Handle trailing arrays in ODR warning (PR lto/81440).

2018-01-23  Martin Liska  <mliska@suse.cz>

	PR lto/81440
	* lto-symtab.c (lto_symtab_merge): Handle and do not warn about
	trailing arrays at the end of a struct.
2018-01-23  Martin Liska  <mliska@suse.cz>

	PR lto/81440
	* gcc.dg/lto/pr81440.h: New test.
	* gcc.dg/lto/pr81440_0.c: New test.
	* gcc.dg/lto/pr81440_1.c: New test.

From-SVN: r256989

gcc/lto/ChangeLog

+2018-01-23  Martin Liska  <mliska@suse.cz>
+
+	PR lto/81440
+	* lto-symtab.c (lto_symtab_merge): Handle and do not warn about
+	trailing arrays at the end of a struct.
+
 2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>

gcc/lto/lto-symtab.c

@@ -352,18 +352,31 @@ lto_symtab_merge (symtab_node *prevailing, symtab_node *entry)
     return false;
 
   if (DECL_SIZE (decl) && DECL_SIZE (prevailing_decl)
-      && !tree_int_cst_equal (DECL_SIZE (decl), DECL_SIZE (prevailing_decl))
+      && !tree_int_cst_equal (DECL_SIZE (decl), DECL_SIZE (prevailing_decl)))
+      {
+	if (!DECL_COMMON (decl) && !DECL_EXTERNAL (decl))
+	  return false;
+
+	tree type = TREE_TYPE (decl);
+
+	/* For record type, check for array at the end of the structure.  */
+	if (TREE_CODE (type) == RECORD_TYPE)
+	  {
+	    tree field = TYPE_FIELDS (type);
+	    while (DECL_CHAIN (field) != NULL_TREE)
+	      field = DECL_CHAIN (field);
+
+	    return TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE;
+	  }
       /* As a special case do not warn about merging
 	 int a[];
 	 and
 	 int a[]={1,2,3};
 	 here the first declaration is COMMON
 	 and sizeof(a) == sizeof (int).  */
-      && ((!DECL_COMMON (decl) && !DECL_EXTERNAL (decl))
-	  || TREE_CODE (TREE_TYPE (decl)) != ARRAY_TYPE
-	  || TYPE_SIZE (TREE_TYPE (decl))
-	     != TYPE_SIZE (TREE_TYPE (TREE_TYPE (decl)))))
-    return false;
+	else if (TREE_CODE (type) == ARRAY_TYPE)
+	  return (TYPE_SIZE (decl) == TYPE_SIZE (TREE_TYPE (type)));
+      }
 
   return true;
 }

gcc/testsuite/ChangeLog

+2018-01-23  Martin Liska  <mliska@suse.cz>
+
+	PR lto/81440
+	* gcc.dg/lto/pr81440.h: New test.
+	* gcc.dg/lto/pr81440_0.c: New test.
+	* gcc.dg/lto/pr81440_1.c: New test.
+
 2018-01-23  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/83988

gcc/testsuite/gcc.dg/lto/pr81440.h

+typedef struct {
+  int i;
+  int ints[];
+} struct_t;

gcc/testsuite/gcc.dg/lto/pr81440_0.c

+/* { dg-lto-do link } */
+
+#include "pr81440.h"
+
+extern struct_t my_struct;
+
+int main() {
+ return my_struct.ints[0];
+}

gcc/testsuite/gcc.dg/lto/pr81440_1.c

+#include "pr81440.h"
+
+struct_t my_struct = {
+ 20,
+ { 1, 2 }
+};