Merge pull request adafruit#1080 from jepler/uart-ll

 UART: Always allocate UART objects in the long-lived pool

Author: tannewt

ports/atmel-samd/common-hal/busio/UART.c

@@ -132,7 +132,13 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 
     if (rx && receiver_buffer_size > 0) {
         self->buffer_length = receiver_buffer_size;
-        self->buffer = (uint8_t *) gc_alloc(self->buffer_length * sizeof(uint8_t), false, false);
+        // Initially allocate the UART's buffer in the long-lived part of the
+        // heap.  UARTs are generally long-lived objects, but the "make long-
+        // lived" machinery is incapable of moving internal pointers like
+        // self->buffer, so do it manually.  (However, as long as internal
+        // pointers like this are NOT moved, allocating the buffer
+        // in the long-lived pool is not strictly necessary)
+        self->buffer = (uint8_t *) gc_alloc(self->buffer_length * sizeof(uint8_t), false, true);
         if (self->buffer == NULL) {
             common_hal_busio_uart_deinit(self);
             mp_raise_msg(&mp_type_MemoryError, "Failed to allocate RX buffer");

shared-bindings/busio/UART.c

@@ -66,7 +66,11 @@ extern const busio_uart_parity_obj_t busio_uart_parity_odd_obj;
 
 STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *pos_args) {
     mp_arg_check_num(n_args, n_kw, 0, MP_OBJ_FUN_ARGS_MAX, true);
-    busio_uart_obj_t *self = m_new_obj(busio_uart_obj_t);
+    // Always initially allocate the UART object within the long-lived heap.
+    // This is needed to avoid crashes with certain UART implementations which
+    // cannot accomodate being moved after creation. (See
+    // https://github.com/adafruit/circuitpython/issues/1056)
+    busio_uart_obj_t *self = m_new_ll_obj(busio_uart_obj_t);
     self->base.type = &busio_uart_type;
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, pos_args + n_args);