diff --git a/bdw.h b/bdw.h
index 21691ade8..07ba9d7c9 100644
--- a/bdw.h
+++ b/bdw.h
@@ -278,9 +278,7 @@ static void* gc_call_without_gc(struct mutator *mut,
   return GC_do_blocking(f, data);
 }
 
-static inline void print_start_gc_stats(struct heap *heap) {
-}
-static inline void print_end_gc_stats(struct heap *heap) {
+static void gc_print_stats(struct heap *heap) {
   printf("Completed %ld collections\n", (long)GC_get_gc_no());
   printf("Heap size is %ld\n", (long)GC_get_heap_size());
 }
diff --git a/gc-api.h b/gc-api.h
index df865025f..86bde3aa4 100644
--- a/gc-api.h
+++ b/gc-api.h
@@ -43,6 +43,7 @@ GC_API_ struct mutator* gc_init_for_thread(uintptr_t *stack_base,
 GC_API_ void gc_finish_for_thread(struct mutator *mut);
 GC_API_ void* gc_call_without_gc(struct mutator *mut, void* (*f)(void*),
                                  void *data) GC_NEVER_INLINE;
+GC_API_ void gc_print_stats(struct heap *heap);
 
 enum gc_allocator_kind {
   GC_ALLOCATOR_INLINE_BUMP_POINTER,
diff --git a/mt-gcbench.c b/mt-gcbench.c
index 3d7ae8933..00f1d7e1a 100644
--- a/mt-gcbench.c
+++ b/mt-gcbench.c
@@ -430,7 +430,6 @@ int main(int argc, char *argv[]) {
 
   printf("Garbage Collector Test\n");
   printf(" Live storage will peak at %zd bytes.\n\n", heap_max_live);
-  print_start_gc_stats(heap);
 
   unsigned long start = current_time();
         
@@ -456,5 +455,5 @@ int main(int argc, char *argv[]) {
   }
   
   printf("Completed in %.3f msec\n", elapsed_millis(start));
-  print_end_gc_stats(heap);
+  gc_print_stats(heap);
 }
diff --git a/quads.c b/quads.c
index 968c64163..0b26c5476 100644
--- a/quads.c
+++ b/quads.c
@@ -149,8 +149,6 @@ int main(int argc, char *argv[]) {
 
   PUSH_HANDLE(mut, quad);
 
-  print_start_gc_stats(heap);
-
   printf("Making quad tree of depth %zu (%zu nodes).  Total size %.3fGB.\n",
          depth, nquads, (nquads * sizeof(Quad)) / 1e9);
   unsigned long start = current_time();
@@ -176,7 +174,7 @@ int main(int argc, char *argv[]) {
   print_elapsed("allocation loop", garbage_start);
   print_elapsed("quads test", gc_start);
 
-  print_end_gc_stats(heap);
+  gc_print_stats(heap);
 
   POP_HANDLE(mut);
   return 0;
diff --git a/semi-inline.h b/semi-inline.h
new file mode 100644
index 000000000..9a8342fd4
--- /dev/null
+++ b/semi-inline.h
@@ -0,0 +1,54 @@
+#ifndef SEMI_INLINE_H
+#define SEMI_INLINE_H
+
+#include "gc-api.h"
+
+static const uintptr_t GC_ALIGNMENT = 8;
+static const size_t GC_LARGE_OBJECT_THRESHOLD = 8192;
+
+static inline enum gc_allocator_kind gc_allocator_kind(void) {
+  return GC_ALLOCATOR_INLINE_BUMP_POINTER;
+}
+static inline size_t gc_allocator_small_granule_size(void) {
+  return GC_ALIGNMENT;
+}
+static inline size_t gc_allocator_large_threshold(void) {
+  return GC_LARGE_OBJECT_THRESHOLD;
+}
+
+static inline size_t gc_allocator_allocation_pointer_offset(void) {
+  return sizeof(uintptr_t) * 0;
+}
+static inline size_t gc_allocator_allocation_limit_offset(void) {
+  return sizeof(uintptr_t) * 1;
+}
+
+static inline size_t gc_allocator_freelist_offset(size_t size) {
+  abort();
+}
+
+static inline int gc_allocator_needs_clear(void) {
+  return 1;
+}
+
+static inline size_t gc_allocator_alloc_table_alignment(void) {
+  return 0;
+}
+static inline uint8_t gc_allocator_alloc_table_begin_pattern(void) {
+  abort();
+}
+static inline uint8_t gc_allocator_alloc_table_end_pattern(void) {
+  abort();
+}
+
+static inline enum gc_write_barrier_kind gc_small_write_barrier_kind(void) {
+  return GC_WRITE_BARRIER_NONE;
+}
+static inline size_t gc_small_write_barrier_card_table_alignment(void) {
+  abort();
+}
+static inline size_t gc_small_write_barrier_card_size(void) {
+  abort();
+}
+
+#endif // SEMI_INLINE_H
diff --git a/semi.h b/semi.h
index cb50e445c..90a42d05d 100644
--- a/semi.h
+++ b/semi.h
@@ -5,6 +5,7 @@
 #include <sys/mman.h>
 #include <unistd.h>
 
+#include "semi-inline.h"
 #include "large-object-space.h"
 #include "precise-roots.h"
 
@@ -29,48 +30,11 @@ struct mutator {
   struct handle *roots;
 };
 
-static const uintptr_t ALIGNMENT = 8;
-static const size_t LARGE_OBJECT_THRESHOLD = 8192;
 
 static inline void clear_memory(uintptr_t addr, size_t size) {
   memset((char*)addr, 0, size);
 }
 
-static inline enum gc_allocator_kind gc_allocator_kind(void) {
-  return GC_ALLOCATOR_INLINE_BUMP_POINTER;
-}
-static inline size_t gc_allocator_small_granule_size(void) {
-  return ALIGNMENT;
-}
-static inline size_t gc_allocator_large_threshold(void) {
-  return LARGE_OBJECT_THRESHOLD;
-}
-
-static inline size_t gc_allocator_allocation_pointer_offset(void) {
-  return offsetof(struct semi_space, hp);
-}
-static inline size_t gc_allocator_allocation_limit_offset(void) {
-  return offsetof(struct semi_space, limit);
-}
-
-static inline size_t gc_allocator_freelist_offset(size_t size) {
-  abort();
-}
-
-static inline int gc_allocator_needs_clear(void) {
-  return 1;
-}
-
-static inline size_t gc_allocator_alloc_table_alignment(void) {
-  return 0;
-}
-static inline uint8_t gc_allocator_alloc_table_begin_pattern(void) {
-  abort();
-}
-static inline uint8_t gc_allocator_alloc_table_end_pattern(void) {
-  abort();
-}
-
 static inline struct heap* mutator_heap(struct mutator *mut) {
   return &mut->heap;
 }
@@ -135,14 +99,14 @@ static void* copy(struct semi_space *space, void *obj) {
   void *new_obj = (void*)space->hp;
   memcpy(new_obj, obj, size);
   *(uintptr_t*) obj = space->hp;
-  space->hp += align_up (size, ALIGNMENT);
+  space->hp += align_up (size, GC_ALIGNMENT);
   return new_obj;
 }
 
 static uintptr_t scan(struct heap *heap, uintptr_t grey) {
   size_t size;
   gc_trace_object((void*)grey, visit, heap, &size);
-  return grey + align_up(size, ALIGNMENT);
+  return grey + align_up(size, GC_ALIGNMENT);
 }
 
 static void* forward(struct semi_space *space, void *obj) {
@@ -237,7 +201,7 @@ static void* gc_allocate_small(struct mutator *mut, size_t size) {
   struct semi_space *space = mutator_semi_space(mut);
   while (1) {
     uintptr_t addr = space->hp;
-    uintptr_t new_hp = align_up (addr + size, ALIGNMENT);
+    uintptr_t new_hp = align_up (addr + size, GC_ALIGNMENT);
     if (space->limit < new_hp) {
       collect_for_alloc(mut, size);
       continue;
@@ -252,16 +216,6 @@ static inline void* gc_allocate_pointerless(struct mutator *mut, size_t size) {
   return gc_allocate(mut, size);
 }
 
-static inline enum gc_write_barrier_kind gc_small_write_barrier_kind(void) {
-  return GC_WRITE_BARRIER_NONE;
-}
-static inline size_t gc_small_write_barrier_card_table_alignment(void) {
-  abort();
-}
-static inline size_t gc_small_write_barrier_card_size(void) {
-  abort();
-}
-
 static int initialize_semi_space(struct semi_space *space, size_t size) {
   // Allocate even numbers of pages.
   size_t page_size = getpagesize();
@@ -348,8 +302,15 @@ static int parse_options(int argc, struct gc_option argv[],
   return 1;
 }
 
+#define GC_ASSERT_EQ(a, b) GC_ASSERT((a) == (b))
+
 static int gc_init(int argc, struct gc_option argv[],
                    struct heap **heap, struct mutator **mut) {
+  GC_ASSERT_EQ(gc_allocator_allocation_pointer_offset(),
+               offsetof(struct semi_space, hp));
+  GC_ASSERT_EQ(gc_allocator_allocation_limit_offset(),
+               offsetof(struct semi_space, limit));
+
   struct options options = { 0, };
   if (!parse_options(argc, argv, &options))
     return 0;
@@ -384,10 +345,7 @@ static void* gc_call_without_gc(struct mutator *mut, void* (*f)(void*),
   return f(data);
 }
 
-static inline void print_start_gc_stats(struct heap *heap) {
-}
-
-static inline void print_end_gc_stats(struct heap *heap) {
+static void gc_print_stats(struct heap *heap) {
   struct semi_space *space = heap_semi_space(heap);
   printf("Completed %ld collections\n", space->count);
   printf("Heap size is %zd\n", space->size);
diff --git a/whippet.h b/whippet.h
index 03c76349f..a070c0cb1 100644
--- a/whippet.h
+++ b/whippet.h
@@ -2097,10 +2097,7 @@ static void* gc_call_without_gc(struct mutator *mut,
   return ret;
 }
 
-static inline void print_start_gc_stats(struct heap *heap) {
-}
-
-static inline void print_end_gc_stats(struct heap *heap) {
+static void gc_print_stats(struct heap *heap) {
   printf("Completed %ld collections (%ld major)\n",
          heap->count, heap->count - heap->minor_count);
   printf("Heap size with overhead is %zd (%zu slabs)\n",