https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65425
Bug ID: 65425 Summary: code optimization leads to spurious FP exception Product: gcc Version: 4.9.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: p.vanhoof at oma dot be Created attachment 35035 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35035&action=edit program that triggers the bug Compile the attached test case with gcc -O3 -ftrapping-math -fno-math-errno bug.c -lm This produces no output. Running the executable will result in a spurious FP exception. This happens with all gcc versions I tested since 4.7.0. Versions 4.6.4 and earlier work correctly, so this is a regression. It looks like the code is being optimized with the implicit assumption that FP exceptions are not trapped. However, using the -ftrapping-math flag should prevent such optimizations (and should be the default as well). % gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/local/gcc492/libexec/gcc/x86_64-unknown-linux-gnu/4.9.2/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../gcc492/configure --prefix=/usr/local/gcc492 --enable-languages=c,c++,fortran Thread model: posix gcc version 4.9.2 (GCC)