[Bug c/39589] make -Wmissing-field-initializers=2 work with "designated initializers" ?

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39589

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #2 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Szikra István from comment #1)
> I have the same (or similar) problem, and would like to have an option to
> enable warnings for incomplete structure initialization with designated
> initializers, where not all fields were explicitly assigned. 

I don't think GCC devs would be against this in principle if someone provided a
sensible patch: http://gcc.gnu.org/contribute.html

The relevant code is at gcc/c/c-typeck.c: pop_init_level

  /* Warn when some struct elements are implicitly initialized to zero.  */
  if (warn_missing_field_initializers
      && constructor_type
      && TREE_CODE (constructor_type) == RECORD_TYPE
      && constructor_unfilled_fields)
    {
        bool constructor_zeroinit =
         (vec_safe_length (constructor_elements) == 1
          && integer_zerop ((*constructor_elements)[0].value));

        /* Do not warn for flexible array members or zero-length arrays.  */
        while (constructor_unfilled_fields
               && (!DECL_SIZE (constructor_unfilled_fields)
                   || integer_zerop (DECL_SIZE (constructor_unfilled_fields))))
          constructor_unfilled_fields = DECL_CHAIN
(constructor_unfilled_fields);

        if (constructor_unfilled_fields
            /* Do not warn if this level of the initializer uses member
               designators; it is likely to be deliberate.  */
            && !constructor_designated
            /* Do not warn about initializing with ` = {0}'.  */
            && !constructor_zeroinit)
          {
            if (warning_at (input_location, OPT_Wmissing_field_initializers,
                            "missing initializer for field %qD of %qT",
                            constructor_unfilled_fields,
                            constructor_type))
              inform (DECL_SOURCE_LOCATION (constructor_unfilled_fields),
                      "%qD declared here", constructor_unfilled_fields);
          }
    }


Perhaps sinking the !constructor_designated check into the if, and adding an
'else'? Or simply deleting the check and doing:

            if (warning_at (input_location, 
                            !constructor_designated check ?
OPT_Wmissing_field_initializers : OPT_Wmissing_field_initializers_2,

where OPT_Wmissing_field_initializers_2 corresponds to a new option
Wmissing-field-initializers=2 that needs to be added to c.opt (and documented
in doc/invoke.texi).