re PR c++/86738 (gcc 8.2: Internal compiler error memcpy)

	PR c++/86738
	* constexpr.c (cxx_eval_binary_expression): For arithmetics involving
	NULL pointer set *non_constant_p to true.
	(cxx_eval_component_reference): For dereferencing of a NULL pointer,
	set *non_constant_p to true and return t.

	* g++.dg/opt/pr86738.C: New test.

From-SVN: r263390

gcc/cp/ChangeLog

+2018-08-08  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/86738
+	* constexpr.c (cxx_eval_binary_expression): For arithmetics involving
+	NULL pointer set *non_constant_p to true.
+	(cxx_eval_component_reference): For dereferencing of a NULL pointer,
+	set *non_constant_p to true and return t.
+
 2018-08-07  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/59480, DR 136

gcc/cp/constexpr.c

@@ -2082,6 +2082,7 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t,
     {
       if (!ctx->quiet)
 	error ("arithmetic involving a null pointer in %qE", lhs);
+      *non_constant_p = true;
       return t;
     }
   else if (code == POINTER_PLUS_EXPR)
@@ -2522,9 +2523,13 @@ cxx_eval_component_reference (const constexpr_ctx *ctx, tree t,
 					     lval,
 					     non_constant_p, overflow_p);
   if (INDIRECT_REF_P (whole)
-      && integer_zerop (TREE_OPERAND (whole, 0))
-      && !ctx->quiet)
-    error ("dereferencing a null pointer in %qE", orig_whole);
+      && integer_zerop (TREE_OPERAND (whole, 0)))
+    {
+      if (!ctx->quiet)
+	error ("dereferencing a null pointer in %qE", orig_whole);
+      *non_constant_p = true;
+      return t;
+    }
 
   if (TREE_CODE (whole) == PTRMEM_CST)
     whole = cplus_expand_constant (whole);

gcc/testsuite/ChangeLog

+2018-08-08  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/86738
+	* g++.dg/opt/pr86738.C: New test.
+
 2018-08-07  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR target/86838

gcc/testsuite/g++.dg/opt/pr86738.C

+// PR c++/86738
+// { dg-do compile }
+
+struct S { int s; };
+unsigned char a[20];
+unsigned char *p = &a[(__UINTPTR_TYPE__) &((S *) 0)->s];
+
+void
+foo ()
+{
+  __builtin_memcpy (&a[15], &a[(__UINTPTR_TYPE__) &((S *) 0)->s], 2);
+}