On 3/13/23 14:29, Marek Polacek wrote:
On Sat, Mar 11, 2023 at 04:48:14PM +0000, Jonathan Wakely via Gcc wrote:
On Sat, 11 Mar 2023, 12:53 Basile Starynkevitch, <bas...@starynkevitch.net>
wrote:
Hello all,
Andrea observed that:
In gcc 8.3.0, compiling
enum
test
{
FIRST = 1,
SECOND = 1,
THIRD = 2
};
int
main (void)
{
return 0;
}
generates no warning even with -Wextra.
I believe that the C standard (which I don't have here, but see also
https://port70.net/~nsz/c/c11/n1570.html or buy it from ISO) explicitly
allow duplicate values in enum.
Of course it does, it's perfectly valid. Nobody has said it should be
rejected. The request is for a warning, because for *some* uses of enums
duplicates are not wanted.
And as I said in the other thread about the very same issue, it's
<https://gcc.gnu.org/PR16186> which is assigned to me and I hope to
implement it for GCC 14.
Marek
Then consider perhaps:
prototyping that warning in your own GCC plugin (and test it on a bunch
of existing open source software).
adding some explicit new warning option to enable that new warning or
adding another option to disable that warning in a compilation unit.
adding some explicit #pragma to disable that new warning (with the hope
that tools generating C++ code would later -in 2024- emit the pragma
appropriately)
Since there are some valid, probably weird, cases (notably generated C++
code, or low level driver code where two different enum names need to
share some common values, ....) where having duplicate values in enum
may make sense.
Regards
--
Basile Starynkevitch <bas...@starynkevitch.net>
(only mine opinions / les opinions sont miennes uniquement)
92340 Bourg-la-Reine, France
web page: starynkevitch.net/Basile/ & refpersys.org
