Do not update scratch_last_end_ptr unless used by reg dynamic libraries

(refactoring)

* headers.c (GC_scratch_alloc): Do not update GC_scratch_last_end_ptr
unless USE_SCRATCH_LAST_END_PTR; add TODO item.
* include/private/gc_priv.h [IRIX5 || USE_PROC_FOR_LIBRARIES && !LINUX]
(USE_SCRATCH_LAST_END_PTR): Define macro.
* include/private/gc_priv.h (_GC_arrays._scratch_last_end_ptr,
GC_scratch_last_end_ptr): Do define unless USE_SCRATCH_LAST_END_PTR;
refine comment.

2 files changed, 17 insertions, 8 deletions

diff --git a/headers.c b/headers.c
index 375194c9..6247c438 100644
--- a/headers.c
+++ b/headers.c
@@ -122,11 +122,13 @@ GC_INNER ptr_t GC_scratch_alloc(size_t bytes)
             GC_add_to_our_memory(result, bytes_to_get);
             /* Undo scratch free area pointer update; get memory directly. */
             GC_scratch_free_ptr -= bytes;
-            if (result != NULL) {
+#           ifdef USE_SCRATCH_LAST_END_PTR
+              if (result != NULL) {
                 /* Update end point of last obtained area (needed only  */
                 /* by GC_register_dynamic_libraries for some targets).  */
                 GC_scratch_last_end_ptr = result + bytes;
-            }
+              }
+#           endif
             return result;
         }
 
@@ -141,14 +143,19 @@ GC_INNER ptr_t GC_scratch_alloc(size_t bytes)
             bytes_to_get = ROUNDUP_PAGESIZE_IF_MMAP(bytes);
             result = (ptr_t)GET_MEM(bytes_to_get);
             GC_add_to_our_memory(result, bytes_to_get);
-            if (result != NULL)
+#           ifdef USE_SCRATCH_LAST_END_PTR
+              if (result != NULL)
                 GC_scratch_last_end_ptr = result + bytes;
+#           endif
             return result;
         }
+        /* TODO: some amount of unallocated space may remain unused forever */
         /* Update scratch area pointers and retry.      */
         GC_scratch_free_ptr = result;
         GC_scratch_end_ptr = GC_scratch_free_ptr + bytes_to_get;
-        GC_scratch_last_end_ptr = GC_scratch_end_ptr;
+#       ifdef USE_SCRATCH_LAST_END_PTR
+          GC_scratch_last_end_ptr = GC_scratch_end_ptr;
+#       endif
     }
 }
 
diff --git a/include/private/gc_priv.h b/include/private/gc_priv.h
index 1c35c98b..fac4a7ce 100644
--- a/include/private/gc_priv.h
+++ b/include/private/gc_priv.h
@@ -1399,11 +1399,14 @@ struct _GC_arrays {
   hdr *_hdr_free_list;
   ptr_t _scratch_end_ptr;
         /* GC_scratch_end_ptr is end point of the current scratch area. */
-  ptr_t _scratch_last_end_ptr;
+# if defined(IRIX5) || (defined(USE_PROC_FOR_LIBRARIES) && !defined(LINUX))
+#   define USE_SCRATCH_LAST_END_PTR
+#   define GC_scratch_last_end_ptr GC_arrays._scratch_last_end_ptr
+    ptr_t _scratch_last_end_ptr;
         /* GC_scratch_last_end_ptr is the end point of the last */
         /* obtained scratch area.                               */
-        /* Used by headers.c, and can easily appear to point to */
-        /* heap.  Also used by GC_register_dynamic_libraries(). */
+        /* Used by GC_register_dynamic_libraries().             */
+# endif
   mse *_mark_stack;
         /* Limits of stack for GC_mark routine.  All ranges     */
         /* between GC_mark_stack (incl.) and GC_mark_stack_top  */
@@ -1652,7 +1655,6 @@ GC_API_PRIV GC_FAR struct _GC_arrays GC_arrays;
 #define GC_scratch_free_ptr GC_arrays._scratch_free_ptr
 #define GC_hdr_free_list GC_arrays._hdr_free_list
 #define GC_scratch_end_ptr GC_arrays._scratch_end_ptr
-#define GC_scratch_last_end_ptr GC_arrays._scratch_last_end_ptr
 #define GC_size_map GC_arrays._size_map
 #define GC_static_roots GC_arrays._static_roots
 #define GC_top_index GC_arrays._top_index