https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94142
Bug ID: 94142
Summary: typeof enum member appears to give wrong signedness
Product: gcc
Version: 9.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: matthew.fernandez at gmail dot com
Target Milestone: ---
Consider the following code:
typedef enum { A, B } t;
t x;
__typeof__(A) y;
int foo() {
if (x == y)
return 0;
return 1;
}
With GCC 9.2.0, compiling with -Wsign-compare has the following to say:
$ gcc-9.2.0 -std=gnu11 -c -Wsign-compare goo.c
foo.c: In function 'foo':
foo.c:6:9: warning: comparison of integer expressions of different
sightedness: 't' {aka 'enum <anonymous>'} and 'int' [-Wsign-compare]
6 | if (x == y)
| ^~
This seems surprising to me. Shouldn't x and y have the same signedness as
they're both the type of the enum? It seems like somehow the type of an enum
member differs from the type of the enum itself. Either way, the warning seems
spurious here. Maybe #66773 is relevant.
Some cursory testing suggests to me this behaviour extends back to at least the
GCC 4 series. I could not find a version of Clang that has this behaviour.
