https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111525
Bug ID: 111525
Summary: Inconsistent Wsign-compare in c++ with ubsan
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zhroma at gcc dot gnu.org
Target Milestone: ---
$ cat test.cc
extern long global;
int foo (unsigned x) {
return x == ((global ? 64 : 32) - 1) / 8;
}
$ gcc -x c -c -Werror=sign-compare test.cc
$ gcc -x c -c -Werror=sign-compare test.cc -fsanitize=undefined
$ gcc -x c++ -c -Werror=sign-compare test.cc
$ gcc -x c++ -c -Werror=sign-compare test.cc -fsanitize=undefined
test.cc: In function ‘int foo(unsigned int)’:
test.cc:4:12: error: comparison of integer expressions of different signedness:
‘unsigned int’ and ‘int’ [-Werror=sign-compare]
4 | return x == ((global ? 64 : 32) - 1) / 8;
| ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: some warnings being treated as errors
Warning appears only for C++ with ubsan enabled. It seems that both sanitizer
and warning are implemented in front-end part, and C++ somehow issues warning
after instrumentation.
This actually breaks ubsan-bootstrap with -Werror enabled, from what I know all
versions since gcc-8 are affected.
configure --enable-languages=c,c++ --disable-multilib
--with-build-config=bootstrap-ubsan --enable-werror=yes && make
BOOT_CFLAGS="-Wno-error=array-bounds -Wno-error=format-overflow"
-Wno-error=array-bounds and -Wno-error=format-overflow are necessary as these
warnings have known issues under ubsan.
