Fix unsigned type overflow in memory report.

2019-10-29  Martin Liska  <mliska@suse.cz>

	* ggc-common.c: One can't subtract unsigned types
	in compare function.

From-SVN: r277560

gcc/ChangeLog

 2019-10-29  Martin Liska  <mliska@suse.cz>
 
+	* ggc-common.c: One can't subtract unsigned types
+	in compare function.
+
+2019-10-29  Martin Liska  <mliska@suse.cz>
+
 	* cgraphunit.c (symbol_table::compile): Pass
 	title as dump_memory_report argument.
 	* toplev.c (dump_memory_report):  New argument.

gcc/ggc-common.c

@@ -928,10 +928,13 @@ public:
   static int
   compare (const void *first, const void *second)
   {
-    const mem_pair_t f = *(const mem_pair_t *)first;
-    const mem_pair_t s = *(const mem_pair_t *)second;
+    const mem_pair_t mem1 = *(const mem_pair_t *) first;
+    const mem_pair_t mem2 = *(const mem_pair_t *) second;
 
-    return s.second->get_balance () - f.second->get_balance ();
+    size_t balance1 = mem1.second->get_balance ();
+    size_t balance2 = mem2.second->get_balance ();
+
+    return balance1 == balance2 ? 0 : (balance1 < balance2 ? 1 : -1);
   }
 
   /* Dump header with NAME.  */