No warning about duplicate values in enum

[Basile Starynkevitch <basile@starynkevitch.net>]

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.

For readability of some weird code, or in the case of C code generated by other tools.

By the way, gcc version 12.2.0 (Debian 12.2.0-14) don't emit any warnings neither when used on your example as gcc -Wall -Wextra -fanalyzer /tmp/andrea.c -o /tmp/andrea

If you really want to get warnings, consider writing your GCC plugin (perhaps starting with https://github.com/bstarynk/bismon/ ....) or using static analysis tools like https://frama-c.com/

Regards.

NB my pet open source project is the RefPerSys open source inference engine (work in progress) on http://refpersys.org/

-- 
Basile Starynkevitch <basile@starynkevitch.net>
92340 Bourg-la-Reine, France
http://starynkevitch.net/Basile/ and http://refpersys.org/