[C++ PATCH] PR c++/88380 - wrong-code with flexible array and NSDMI.

[Jason Merrill]

Here 'skipped' was set to -1 to force an explicit initializer for 'uninit'
before the initializer for 'initialized', and so we also tried to emit an
explicit initializer for the flexible array, for which build_zero_init
returns error_mark_node.  We should ignore flexarrays even when
skipped < 0.

Tested x86_64-pc-linux-gnu, applying to trunk.

	* typeck2.c (process_init_constructor_record): Skip flexarrays.
---
 gcc/cp/typeck2.c                     | 11 +++++++----
 gcc/testsuite/g++.dg/ext/flexary33.C | 13 +++++++++++++
 gcc/cp/ChangeLog                     |  5 +++++
 3 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/flexary33.C

diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index 4e4b1f03b7c..af56632c0fc 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -1602,12 +1602,15 @@ process_init_constructor_record (tree type, tree init, int nested, int flags,
 	      else
 		return PICFLAG_ERRONEOUS;
 	    }
+	  /* Do nothing for flexible array members since they need not have any
+	     elements.  Don't worry about 'skipped' because a flexarray has to
+	     be the last field.  */
+	  else if (TREE_CODE (fldtype) == ARRAY_TYPE && !TYPE_DOMAIN (fldtype))
+	    continue;
 
 	  /* Warn when some struct elements are implicitly initialized
-	     to zero.  However, avoid issuing the warning for flexible
-	     array members since they need not have any elements.  */
-	  if ((TREE_CODE (fldtype) != ARRAY_TYPE || TYPE_DOMAIN (fldtype))
-	      && (complain & tf_warning)
+	     to zero.  */
+	  if ((complain & tf_warning)
 	      && !EMPTY_CONSTRUCTOR_P (init))
 	    warning (OPT_Wmissing_field_initializers,
 		     "missing initializer for member %qD", field);
diff --git a/gcc/testsuite/g++.dg/ext/flexary33.C b/gcc/testsuite/g++.dg/ext/flexary33.C
new file mode 100644
index 00000000000..a12a6349621
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/flexary33.C
@@ -0,0 +1,13 @@
+// PR c++/88380
+// { dg-do compile { target c++14 } }
+// { dg-options "" }
+
+struct S {
+  char uninit;
+  char initialised = 11;
+  char variable[];
+};
+
+constexpr S p {};
+#define SA(X) static_assert((X),#X)
+SA(p.initialised == 11);
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 83d3ac94039..02e0845f1d7 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2019-02-19  Jason Merrill  <jason@redhat.com>
+
+	PR c++/88380 - wrong-code with flexible array and NSDMI.
+	* typeck2.c (process_init_constructor_record): Skip flexarrays.
+
 2019-02-20  will wray  <wjwray@gmail.com>
 
 	PR c++/88572 - wrong handling of braces on scalar init.

base-commit: 53ceddc9ed98b8717dc8ae7695459a76f16011cf
-- 
2.20.1