Add in a header flag for whether we turn on the precise GC or not.

include/parrot/gc_api.h

@@ -11,6 +11,14 @@
 
 #include "parrot/parrot.h"
 
+/* Flag to turn on precise GC
+    0 = no precise GC (use only stack walking)
+    1 = precise GC + stack walking
+    2 = precise GC only (this is what we want)
+*/
+
+#define GC_USE_PRECISE 1
+
 /*
  * we need an alignment that is the same as malloc(3) have for
  * allocating Buffer items like FLOATVAL (double)
@@ -123,6 +131,8 @@ typedef struct __gc_anchor_storage {
     size_t elements;
 } gc_anchor_storage;
 
+#if GC_USE_PRECISE != 0
+
 #define GC_SETUP_ANCHOR_STORAGE(i, n) { \
         const size_t __num_slots = n; \
         const size_t __pmc_storage_size = (n) * sizeof (PMC *); \
@@ -159,6 +169,15 @@ typedef struct __gc_anchor_storage {
         __anchor_storage[(n)] = (p); \
     }
 
+#else
+
+#define GC_SETUP_ANCHOR_STORAGE(i, n)
+#define GC_CLEANUP_ANCHOR_STORAGE(i)
+#define GC_GET_ANCHOR_STORAGE(n, p)
+#define GC_SET_ANCHOR_STORAGE(n, p)
+
+#endif
+
 
 /* HEADERIZER BEGIN: src/gc/api.c */
 /* Don't modify between HEADERIZER BEGIN / HEADERIZER END.  Your changes will be lost. */

src/gc/mark_sweep.c

@@ -178,10 +178,13 @@ Parrot_gc_trace_root(PARROT_INTERP,
             = interp->iglobals;
     }
 
+#if GC_USE_PRECISE != 2
 
     if (trace == GC_TRACE_FULL)
         trace_system_areas(interp, mem_pools);
 
+#endif
+
     mark_interp(interp);
 
     /* quick check to see if we have already marked all impatient PMCs. If we
@@ -257,6 +260,8 @@ mark_interp(PARROT_INTERP)
     if (interp->parent_interpreter)
         mark_interp(interp->parent_interpreter);
 
+#if GC_USE_PRECISE != 0
+
     {
         gc_anchor_storage * s = interp->gc_anchor_storage;
         while(s) {
@@ -271,6 +276,8 @@ mark_interp(PARROT_INTERP)
             s = s->prev;
         }
     }
+
+#endif
 }