Merge pull request adafruit#1772 from tannewt/fix_gc_never_free

Check that a never free pointer is on the heap.

Author: dhalbert

ports/atmel-samd/boards/itsybitsy_m0_express/mpconfigboard.h

@@ -36,3 +36,7 @@
 // USB is always used internally so skip the pin objects for it.
 #define IGNORE_PIN_PA24     1
 #define IGNORE_PIN_PA25     1
+
+// Not connected
+#define IGNORE_PIN_PA13     1
+#define IGNORE_PIN_PA28     1

ports/atmel-samd/boards/sparkfun_lumidrive/mpconfigboard.mk

@@ -11,7 +11,7 @@ CHIP_VARIANT = SAMD21G18A
 CHIP_FAMILY = samd21
 
 # Make room for frozen libraries.
-CFLAGS_INLINE_LIMIT = 65
+CFLAGS_INLINE_LIMIT = 55
 
 EXTERNAL_FLASH_DEVICE_COUNT = 1
 EXTERNAL_FLASH_DEVICES = "W25Q32FV"

py/gc.c

@@ -945,6 +945,10 @@ void *gc_realloc(void *ptr_in, size_t n_bytes, bool allow_move) {
 #endif // Alternative gc_realloc impl
 
 bool gc_never_free(void *ptr) {
+    // Check to make sure the pointer is on the heap in the first place.
+    if (gc_nbytes(ptr) == 0) {
+        return false;
+    }
     // Pointers are stored in a linked list where each block is BYTES_PER_BLOCK long and the first
     // pointer is the next block of pointers.
     void ** current_reference_block = MP_STATE_MEM(permanent_pointers);