diff --git a/inc/core/MicroBitHeapAllocator.h b/inc/core/MicroBitHeapAllocator.h
index 10aa5c94..115a2511 100644
--- a/inc/core/MicroBitHeapAllocator.h
+++ b/inc/core/MicroBitHeapAllocator.h
@@ -52,6 +52,7 @@ DEALINGS IN THE SOFTWARE.
 #define MICROBIT_HEAP_ALLOCTOR_H
 
 #include "MicroBitConfig.h"
+#include <new>
 
 // The maximum number of heap segments that can be created.
 #define MICROBIT_MAXIMUM_HEAPS          2
@@ -85,4 +86,27 @@ struct HeapDefinition
 int microbit_create_heap(uint32_t start, uint32_t end);
 void microbit_heap_print();
 
+/**
+  * Attempt to allocate a given amount of memory from any of our configured heap areas.
+  *
+  * @param size The amount of memory, in bytes, to allocate.
+  *
+  * @return A pointer to the allocated memory, or NULL if insufficient memory is available.
+  */
+void *_microbit_malloc(size_t size);
+void* _microbit_calloc (size_t num, size_t size);
+void* _microbit_realloc (void* ptr, size_t size);
+
+/**
+  * Release a given area of memory from the heap.
+  *
+  * @param mem The memory area to release.
+  */
+void _microbit_free(void *mem);
+
+#define malloc _microbit_malloc
+#define free _microbit_free
+#define calloc _microbit_calloc
+#define realloc _microbit_realloc
+
 #endif
diff --git a/inc/core/MicroBitUtil.h b/inc/core/MicroBitUtil.h
index d9fc5f74..087cf8d4 100644
--- a/inc/core/MicroBitUtil.h
+++ b/inc/core/MicroBitUtil.h
@@ -32,7 +32,7 @@ DEALINGS IN THE SOFTWARE.
 
 #include "MicroBitConfig.h"
 
-#define CREATE_KEY_VALUE_TABLE(NAME, PAIRS) const KeyValueTable NAME { PAIRS, sizeof(PAIRS) / sizeof(KeyValueTableEntry) };
+#define CREATE_KEY_VALUE_TABLE(NAME, PAIRS) const KeyValueTable NAME = { PAIRS, sizeof(PAIRS) / sizeof(KeyValueTableEntry) };
 
 /**
  * Provides a simple key/value pair lookup table with range lookup support.
diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index f98a2ec9..0932efb1 100755
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -86,17 +86,15 @@ if (YOTTA_CFG_MICROBIT_CONFIGFILE)
 endif ()
 
 if(CMAKE_COMPILER_IS_GNUCC)
-  file(REMOVE "asm/CortexContextSwitch.s")
-  configure_file("asm/CortexContextSwitch.s.gcc" "asm/CortexContextSwitch.s" COPYONLY)
+  set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
+    "asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s"
+  )
 else()
-  file(REMOVE "asm/CortexContextSwitch.s")
-  configure_file("asm/CortexContextSwitch.s.armcc" "asm/CortexContextSwitch.s" COPYONLY)
+  set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
+    "asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S"
+  )
 endif()
 
-set(YOTTA_AUTO_MICROBIT-DAL_S_FILES
-    "asm/CortexContextSwitch.s"
-)
-
 add_library(microbit-dal
     ${YOTTA_AUTO_MICROBIT-DAL_CPP_FILES}
     ${YOTTA_AUTO_MICROBIT-DAL_S_FILES}
diff --git a/source/asm/CortexContextSwitch.s.armcc b/source/asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S
similarity index 100%
rename from source/asm/CortexContextSwitch.s.armcc
rename to source/asm/TOOLCHAIN_ARM_STD/CortexContextSwitch.S
diff --git a/source/asm/CortexContextSwitch.s.gcc b/source/asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s
similarity index 100%
rename from source/asm/CortexContextSwitch.s.gcc
rename to source/asm/TOOLCHAIN_GCC_ARM/CortexContextSwitch.s
diff --git a/source/core/MicroBitHeapAllocator.cpp b/source/core/MicroBitHeapAllocator.cpp
index c42b3daa..0fd0c6c1 100644
--- a/source/core/MicroBitHeapAllocator.cpp
+++ b/source/core/MicroBitHeapAllocator.cpp
@@ -59,7 +59,13 @@ DEALINGS IN THE SOFTWARE.
 // A list of all active heap regions, and their dimensions in memory.
 HeapDefinition heap[MICROBIT_MAXIMUM_HEAPS] = { };
 uint8_t heap_count = 0;
-extern "C" int __end__;
+#if defined __CC_ARM || defined __ARMCC_VERSION
+#define HEAP_START Image$$RW_IRAM1$$ZI$$Limit
+#else
+#define HEAP_START __end__
+#endif
+
+extern "C" int HEAP_START;
 
 #if CONFIG_ENABLED(MICROBIT_DBG) && CONFIG_ENABLED(MICROBIT_HEAP_DBG)
 // Diplays a usage summary about a given heap...
@@ -271,7 +277,7 @@ void *microbit_malloc(size_t size, HeapDefinition &heap)
   *
   * @return A pointer to the allocated memory, or NULL if insufficient memory is available.
   */
-void *malloc(size_t size)
+void *_microbit_malloc(size_t size)
 {
     static uint8_t initialised = 0;
     void *p;
@@ -280,7 +286,7 @@ void *malloc(size_t size)
     {
         heap_count = 0;
 
-        if(microbit_create_heap((uint32_t)(&__end__), (uint32_t)(MICROBIT_HEAP_END)) == MICROBIT_INVALID_PARAMETER)
+        if(microbit_create_heap((uint32_t)(&HEAP_START), (uint32_t)(MICROBIT_HEAP_END)) == MICROBIT_INVALID_PARAMETER)
             microbit_panic(MICROBIT_HEAP_ERROR);
 
         initialised = 1;
@@ -319,7 +325,7 @@ void *malloc(size_t size)
   *
   * @param mem The memory area to release.
   */
-void free(void *mem)
+void _microbit_free(void *mem)
 {
 	uint32_t	*memory = (uint32_t *)mem;
 	uint32_t	*cb = memory-1;
@@ -351,7 +357,7 @@ void free(void *mem)
     microbit_panic(MICROBIT_HEAP_ERROR);
 }
 
-void* calloc (size_t num, size_t size)
+void* _microbit_calloc (size_t num, size_t size)
 {
     void *mem = malloc(num*size);
 
@@ -361,7 +367,7 @@ void* calloc (size_t num, size_t size)
     return mem;
 }
 
-void* realloc (void* ptr, size_t size)
+void* _microbit_realloc (void* ptr, size_t size)
 {
     void *mem = malloc(size);
 
diff --git a/source/drivers/MicroBitCompassCalibrator.cpp b/source/drivers/MicroBitCompassCalibrator.cpp
index 09f5f1b5..470c726f 100644
--- a/source/drivers/MicroBitCompassCalibrator.cpp
+++ b/source/drivers/MicroBitCompassCalibrator.cpp
@@ -226,8 +226,8 @@ CompassCalibration MicroBitCompassCalibrator::spherify(Sample3D centre, Sample3D
 Sample3D MicroBitCompassCalibrator::approximateCentre(Sample3D *data, int samples)
 {
     Sample3D c,t;
-    Sample3D centre = { 0,0,0 };
-    Sample3D best = { 0,0,0 };
+    Sample3D centre;
+    Sample3D best;
 
     float score;