[Bug c/82283] Wrong warning with -Wmissing-field-initializers

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82283

--- Comment #14 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:4b7d9f8f51bd96d290aac230c71e501fcb6b21a6

commit r12-7772-g4b7d9f8f51bd96d290aac230c71e501fcb6b21a6
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Mar 22 14:37:02 2022 -0400

    c: -Wmissing-field-initializers and designated inits [PR82283, PR84685]

    This patch fixes two kinds of wrong -Wmissing-field-initializers
    warnings.  Our docs say that this warning "does not warn about designated
    initializers", but we give a warning for

    1) the array case:

      struct S {
        struct N {
          int a;
          int b;
        } c[1];
      } d = {
        .c[0].a = 1,
        .c[0].b = 1, // missing initializer for field 'b' of 'struct N'
      };

    we warn because push_init_level, when constructing an array, clears
    constructor_designated (which the warning relies on), and we forget
    that we were in a designated initializer context.  Fixed by the
    push_init_level hunk; and

    2) the compound literal case:

      struct T {
        int a;
        int *b;
        int c;
      };

      struct T t = { .b = (int[]){1} }; // missing initializer for field 'c' of
'struct T'

    where set_designator properly sets constructor_designated to 1, but the
    compound literal causes us to create a whole new initializer_stack in
    start_init, which clears constructor_designated.  Then, after we've parsed
    the compound literal, finish_init flushes the initializer_stack entry,
    but doesn't restore constructor_designated, so we forget we were in
    a designated initializer context, which causes the bogus warning.  (The
    designated flag is also tracked in constructor_stack, but in this case,
    we didn't perform push_init_level between set_designator and start_init
    so it wasn't saved anywhere.)

            PR c/82283
            PR c/84685

    gcc/c/ChangeLog:

            * c-typeck.cc (struct initializer_stack): Add 'designated' member.
            (start_init): Set it.
            (finish_init): Restore constructor_designated.
            (push_init_level): Set constructor_designated to the value of
            constructor_designated in the upper constructor_stack.

    gcc/testsuite/ChangeLog:

            * gcc.dg/Wmissing-field-initializers-1.c: New test.
            * gcc.dg/Wmissing-field-initializers-2.c: New test.
            * gcc.dg/Wmissing-field-initializers-3.c: New test.
            * gcc.dg/Wmissing-field-initializers-4.c: New test.
            * gcc.dg/Wmissing-field-initializers-5.c: New test.