https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597
Bug ID: 107597
Summary: LTO causes static inline variables to get a
non-uniqued global symbol
Product: gcc
Version: 8.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: cfsteefel at arista dot com
Target Milestone: ---
The following was seen with gcc 11.3.1 (centos7 based) and gcc 8.4 (also
centos7 based).
The following code produces a GNU extension unique symbol for NonTemplated::x
when flto is not used ('u' in nm), but a global non-unique symbol when flto is
used, even when building a shared library ('B' in nm).
class NonTemplated {
static inline int x;
public:
void doFoo() {
x++;
}
};
int main() {
NonTemplated n;
n.doFoo();
return 0;
}
> g++ -std=gnu++17 -O2 -shared -fPIC -o libFoo.so -flto test.cpp
> nm ./libFoo.so | c++filt | grep NonTemplated
000000000020102c B NonTemplated::x
> g++ -std=gnu++17 -O2 -shared -fPIC -o libFoo.so test.cpp
> nm ./libFoo.so | c++filt | grep NonTemplated
000000000020102c u NonTemplated::x
When compiled under clang++, the symbol is `V` (weak) regardless of flto is
used or not.
The resulting symptom of this is that Address Sanitizer will flag the variable
NonTemplated::X as an ODR violation, if the class is included into more than
one flto compiled shared library.
