https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98467
Bug ID: 98467
Summary: gcc optimizes tapping code away
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: bernd.edlinger at hotmail dot de
Target Milestone: ---
Consider this test case:
$ cat test.cc
struct MyClass;
struct ptr {
MyClass* get() { return t; }
MyClass* t;
};
struct MyClass { void call(); };
void MyClass::call() {
*(char*)(nullptr) = 1;
}
static void intermediate(ptr p) {
p.get()->call();
}
int main() {
intermediate(ptr{new MyClass});
}
$ g++ -g -O0 test.cc
$ ./a.out
Segmentation fault (core dumped)
$ g++ -g -Og test.cc
$ ./a.out
$ g++ -g -O1 test.cc
$ ./a.out
$ g++ -g -O2 test.cc
$ ./a.out
Segmentation fault (core dumped)
$ g++ -g -O3 test.cc
$ ./a.out
Segmentation fault (core dumped)
$ g++ -g -Ofast test.cc
$ ./a.out
Segmentation fault (core dumped)
It is somehow unexpected that this code is optimized
away only at -Og -O1, but not at very high or very low optimization levels.
I would even say although the code is of course invalid, it should
not be optimized away, as it might be a debug-code that intentionally taps.
