https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87951
Bug ID: 87951
Summary: GCC warns about reaching end of non-void function when
all switch is completely handled
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vlovich at gmail dot com
Target Milestone: ---
If a function has a single switch statement that handles all enum values &
returns a value GCC will warn about the function not returning a value whereas
clang does not. GCC requires an explicit __builtin_unreachable() annotation
after the switch. As of C++17 it seems to now be undefined behaviour rather
than unspecified behaviour for an enum to have a value that's not enumerated.
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1766
> cat test.c
enum Enum {
A,
B,
};
int CoverMyBases(enum Enum x) {
switch (x) {
case A:
return 1;
case B:
return 0;
}
}
int main(int argc, const char **argv) {
CoverMyBases(A);
CoverMyBases(B);
return 0;
}
> g++-8 -Wall --std=c++17 test.c
test.c: In function 'CoverMyBases':
test.c:16:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
> clang++ -std=c++17 -Wall test.c
NOTE: Clang never warns about this even prior to C++17 or in C either.
