https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115405
Bug ID: 115405 Summary: wrong code with _BitInt() sign-extension with -fno-strict-aliasing -O1 and above Product: gcc Version: 15.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: zsojka at seznam dot cz CC: jakub at gcc dot gnu.org Target Milestone: --- Host: x86_64-pc-linux-gnu Target: x86_64-pc-linux-gnu Created attachment 58389 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58389&action=edit reduced testcase Output: $ x86_64-pc-linux-gnu-gcc -O0 testcase.c $ ./a.out $ x86_64-pc-linux-gnu-gcc -O1 testcase.c $ ./a.out Aborted I think the code should have defined behavior at least at -O1 or with -fno-strict-aliasing. $ x86_64-pc-linux-gnu-gcc -v Using built-in specs. COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r15-1122-20240609121028-g8bb6b2f4ae1-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/15.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++ --enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra --disable-bootstrap --with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld --with-as=/usr/bin/x86_64-pc-linux-gnu-as --enable-libsanitizer --disable-libstdcxx-pch --prefix=/repo/gcc-trunk//binary-trunk-r15-1122-20240609121028-g8bb6b2f4ae1-checking-yes-rtl-df-extra-nobootstrap-amd64 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 15.0.0 20240609 (experimental) (GCC)