[C PATCH] Don't warn on = { } initialization (PR c/63480)

[Marek Polacek]

PR63480 points out that -Wmissing-field-initializers warns about
initializing with { }.  Given that we suppress the warning for
initializing with { 0 }, I think it makes sense to suppress it
for { } as well.
(Initializing with { } is a GNU extension and -pedantic warns on that.)

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2014-10-08  Marek Polacek  <pola...@redhat.com>

        PR c/63480
        * c-typeck.c (pop_init_level): Don't warn about initializing
        with { }.

        * gcc.dg/pr63480.c: New test.

diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index b3b82bb..5c0697a 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -7436,7 +7436,11 @@ pop_init_level (location_t loc, int implicit,
        }
     }
 
-  if (vec_safe_length (constructor_elements) != 1)
+  /* Initialization with { } counts as zeroinit.  */
+  if (vec_safe_length (constructor_elements) == 0)
+    constructor_zeroinit = 1;
+  /* If the constructor has more than one element, it can't be { 0 }.  */
+  else if (vec_safe_length (constructor_elements) != 1)
     constructor_zeroinit = 0;
 
   /* Warn when some structs are initialized with direct aggregation.  */
@@ -7463,7 +7467,7 @@ pop_init_level (location_t loc, int implicit,
            /* 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}'.  */
+           /* Do not warn about initializing with { 0 } or with { }.  */
            && !constructor_zeroinit)
          {
            if (warning_at (input_location, OPT_Wmissing_field_initializers,
diff --git gcc/testsuite/gcc.dg/pr63480.c gcc/testsuite/gcc.dg/pr63480.c
index e69de29..89e2586 100644
--- gcc/testsuite/gcc.dg/pr63480.c
+++ gcc/testsuite/gcc.dg/pr63480.c
@@ -0,0 +1,14 @@
+/* PR c/63480 */
+/* { dg-do compile } */
+/* { dg-options "-Wmissing-field-initializers" } */
+
+/* Test that we don't warn about initializing with { }.  */
+
+struct S { int a, b, c; } s = { };
+
+void
+foo (void)
+{
+  struct S s = { }; 
+  struct S s2 = (struct S){ };
+}

        Marek