last three elements always end up to be zero on -O3, and on -O0 the last two elements a getting trashed. Compiling with latest clang works fine. Reproducer: 1. -O0: > g++ -std=c++14 -O0 crash.cpp -o out > ./out > 3 2 1 0 -1490624600 32600 2. -O3: > g++ -std=c++14 -O3 crash.cpp -o out > ./out > 3 2 1 0 0 0 3. clang: > clang++ -fsanitize=undefined -fsanitize=memory -Wall -O3 crash.cpp -std=c++14 > -o out > ./out > 1 2 3 1 2 3 > gcc -v: Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/export/users/amitrokh/gcc_trunk/bin/../libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /export/users/gnutester/stability/svn/trunk/configure --with-arch=corei7 --with-cpu=corei7 --enable-clocale=gnu --with-system-zlib --enable-shared --with-demangler-in-ld --enable-cloog-backend=isl --with-fpmath=sse --with-pkgversion=Revision=237011/svn-rev:237016/ --prefix=/export/users/gnutester/stability/work/trunk/64/install --enable-languages=c,c++,fortran,java,lto Thread model: posix gcc version 7.0.0 20160601 (experimental) (Revision=237011/svn-rev:237016/)