PR c++/87519 - bogus warning with -Wsign-conversion.

	* typeck.c (cp_build_binary_op): Use same_type_p instead of comparing
	the types directly.

	* g++.dg/warn/Wsign-conversion-5.C: New test.

From-SVN: r274211

gcc/cp/ChangeLog

 2019-08-08  Marek Polacek  <polacek@redhat.com>
 
+	PR c++/87519 - bogus warning with -Wsign-conversion.
+	* typeck.c (cp_build_binary_op): Use same_type_p instead of comparing
+	the types directly.
+
 	* constexpr.c (inline_asm_in_constexpr_error): New.
 	(cxx_eval_constant_expression) <case ASM_EXPR>: Call it.
 	(potential_constant_expression_1) <case ASM_EXPR>: Likewise.

gcc/cp/typeck.c

@@ -5509,9 +5509,9 @@ cp_build_binary_op (const op_location_t &location,
   if (! converted)
     {
       warning_sentinel w (warn_sign_conversion, short_compare);
-      if (TREE_TYPE (op0) != result_type)
+      if (!same_type_p (TREE_TYPE (op0), result_type))
 	op0 = cp_convert_and_check (result_type, op0, complain);
-      if (TREE_TYPE (op1) != result_type)
+      if (!same_type_p (TREE_TYPE (op1), result_type))
 	op1 = cp_convert_and_check (result_type, op1, complain);
 
       if (op0 == error_mark_node || op1 == error_mark_node)

gcc/testsuite/ChangeLog

 2019-08-08  Marek Polacek  <polacek@redhat.com>
 
+	PR c++/87519 - bogus warning with -Wsign-conversion.
+	* g++.dg/warn/Wsign-conversion-5.C: New test.
+
 	* g++.dg/cpp2a/inline-asm3.C: New test.
 
 2019-08-07  Steven G. Kargl  <kargl@gcc.gnu.org>

gcc/testsuite/g++.dg/warn/Wsign-conversion-5.C

+// PR c++/87519 - bogus warning with -Wsign-conversion.
+// { dg-options "-Wsign-conversion" }
+
+typedef unsigned long int uint64_t;
+
+void f(unsigned long int a, int q)
+{
+  a += a + q; // { dg-warning "may change the sign" }
+
+  // Explicit cast should disable the warning.
+  a = a + static_cast<uint64_t>(q);
+  a = a + (uint64_t) q;
+  a = a + uint64_t(q);
+  a = a + static_cast<const uint64_t>(q);
+  a = a + (const uint64_t) q;
+  a = a + static_cast<unsigned long int>(q);
+  a = a + static_cast<const unsigned long int>(q);
+}