samd: Add support for building with user C modules.

Fixes issue #7545.

Signed-off-by: Damien George <damien@micropython.org>

ports/samd/Makefile

@@ -33,7 +33,11 @@ CFLAGS_MCU_SAMD21 = -mtune=cortex-m0plus -mcpu=cortex-m0plus -msoft-float
 CFLAGS_MCU_SAMD51 = -mtune=cortex-m4 -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard
 CFLAGS = $(INC) -Wall -Werror -std=c99 -nostdlib -mthumb $(CFLAGS_MCU_$(MCU_SERIES)) -fsingle-precision-constant -Wdouble-promotion
 CFLAGS += -DMCU_$(MCU_SERIES) -D__$(CMSIS_MCU)__
+CFLAGS += $(CFLAGS_MOD)
+
 LDFLAGS = -nostdlib $(addprefix -T,$(LD_FILES)) -Map=$@.map --cref
+LDFLAGS += $(LDFLAGS_MOD)
+
 LIBS = $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
 
 # Tune for Debugging or Optimization
@@ -45,6 +49,14 @@ LDFLAGS += --gc-sections
 CFLAGS += -fdata-sections -ffunction-sections
 endif
 
+# Flags for optional C++ source code
+CXXFLAGS += $(filter-out -std=c99,$(CFLAGS))
+CXXFLAGS += $(CXXFLAGS_MOD)
+ifneq ($(SRC_CXX)$(SRC_MOD_CXX),)
+LIBSTDCPP_FILE_NAME = "$(shell $(CXX) $(CXXFLAGS) -print-file-name=libstdc++.a)"
+LDFLAGS += -L"$(shell dirname $(LIBSTDCPP_FILE_NAME))"
+endif
+
 SRC_C = \
 	main.c \
 	modutime.c \
@@ -70,6 +82,10 @@ SRC_C = \
 	shared/runtime/pyexec.c \
 	shared/runtime/stdout_helpers.c \
 
+SRC_C += $(SRC_MOD)
+
+SRC_CXX += $(SRC_MOD_CXX)
+
 ifeq ($(MCU_SERIES),SAMD21)
 SRC_S = shared/runtime/gchelper_m0.s
 else
@@ -77,10 +93,11 @@ SRC_S = shared/runtime/gchelper_m3.s
 endif
 
 # List of sources for qstr extraction
-SRC_QSTR += modutime.c modmachine.c
+SRC_QSTR += modutime.c modmachine.c $(SRC_MOD) $(SRC_CXX)
 
 OBJ += $(PY_O)
 OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_CXX:.cpp=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_S:.s=.o))
 
 # Workaround for bug in older gcc, warning on "static usbd_device_t _usbd_dev = { 0 };"

ports/samd/main.c

@@ -87,6 +87,11 @@ void nlr_jump_fail(void *val) {
     }
 }
 
+void abort(void) {
+    for (;;) {
+    }
+}
+
 #ifndef NDEBUG
 void MP_WEAK __assert_func(const char *file, int line, const char *func, const char *expr) {
     mp_printf(MP_PYTHON_PRINTER, "Assertion '%s' failed, at file %s:%d\n", expr, file, line);

ports/samd/sections.ld

@@ -11,10 +11,20 @@ SECTIONS
         *(.rodata*)
         . = ALIGN(4);
         _etext = .;
-        _sidata = _etext;
     } >FLASH
 
-    .data : AT ( _sidata )
+    /* For C++ exception handling */
+    .ARM :
+    {
+        __exidx_start = .;
+        *(.ARM.exidx*)
+        __exidx_end = .;
+    } >FLASH
+
+    /* Used by the start-up code to initialise data */
+    _sidata = LOADADDR(.data);
+
+    .data :
     {
         . = ALIGN(4);
         _sdata = .;
@@ -22,7 +32,7 @@ SECTIONS
         *(.data*)
         . = ALIGN(4);
         _edata = .;
-    } >RAM
+    } >RAM AT> FLASH
 
     .bss :
     {