gc: Clear the gap byte for the no-finalisers case.

jepler · jepler · commit 347046d1b986 · 2021-09-15T13:31:56.000-05:00
Signed-off-by: Jeff Epler &lt;jepler@gmail.com&gt;
diff --git a/py/gc.c b/py/gc.c
@@ -90,18 +90,18 @@
 #define PTR_FROM_BLOCK(block) (((block) * BYTES_PER_BLOCK + (uintptr_t)MP_STATE_MEM(gc_pool_start)))
 #define ATB_FROM_BLOCK(bl) ((bl) / BLOCKS_PER_ATB)
 
-#if MICROPY_ENABLE_FINALISER
-// FTB = finaliser table byte
-// if set, then the corresponding block may have a finaliser
-
-#define BLOCKS_PER_FTB (8)
-
 // After the ATB, there must be a byte filled with AT_FREE so that gc_mark_tree
 // cannot erroneously conclude that a block extends past the end of the GC heap
 // due to bit patterns in the FTB (or first block, if finalizers are disabled)
 // being interpreted as AT_TAIL.
 #define ALLOC_TABLE_GAP_BYTE (1)
 
+#if MICROPY_ENABLE_FINALISER
+// FTB = finaliser table byte
+// if set, then the corresponding block may have a finaliser
+
+#define BLOCKS_PER_FTB (8)
+
 #define FTB_GET(block) ((MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] >> ((block) & 7)) & 1)
 #define FTB_SET(block) do { MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] |= (1 << ((block) & 7)); } while (0)
 #define FTB_CLEAR(block) do { MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] &= (~(1 << ((block) & 7))); } while (0)
@@ -154,7 +154,7 @@ void gc_init(void *start, void *end) {
     memset(MP_STATE_MEM(gc_finaliser_table_start), 0, gc_finaliser_table_byte_len + gc_alloc_table_byte_len + ALLOC_TABLE_GAP_BYTE);
     #else
     // clear ATBs
-    memset(MP_STATE_MEM(gc_alloc_table_start), 0, MP_STATE_MEM(gc_alloc_table_byte_len));
+    memset(MP_STATE_MEM(gc_alloc_table_start), 0, MP_STATE_MEM(gc_alloc_table_byte_len) + ALLOC_TABLE_GAP_BYTE);
     #endif
 
     // set last free ATB index to start of heap
