Make comparisons to the lowest heap boundary strict

* alloc.c (GC_expand_hp_inner): Subtract sizeof(word) from new_limit
(for the case when comparing to GC_least_plausible_heap_addr).
* backgraph.c [MAKE_BACK_GRAPH] (add_back_edges): Compare current to
GC_least_real_heap_addr and GC_greatest_real_heap_addr (instead of
GC_least_plausible_heap_addr and GC_greatest_plausible_heap_addr).
* malloc.c [GC_ASSERTIONS] (GC_malloc_kind_global): Likewise.
* include/gc/gc_mark.h (GC_MARK_AND_PUSH): Replace greater-or-equal to
strictly greater when comparing to GC_least_plausible_heap_addr.
* include/private/gc_pmark.h (GC_PUSH_ONE_STACK, GC_PUSH_ONE_HEAP):
Likewise.
* include/private/gc_priv.h [MAKE_BACK_GRAPH] (SET_REAL_HEAP_BOUNDS,
GC_least_real_heap_addr, GC_greatest_real_heap_addr): Define.
* mark.c (GC_mark_from, GC_push_all): Add dummy "| GC_DS_LENGTH" when
storing length to mse_descr.w.
* mark.c (GC_mark_from): Replace greater-or-equal to strictly greater
when comparing to least_ha variable.
* typd_mlc.c (GC_typed_mark_proc): Likewise.
* mark.c [GC_DS_TAGS>ALIGNMENT-1] (GC_push_all): Simplify code to
round up length.

3 files changed, 7 insertions, 6 deletions

diff --git a/include/gc/gc_mark.h b/include/gc/gc_mark.h
index acec052b..330d6f4b 100644
--- a/include/gc/gc_mark.h
+++ b/include/gc/gc_mark.h
@@ -158,7 +158,7 @@ GC_API struct GC_ms_entry * GC_CALL GC_mark_and_push(void * /* obj */,
                                 void ** /* src */);
 
 #define GC_MARK_AND_PUSH(obj, msp, lim, src) \
-          ((GC_word)(obj) >= (GC_word)GC_least_plausible_heap_addr \
+          ((GC_word)(obj) > (GC_word)GC_least_plausible_heap_addr \
            && (GC_word)(obj) < (GC_word)GC_greatest_plausible_heap_addr ? \
            GC_mark_and_push(obj, msp, lim, src) : (msp))
 
diff --git a/include/private/gc_pmark.h b/include/private/gc_pmark.h
index 286bf179..bbee8729 100644
--- a/include/private/gc_pmark.h
+++ b/include/private/gc_pmark.h
@@ -380,12 +380,12 @@ GC_INLINE mse * GC_push_contents_hdr(ptr_t current, mse * mark_stack_top,
     /* Try both the raw version and the fixed up one.   */
 # define GC_PUSH_ONE_STACK(p, source) \
     do { \
-      if ((word)(p) >= (word)GC_least_plausible_heap_addr \
+      if ((word)(p) > (word)GC_least_plausible_heap_addr \
           && (word)(p) < (word)GC_greatest_plausible_heap_addr) { \
          PUSH_ONE_CHECKED_STACK(p, source); \
       } \
       FIXUP_POINTER(p); \
-      if ((word)(p) >= (word)GC_least_plausible_heap_addr \
+      if ((word)(p) > (word)GC_least_plausible_heap_addr \
           && (word)(p) < (word)GC_greatest_plausible_heap_addr) { \
          PUSH_ONE_CHECKED_STACK(p, source); \
       } \
@@ -393,7 +393,7 @@ GC_INLINE mse * GC_push_contents_hdr(ptr_t current, mse * mark_stack_top,
 #else /* !NEED_FIXUP_POINTER */
 # define GC_PUSH_ONE_STACK(p, source) \
     do { \
-      if ((word)(p) >= (word)GC_least_plausible_heap_addr \
+      if ((word)(p) > (word)GC_least_plausible_heap_addr \
           && (word)(p) < (word)GC_greatest_plausible_heap_addr) { \
          PUSH_ONE_CHECKED_STACK(p, source); \
       } \
@@ -404,7 +404,7 @@ GC_INLINE mse * GC_push_contents_hdr(ptr_t current, mse * mark_stack_top,
 #define GC_PUSH_ONE_HEAP(p,source,mark_stack_top) \
     do { \
       FIXUP_POINTER(p); \
-      if ((word)(p) >= (word)GC_least_plausible_heap_addr \
+      if ((word)(p) > (word)GC_least_plausible_heap_addr \
           && (word)(p) < (word)GC_greatest_plausible_heap_addr) \
         mark_stack_top = GC_mark_and_push((void *)(p), mark_stack_top, \
                                 GC_mark_stack_limit, (void * *)(source)); \
diff --git a/include/private/gc_priv.h b/include/private/gc_priv.h
index 84bcc14c..dc442afb 100644
--- a/include/private/gc_priv.h
+++ b/include/private/gc_priv.h
@@ -1448,7 +1448,8 @@ struct _GC_arrays {
         /* obtained scratch area.                               */
         /* Used by GC_register_dynamic_libraries().             */
 # endif
-# if defined(GC_ASSERTIONS) || (defined(KEEP_BACK_PTRS) && ALIGNMENT == 1)
+# if defined(GC_ASSERTIONS) || defined(MAKE_BACK_GRAPH) \
+     || (defined(KEEP_BACK_PTRS) && ALIGNMENT == 1)
 #   define SET_REAL_HEAP_BOUNDS
 #   define GC_least_real_heap_addr GC_arrays._least_real_heap_addr
 #   define GC_greatest_real_heap_addr GC_arrays._greatest_real_heap_addr