https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111399
Bug ID: 111399
Summary: Sanitizer code generation smarter than warnings
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: david at westcontrol dot com
Target Milestone: ---
Given this code :
int sign(int x) {
if (x < 0) return -1;
if (x == 0) return 0;
if (x > 0) return 1;
}
and compiled with "-O2 -Wall", gcc is unable to see that all possible cases for
"x" are covered, so it generates a "control reaches end of non-void function
[-Wreturn-type]" warning. It would be nice if gcc could see this is a false
positive, but analysis and warnings can't be perfect.
However, if I add the flag "-fsanitize=undefined", the compiler is smart enough
to see that all cases are covered, and there is no call to
__ubsan_handle_missing_return generated.
If the sanitizer code generation can see that all cases are covered, why can't
the -Wreturn-type warning detection? I'm guessing it comes down to the
ordering of compiler passes and therefore the level of program analysis
information available at that point. But perhaps the -Wreturn-type pass could
be done later when the information is available?
