Use ‘const’ to clarify GC marking

Add ‘const’ to make the GC marking code a bit clearer.
This can also help the compiler in some cases, I think because
GCC can now determine more often that the value of a static C
variable can be cached when its address is now converted to
‘Lisp Object const *’ before escaping.
* src/alloc.c (staticvec, mark_maybe_objects, mark_memory)
(mark_stack, staticpro, mark_object_root_visitor)
(garbage_collect_1):
* src/pdumper.c (dump_ptr_referrer, dump_emacs_reloc_to_lv)
(dump_emacs_reloc_to_emacs_ptr_raw, dump_root_visitor):
* src/lisp.h (vcopy, struct gc_root_visitor):
* src/sysdep.c (stack_overflow):
* src/thread.c (mark_one_thread):
* src/thread.h (struct thread_state):
Use pointer-to-const instead of plain pointer in some
GC-related places where either will do.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/thread.c b/src/thread.c
index 33d113295ba..59e5b6617e3 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -617,7 +617,7 @@ static void
 mark_one_thread (struct thread_state *thread)
 {
   /* Get the stack top now, in case mark_specpdl changes it.  */
-  void *stack_top = thread->stack_top;
+  void const *stack_top = thread->stack_top;
 
   mark_specpdl (thread->m_specpdl, thread->m_specpdl_ptr);