stm32: Add configuration to build in nanbox mode.

Most stm32 boards can now be built in nan-boxing mode via:

    $ make NANBOX=1

Note that if float is enabled then it will be forced to double-precision.
Also, native emitters will be disabled.

ports/stm32/Makefile

@@ -95,6 +95,15 @@ CFLAGS += -I$(BOARD_DIR)
 CFLAGS += -DSTM32_HAL_H='<stm32$(MCU_SERIES)xx_hal.h>'
 CFLAGS += -DMICROPY_HW_VTOR=$(TEXT0_ADDR)
 
+# Configure for nan-boxing object model if requested
+ifeq ($(NANBOX),1)
+CFLAGS += -DMP_CONFIGFILE='"mpconfigport_nanbox.h"'
+ifneq ($(MICROPY_FLOAT_IMPL),none)
+MICROPY_FLOAT_IMPL = double
+endif
+endif
+
+# Configure floating point support
 ifeq ($(MICROPY_FLOAT_IMPL),double)
 CFLAGS += -DMICROPY_FLOAT_IMPL=MICROPY_FLOAT_IMPL_DOUBLE
 else

ports/stm32/mpconfigport.h

@@ -305,11 +305,14 @@ struct _mp_bluetooth_nimble_root_pointers_t;
 
 #define MP_SSIZE_MAX (0x7fffffff)
 
+// Assume that if we already defined the obj repr then we also defined these items
+#ifndef MICROPY_OBJ_REPR
 #define UINT_FMT "%u"
 #define INT_FMT "%d"
-
 typedef int mp_int_t; // must be pointer size
 typedef unsigned int mp_uint_t; // must be pointer size
+#endif
+
 typedef long mp_off_t;
 
 #define MP_PLAT_PRINT_STRN(str, len) mp_hal_stdout_tx_strn_cooked(str, len)

ports/stm32/mpconfigport_nanbox.h

@@ -0,0 +1,43 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdint.h>
+
+// Select nan-boxing object model
+#define MICROPY_OBJ_REPR (MICROPY_OBJ_REPR_D)
+
+// Native emitters don't work with nan-boxing
+#define MICROPY_EMIT_THUMB (0)
+#define MICROPY_EMIT_INLINE_THUMB (0)
+
+// Types needed for nan-boxing
+#define UINT_FMT "%llu"
+#define INT_FMT "%lld"
+typedef int64_t mp_int_t;
+typedef uint64_t mp_uint_t;
+
+// Include base configuration file for rest of configuration
+#include <mpconfigport.h>