https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93626
Bug ID: 93626 Summary: [GCOV] incorrect coverage when compiled with option '-fsanitize=undefined' for typedef struct Product: gcc Version: 9.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: gcov-profile Assignee: unassigned at gcc dot gnu.org Reporter: yangyibiao at hust dot edu.cn CC: marxin at gcc dot gnu.org Target Milestone: --- $ gcov -v gcov (GCC) 9.2.0 Copyright (C) 2019 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-shared --enable-threads=posix --with-system-zlib --with-isl --enable-__cxa_atexit --disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch --disable-libssp --enable-gnu-unique-object --enable-linker-build-id --enable-lto --enable-plugin --enable-install-libiberty --with-linker-hash-style=gnu --enable-gnu-indirect-function --enable-multilib --disable-werror --enable-checking=release --enable-default-pie --enable-default-ssp --enable-cet=auto gdc_include_dir=/usr/include/dlang/gdc Thread model: posix gcc version 9.2.0 (GCC) $ cat small.c void main() { int t = 2; typedef struct { char v[t]; } B; B b; for (int i = 0; i < 2; i++) b.v[i] = 0; } $ gcc --coverage -O0 -fsanitize=undefined small.c; ./a.out; gcov small.c; cat small.c.gcov File 'small.c' Lines executed:100.00% of 9 Creating 'small.c.gcov' -: 0:Source:small.c -: 0:Graph:small.gcno -: 0:Data:small.gcda -: 0:Runs:1 1: 1:void main() 1: 2:{ 1: 3: int t = 2; 1: 4: typedef struct -: 5: { 3: 6: char v[t]; -: 7: } B; 1: 8: B b; 3: 9: for (int i = 0; i < 2; i++) 2: 10: b.v[i] = 0; 1: 11:} Line #6 is wrongly marked as executed three times. When compiled without option '-fsanitize=undefined', the coverage report is correct.