Fix arithmetic overflow in GC consing count

* src/alloc.c (allow_garbage_collection):
Redo expression to avoid signed arithmetic overflow
in an intermediate expression when CONSING is negative.

diff --git a/src/alloc.c b/src/alloc.c
index c17bdb719a94247a0f8fe4ebaacb15172cd26580..5e089311a273788c3012834f69f2df0c6e41c206 100644 (file)
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -5498,7 +5498,7 @@ staticpro (Lisp_Object const *varaddress)
 static void
 allow_garbage_collection (intmax_t consing)
 {
-  consing_until_gc -= OBJECT_CT_MAX - consing;
+  consing_until_gc = consing - (OBJECT_CT_MAX - consing_until_gc);
   garbage_collection_inhibited--;
 }