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

2019-07-08  Matthew Beliveau  <mbelivea@redhat.com>
	
PR c++/90590
	* c-warn.c (c_do_switch_warnings): Suppress warning for enumerators
	with reserved names that are in a system header.

	* c-c++-common/pr90590-1.c: New test.
	* c-c++-common/pr90590-1.h: New test.
	* c-c++-common/pr90590-2.c: New test.
	* c-c++-common/pr90590-2.h: New test.

diff --git gcc/c-family/c-warn.c gcc/c-family/c-warn.c
index b5d09e761d7..56ad23dd29c 100644
--- gcc/c-family/c-warn.c
+++ gcc/c-family/c-warn.c
@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gcc-rich-location.h"
 #include "gimplify.h"
 #include "c-family/c-indentation.h"
+#include "c-family/c-spellcheck.h"
 #include "calls.h"
 #include "stor-layout.h"
 
@@ -1592,8 +1593,12 @@ c_do_switch_warnings (splay_tree cases, location_t switch_location,
   for (chain = TYPE_VALUES (type); chain; chain = TREE_CHAIN (chain))
     {
       tree value = TREE_VALUE (chain);
+      tree decl = NULL_TREE;
       if (TREE_CODE (value) == CONST_DECL)
-	value = DECL_INITIAL (value);
+	{
+	  decl = value;
+	  value = DECL_INITIAL (value);
+	}
       node = splay_tree_lookup (cases, (splay_tree_key) value);
       if (node)
 	{
@@ -1628,6 +1633,19 @@ c_do_switch_warnings (splay_tree cases, location_t switch_location,
       if (cond && tree_int_cst_compare (cond, value))
 	continue;
 
+      /* If the enumerator is defined in a system header and uses a reserved
+	 name, then we continue to avoid throwing a warning.  */
+      if (decl == NULL_TREE)
+	decl = lookup_name (TREE_PURPOSE (chain));
+      if (decl && TREE_CODE (decl) == CONST_DECL)
+	{
+	  const char *name = IDENTIFIER_POINTER (DECL_NAME (decl));
+	  location_t loc = DECL_SOURCE_LOCATION (decl);
+	  if (in_system_header_at (loc)
+	      && name_reserved_for_implementation_p (name))
+	    continue;
+	}
+
       /* If there is a default_node, the only relevant option is
 	 Wswitch-enum.  Otherwise, if both are enabled then we prefer
 	 to warn using -Wswitch because -Wswitch is enabled by -Wall
diff --git gcc/testsuite/c-c++-common/pr90590-1.c gcc/testsuite/c-c++-common/pr90590-1.c
new file mode 100644
index 00000000000..4997a3082d5
--- /dev/null
+++ gcc/testsuite/c-c++-common/pr90590-1.c
@@ -0,0 +1,15 @@
+// PR c++/90590
+// { dg-options -Wswitch }
+#include "pr90590-1.h"
+
+void
+g ()
+{
+  enum E e = _A;
+  switch (e) // { dg-bogus "enumeration value '_C' not handled in switch" }
+    {
+    case _A:
+    case _B:
+      break;
+    }
+}
diff --git gcc/testsuite/c-c++-common/pr90590-1.h gcc/testsuite/c-c++-common/pr90590-1.h
new file mode 100644
index 00000000000..22f1a7d5d52
--- /dev/null
+++ gcc/testsuite/c-c++-common/pr90590-1.h
@@ -0,0 +1,2 @@
+#pragma GCC system_header
+enum E { _A, _B, _C };
diff --git gcc/testsuite/c-c++-common/pr90590-2.c gcc/testsuite/c-c++-common/pr90590-2.c
new file mode 100644
index 00000000000..8aa65cf0afd
--- /dev/null
+++ gcc/testsuite/c-c++-common/pr90590-2.c
@@ -0,0 +1,8 @@
+#include "pr90590-2.h"
+
+void
+fn ()
+{
+  switch (c.b) // { dg-bogus "enumeration value" }
+    ;
+}
diff --git gcc/testsuite/c-c++-common/pr90590-2.h gcc/testsuite/c-c++-common/pr90590-2.h
new file mode 100644
index 00000000000..e4f8635576f
--- /dev/null
+++ gcc/testsuite/c-c++-common/pr90590-2.h
@@ -0,0 +1,4 @@
+#pragma GCC system_header
+struct {
+  enum { _A } b;
+} c;