[Bug c/51712] New: -Wtype-limits should not trigger for types of implementation-defined signedness

["jrnieder at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51712

             Bug #: 51712
           Summary: -Wtype-limits should not trigger for types of
                    implementation-defined signedness
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jrnieder@gmail.com
                CC: manu@gcc.gnu.org


Hi,

$ gcc -c -std=gnu99 -Wtype-limits -x c - <<-\EOF
enum test_enum {
    FOO,
    BAR
};

int valid(enum test_enum arg)
{
    return arg >= FOO && arg <= BAR;
}
EOF
<stdin>: In function âvalidâ:
<stdin>:8:9: warning: comparison of unsigned expression >= 0 is always true
[-Wtype-limits]
$ 

Since C99 (WG14/N1256 p105, lang.decl.typespec.enum.4) only says:

    Each enumerated type shall be compatible with char, a signed
    integer type, or an unsigned integer type. The choice of type
    is implementation-defined) but shall be capable of
    representing the values of all the members of the enumeration.

the (arg >= FOO) test is not actually redundant. It would be nice to
automatically suppress the warning in this case.

What do you think? Feasible?

Originally reported as http://bugs.debian.org/615525