https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109050
Bug ID: 109050
Summary: UBsan failed to detect out-of-bound at -O0/1/2/s
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: shaohua.li at inf dot ethz.ch
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
For the following code, UBsan failed to detect the out-of-bound access at all
opt levels. Clang can detect it at all opt levels.
Compiler explorer: https://godbolt.org/z/TK35hvPrK
% cat a.c
long a;
int b;
int main() {
int c[4]={0, 1, 2, 3};
a = 0;
for (; a <= 2; a++)
c[a - 9806816] |= b;
}
%
% gcc-tk -O0 -fsanitize=undefined a.c && ./a.out
%
% gcc-tk -O1 -fsanitize=undefined a.c && ./a.out
%
% clang -O1 -fsanitize=undefined a.c && ./a.out
/a.c:7:5: runtime error: index -9806816 out of bounds for type 'int[4]'
...
% gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-7e9dd9de169034810b92d47bf78284db731fa5da/libexec/gcc/x86_64-pc-linux-gnu/13.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-7e9dd9de169034810b92d47bf78284db731fa5da
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.1 20230221 (experimental) (GCC)
%
