add #undef for some libc function

since it's useful to redirect these functions to others
sometime(e.g. validate the memory before write).

Change-Id: I6253a9231af8809e8362f4bc5a1bd67fb094c3b0

mm/README.txt

@@ -74,6 +74,41 @@ This directory contains the NuttX memory management logic.  This include:
      mm/umm_heap - Holds the user-mode memory allocation interfaces
      mm/kmm_heap - Holds the kernel-mode memory allocation interfaces
 
+   Debugging:
+
+    Please follow these steps to hook all memory related routines:
+
+    1.Add a new header file(e.g. xxx_malloc.h):
+
+      ...
+      #include <malloc.h>
+      #include <stdlib.h>
+      #include <string.h>
+      #include <strings.h>
+
+      #ifndef __ASSEMBLY__
+      FAR void *xxx_malloc(FAR const char *file, int line, size_t size);
+      void xxx_free(FAR const char *file, int line, FAR const void *ptr);
+      FAR void *xxx_memcpy(FAR const char *file, int line,
+                           FAR void *dst, FAR const void *src, size_t len);
+      ...
+      #define malloc(s) xxx_malloc(__FILE__, __LINE__, s)
+      #define free(p) xxx_free(__FILE__, __LINE__, p)
+      #define memcpy(d, s, l) xxx_memcpy(__FILE__, __LINE__, d, s, l)
+      ...
+      #endif
+      ...
+
+    2.Implement xxx_malloc, xxx_free, xxx_memcpy... in source code, you can:
+      a.Modify some arguments(e.g. extend the allocation size for redzone)
+      d.Check the critical arguments(e.g. pointer and length) in the range 
+      b.Forward to the original implementation(call malloc/free/memcpy)
+      c.Attach the context info(e.g. file and line) before return
+
+    3.Enable the hook by either:
+      a.Include xxx_malloc.h in your source code to hook one file
+      b.Add -include xxx_malloc.h to CFLAGS to hook all source code
+
 2) Granule Allocator.
 
      A non-standard granule allocator is also available in this directory  The

mm/umm_heap/umm_calloc.c

@@ -42,6 +42,7 @@
  *
  ****************************************************************************/
 
+#undef calloc /* See mm/README.txt */
 FAR void *calloc(size_t n, size_t elem_size)
 {
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)

mm/umm_heap/umm_free.c

@@ -43,6 +43,7 @@
  *
  ****************************************************************************/
 
+#undef free /* See mm/README.txt */
 void free(FAR void *mem)
 {
   mm_free(USR_HEAP, mem);

mm/umm_heap/umm_malloc.c

@@ -49,6 +49,7 @@
  *
  ****************************************************************************/
 
+#undef malloc /* See mm/README.txt */
 FAR void *malloc(size_t size)
 {
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)

mm/umm_heap/umm_malloc_size.c

@@ -32,6 +32,7 @@
  * Public Functions
  ****************************************************************************/
 
+#undef malloc_size /* See mm/README.txt */
 size_t malloc_size(FAR void *mem)
 {
   return mm_malloc_size(mem);

mm/umm_heap/umm_memalign.c

@@ -48,6 +48,7 @@
  *
  ****************************************************************************/
 
+#undef memalign /* See mm/README.txt */
 FAR void *memalign(size_t alignment, size_t size)
 {
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)

mm/umm_heap/umm_realloc.c

@@ -50,6 +50,7 @@
  *
  ****************************************************************************/
 
+#undef realloc /* See mm/README.txt */
 FAR void *realloc(FAR void *oldmem, size_t size)
 {
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)

mm/umm_heap/umm_zalloc.c

@@ -49,6 +49,7 @@
  *
  ****************************************************************************/
 
+#undef zalloc /* See mm/README.txt */
 FAR void *zalloc(size_t size)
 {
 #ifdef CONFIG_ARCH_ADDRENV