Decide between memory unmapping and mprotect-based dirty bits at runtime

* allchblk.c [USE_MUNMAP && MPROTECT_VDB] (GC_has_unmapped_memory): New
function.
* include/private/gcconfig.h [USE_MUNMAP] (MPROTECT_VDB): Do not
undefine unless GWW_VDB; update comment.
* os_dep.c [MPROTECT_VDB && USE_MUNMAP] (GC_has_unmapped_memory,
GC_mprotect_dirty_init): Declare function.
* os_dep.c [MPROTECT_VDB && USE_MUNMAP] (GC_dirty_init): Ensure
mprotect-based virtual dirty bits and memory unmapping are not both
turned on (disable on of them and call WARN with the appropriate
message), and call GC_mprotect_dirty_init (unless memory unmapping is
requested or some pages are already unmapped).
* os_dep.c [MPROTECT_VDB && !USE_MUNMAP] (GC_mprotect_dirty_init):
Define as a macro (to GC_dirty_init).
* os_dep.c [MPROTECT_VDB] (GC_dirty_init): Rename to
GC_mprotect_dirty_init.

1 files changed, 18 insertions, 0 deletions

diff --git a/allchblk.c b/allchblk.c
index 90331dc8..8b84aab8 100644
--- a/allchblk.c
+++ b/allchblk.c
@@ -417,6 +417,24 @@ GC_INNER void GC_unmap_old(void)
     }
 }
 
+# ifdef MPROTECT_VDB
+    GC_INNER GC_bool GC_has_unmapped_memory(void)
+    {
+      int i;
+
+      for (i = 0; i <= N_HBLK_FLS; ++i) {
+        struct hblk * h;
+        hdr * hhdr;
+
+        for (h = GC_hblkfreelist[i]; h != NULL; h = hhdr -> hb_next) {
+          hhdr = HDR(h);
+          if (!IS_MAPPED(hhdr)) return TRUE;
+        }
+      }
+      return FALSE;
+    }
+# endif /* MPROTECT_VDB */
+
 /* Merge all unmapped blocks that are adjacent to other free            */
 /* blocks.  This may involve remapping, since all blocks are either     */
 /* fully mapped or fully unmapped.                                      */