[Bug c/94428] New: Reintroduce -Wzero-length-array

[kees at outflux dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94428

            Bug ID: 94428
           Summary: Reintroduce -Wzero-length-array
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kees at outflux dot net
  Target Milestone: ---

It would be nice to gain "-Wzero-length-array" so we can enforce this standard
in the Linux kernel once all conversions have moved struct to flexible array
members. Clang supports this as a distinct warning, but gcc currently only
warns about this under "-pedantic -std=c99", which is not a workable
combination for Linux. ;)

$ clang -Wzero-length-array -o bounds-clang bounds.c
bounds.c:20:15: warning: zero size arrays are an extension
[-Wzero-length-array]
    char data[0];
              ^

$ gcc -Wzero-length-array -o bounds-gcc bounds.c
gcc: error: unrecognized command line option ‘-Wzero-length-array’


$ gcc -pedantic -std=c99  -o bounds-gcc bounds.c
bounds.c:20:10: warning: ISO C forbids zero-size array ‘data’ [-Wpedantic]
   20 |     char data[0];
      |          ^~~~