Add external memory allocation functions

teensy4/extmem.c

+// External memory allocation functions.  Attempt to use external memory,
+// but automatically fall back to internal RAM if external RAM can't be used.
+
+#include <stdlib.h>
+#include "smalloc.h"
+#include "wiring.h"
+
+#if defined(ARDUINO_TEENSY41)
+// Teensy 4.1 external RAM address range is 0x70000000 to 0x7FFFFFFF
+#define HAS_EXTRAM
+#define IS_EXTMEM(addr) (((uint32_t)ptr >> 28) == 7)
+#endif
+
+
+void *extmem_malloc(size_t size)
+{
+#ifdef HAS_EXTRAM
+	void *ptr = sm_malloc_pool(&extmem_smalloc_pool, size);
+	if (ptr) return ptr;
+#endif
+	return malloc(size);
+}
+
+void extmem_free(void *ptr)
+{
+#ifdef HAS_EXTRAM
+	if (IS_EXTMEM(ptr)) {
+		sm_free_pool(&extmem_smalloc_pool, ptr);
+		return;
+	}
+#endif
+	free(ptr);
+}
+
+void *extmem_calloc(size_t nmemb, size_t size)
+{
+	return extmem_malloc(nmemb * size);
+}
+
+void *extmem_realloc(void *ptr, size_t size)
+{
+#ifdef HAS_EXTRAM
+	if (IS_EXTMEM(ptr)) {
+		return sm_realloc_pool(&extmem_smalloc_pool, ptr, size);
+	}
+#endif
+	return realloc(ptr, size);
+}
+
+

teensy4/startup.c

 #include "usb_dev.h"
 #include "avr/pgmspace.h"
 #include "smalloc.h"
+#include <string.h>
 
 #include "debug/printf.h"
 

teensy4/wiring.h

 void setup(void);
 void loop(void);
 
+void *extmem_malloc(size_t size);
+void extmem_free(void *ptr);
+void *extmem_calloc(size_t nmemb, size_t size);
+void *extmem_realloc(void *ptr, size_t size);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif