Prefer signed when testing for signed overflow

* src/alloc.c (free_cons):
* src/casefiddle.c (do_casify_multibyte_string):
* src/editfns.c (styled_format):
* src/image.c (png_load_body):
Use signed arguments to INT_MULTIPLY_WRAPV etc.  This doesn’t fix
any bugs, but GCC emits better code when all args are signed.
Also, this removes the need for an if in free_cons (Bug#37006).

1 files changed, 2 insertions, 3 deletions

diff --git a/src/alloc.c b/src/alloc.c
index d9022ac46c3..8227feadae5 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2542,9 +2542,8 @@ free_cons (struct Lisp_Cons *ptr)
   ptr->u.s.u.chain = cons_free_list;
   ptr->u.s.car = dead_object ();
   cons_free_list = ptr;
-  if (consing_until_gc <= 0)
-    consing_until_gc += sizeof *ptr;
-  else if (INT_ADD_WRAPV (consing_until_gc, sizeof *ptr, &consing_until_gc))
+  int incr = sizeof *ptr;
+  if (INT_ADD_WRAPV (consing_until_gc, incr, &consing_until_gc))
     consing_until_gc = OBJECT_CT_MAX;
   gcstat.total_free_conses++;
 }