https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96496
Bug ID: 96496
Summary: Conversion to enum with underlying type bool produces
wrong result
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fw at gcc dot gnu.org
Target Milestone: ---
enum E : bool { One, Two };
int
f1 (int x)
{
return (E) x;
}
The conversion must first be to type bool, according to:
“If the enumeration type has a fixed underlying type, the value is first
converted to that type by integral conversion, if necessary, and then to the
enumeration type.”
<http://eel.is/c++draft/expr.static.cast#10>
And that must produce a comparison against zero:
“A zero value, null pointer value, or null member pointer value is converted to
false; any other value is converted to true.”
<http://eel.is/c++draft/conv.bool#1>
Currently, GCC performs a bit mask (at -O2):
_Z2f1i:
movl %edi, %eax
andl $1, %eax
ret
