MVM_fixed_size_realloc_at_safepoint.patch

diff --git src/core/fixedsizealloc.c src/core/fixedsizealloc.c
index d0b568de3..2c7750f36 100644
--- src/core/fixedsizealloc.c
+++ src/core/fixedsizealloc.c
@@ -10,7 +10,7 @@
  * behavior. */
 
 /* Turn this on to switch to a mode where we debug by size. */
-#define FSA_SIZE_DEBUG 0
+#define FSA_SIZE_DEBUG 1
 #if FSA_SIZE_DEBUG
 typedef struct {
     size_t alloc_size;
@@ -246,10 +246,10 @@ void * MVM_fixed_size_realloc(MVMThreadContext *tc, MVMFixedSizeAlloc *al, void
 /* Reallocs a piece of memory to the specified size, using the FSA. */
 void * MVM_fixed_size_realloc_at_safepoint(MVMThreadContext *tc, MVMFixedSizeAlloc *al, void * p, size_t old_bytes, size_t new_bytes) {
 #if FSA_SIZE_DEBUG
-    MVMFixedSizeAllocDebug *new_p = MVM_fixed_size_alloc(tc, al, new_bytes);
-    memcpy(new_p, (char *)p, new_bytes > old_bytes ? old_bytes : new_bytes);
+    MVMFixedSizeAllocDebug *new_p = (MVMFixedSizeAllocDebug *)((char *)MVM_fixed_size_alloc(tc, al, new_bytes) - 8);
+    memcpy(new_p->memory, (char *)p, new_bytes > old_bytes ? old_bytes : new_bytes);
     MVM_fixed_size_free_at_safepoint(tc, al, old_bytes, p);
-    return new_p;
+    return &(new_p->memory);
 #else
     MVMuint32 old_bin = bin_for(old_bytes);
     MVMuint32 new_bin = bin_for(new_bytes);