py: Take gc_pool_start out of bss section, to reclaim 1st block of heap.
diff --git a/py/gc.c b/py/gc.c
index c641e73..f808eef 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -58,7 +58,11 @@
#if MICROPY_ENABLE_FINALISER
STATIC byte *gc_finaliser_table_start;
#endif
-STATIC mp_uint_t *gc_pool_start;
+// We initialise gc_pool_start to a dummy value so it stays out of the bss
+// section. This makes sure we don't trace this pointer in a collect cycle.
+// If we did trace it, it would make the first block of the heap always
+// reachable, and hence we can never free that block.
+STATIC mp_uint_t *gc_pool_start = (void*)4;
STATIC mp_uint_t *gc_pool_end;
STATIC int gc_stack_overflow;
@@ -153,13 +157,6 @@
memset(gc_finaliser_table_start, 0, gc_finaliser_table_byte_len);
#endif
- // allocate first block because gc_pool_start points there and it will never
- // be freed, so allocating 1 block with null pointers will minimise memory loss
- ATB_FREE_TO_HEAD(0);
- for (int i = 0; i < WORDS_PER_BLOCK; i++) {
- gc_pool_start[i] = 0;
- }
-
// set last free ATB index to start of heap
gc_last_free_atb_index = 0;