Do not prohibit zero proc argument in GC_register_disclaim_proc

(a cherry-pick of commit d4c4a7ba5 from 'master')

* fnlz_mlc.c [ENABLE_DISCLAIM] (GC_register_disclaim_proc): Do not
check that proc is non-zero.
* include/gc_disclaim.h (GC_register_disclaim_proc): Remove
GC_ATTR_NONNULL(2) attribute.
* reclaim.c [ENABLE_DISCLAIM] (GC_disclaim_and_reclaim): Add assertion
that disclaim is non-zero.

3 files changed, 2 insertions, 2 deletions

diff --git a/fnlz_mlc.c b/fnlz_mlc.c
index bfbcf506..65210586 100644
--- a/fnlz_mlc.c
+++ b/fnlz_mlc.c
@@ -89,7 +89,6 @@ GC_API void GC_CALL GC_register_disclaim_proc(int kind, GC_disclaim_proc proc,
                                               int mark_unconditionally)
 {
     GC_ASSERT((unsigned)kind < MAXOBJKINDS);
-    GC_ASSERT(NONNULL_ARG_NOT_NULL(proc));
     if (!EXPECT(GC_find_leak, FALSE)) {
         GC_obj_kinds[kind].ok_disclaim_proc = proc;
         GC_obj_kinds[kind].ok_mark_unconditionally =
diff --git a/include/gc_disclaim.h b/include/gc_disclaim.h
index 6394b05e..785182b5 100644
--- a/include/gc_disclaim.h
+++ b/include/gc_disclaim.h
@@ -43,7 +43,7 @@ typedef int (GC_CALLBACK * GC_disclaim_proc)(void * /*obj*/);
 /* No-op in the leak-finding mode.                                      */
 GC_API void GC_CALL GC_register_disclaim_proc(int /*kind*/,
                                 GC_disclaim_proc /*proc*/,
-                                int /*mark_from_all*/) GC_ATTR_NONNULL(2);
+                                int /*mark_from_all*/);
 
 /* The finalizer closure used by GC_finalized_malloc.                   */
 struct GC_finalizer_closure {
diff --git a/reclaim.c b/reclaim.c
index 72244d80..22b489ae 100644
--- a/reclaim.c
+++ b/reclaim.c
@@ -239,6 +239,7 @@ STATIC ptr_t GC_reclaim_uninit(struct hblk *hbp, hdr *hhdr, word sz,
     struct obj_kind *ok = &GC_obj_kinds[hhdr->hb_obj_kind];
     int (GC_CALLBACK *disclaim)(void *) = ok->ok_disclaim_proc;
 
+    GC_ASSERT(disclaim != 0);
 #   ifndef THREADS
       GC_ASSERT(sz == hhdr -> hb_sz);
 #   endif