Re: [PATCH] c++: -Wmissing-field-initializers and empty class [PR110064]

[Jason Merrill via Gcc-patches]

On 7/19/23 15:20, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.  We might also improve the diagnostic for base classes, perhaps by 
teaching dump_simple_decl about DECL_FIELD_IS_BASE?

-- >8 --

Let's suppress -Wmissing-field-initializers for empty classes.

Here I don't think I need the usual COMPLETE_TYPE_P/dependent_type_p
checks.

        PR c++/110064

gcc/cp/ChangeLog:

        * typeck2.cc (process_init_constructor_record): Don't emit
        -Wmissing-field-initializers for empty classes.

gcc/testsuite/ChangeLog:

        * g++.dg/warn/Wmissing-field-initializers-3.C: New test.
---
  gcc/cp/typeck2.cc                             |  3 +-
  .../warn/Wmissing-field-initializers-3.C      | 48 +++++++++++++++++++
  2 files changed, 50 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/warn/Wmissing-field-initializers-3.C

diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 1c204c8612b..582a73bb053 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -1874,7 +1874,8 @@ process_init_constructor_record (tree type, tree init, 
int nested, int flags,
             to zero.  */
          if ((complain & tf_warning)
              && !cp_unevaluated_operand
-             && !EMPTY_CONSTRUCTOR_P (init))
+             && !EMPTY_CONSTRUCTOR_P (init)
+             && !is_really_empty_class (fldtype, /*ignore_vptr*/false))
            warning (OPT_Wmissing_field_initializers,
                     "missing initializer for member %qD", field);
  
diff --git a/gcc/testsuite/g++.dg/warn/Wmissing-field-initializers-3.C b/gcc/testsuite/g++.dg/warn/Wmissing-field-initializers-3.C
new file mode 100644
index 00000000000..a8d75b92bd1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wmissing-field-initializers-3.C
@@ -0,0 +1,48 @@
+// PR c++/110064
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wmissing-field-initializers" }
+
+struct B { };
+struct D : B {
+    int x;
+    int y;
+};
+
+struct E {
+  int x;
+  int y;
+  B z;
+};
+
+template<typename> struct X { };
+
+template<typename T>
+struct F {
+  int i;
+  int j;
+  X<T> x;
+};
+
+int
+main ()
+{
+  D d = {.x=1, .y=2}; // { dg-bogus "missing" }
+  (void)d;
+  E e = {.x=1, .y=2}; // { dg-bogus "missing" }
+  (void)e;
+  F<int> f = {.i=1, .j=2 }; // { dg-bogus "missing" }
+  (void)f;
+}
+
+template<typename T>
+void fn ()
+{
+  F<T> f = {.i=1, .j=2 }; // { dg-bogus "missing" }
+  (void)f;
+}
+
+void
+g ()
+{
+  fn<int> ();
+}

base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832