atmel-samd: Fix sporadic "syntax errors"

The GC was deleting memory that was in use because its scan of the
stack missed the very top. Switching to _estack fixes this by relying
on the location from the linker.

Fixes #124

1 files changed, 3 insertions, 1 deletions

diff --git a/py/gc.c b/py/gc.c
index 75fc82382..72eecd7ef 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -104,11 +104,13 @@
 
 #ifdef LOG_HEAP_ACTIVITY
 volatile uint32_t change_me;
-
+#pragma GCC push_options
+#pragma GCC optimize ("O0")
 void __attribute__ ((noinline)) gc_log_change(uint32_t start_block, uint32_t length) {
     change_me += start_block;
     change_me += length; // Break on this line.
 }
+#pragma GCC pop_options
 #endif
 
 // TODO waste less memory; currently requires that all entries in alloc_table have a corresponding block in pool