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

libs/libc/string/lib_index.c

@@ -32,6 +32,7 @@
  * Name: index
  ****************************************************************************/
 
+#undef index /* See mm/README.txt */
 FAR char *index(FAR const char *s, int c)
 {
   return strchr(s, c);

libs/libc/string/lib_memccpy.c

@@ -46,6 +46,7 @@
  *
  ****************************************************************************/
 
+#undef memccpy /* See mm/README.txt */
 FAR void *memccpy(FAR void *s1, FAR const void *s2, int c, size_t n)
 {
   FAR unsigned char *pout = (FAR unsigned char *)s1;

libs/libc/string/lib_memchr.c

@@ -44,6 +44,7 @@
  *
  ****************************************************************************/
 
+#undef memchr /* See mm/README.txt */
 FAR void *memchr(FAR const void *s, int c, size_t n)
 {
   FAR const unsigned char *p = (FAR const unsigned char *)s;

libs/libc/string/lib_memcmp.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_MEMCMP
+#undef memcmp /* See mm/README.txt */
 int memcmp(FAR const void *s1, FAR const void *s2, size_t n)
 {
   unsigned char *p1 = (unsigned char *)s1;

libs/libc/string/lib_memcpy.c

@@ -35,6 +35,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_MEMCPY
+#undef memcpy /* See mm/README.txt */
 FAR void *memcpy(FAR void *dest, FAR const void *src, size_t n)
 {
   FAR unsigned char *pout = (FAR unsigned char *)dest;

libs/libc/string/lib_memmove.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_MEMMOVE
+#undef memmove /* See mm/README.txt */
 FAR void *memmove(FAR void *dest, FAR const void *src, size_t count)
 {
   FAR char *tmp;

libs/libc/string/lib_memset.c

@@ -47,6 +47,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_MEMSET
+#undef memset /* See mm/README.txt */
 FAR void *memset(FAR void *s, int c, size_t n)
 {
 #ifdef CONFIG_MEMSET_OPTSPEED

libs/libc/string/lib_rindex.c

@@ -32,6 +32,7 @@
  * Name: rindex
  ****************************************************************************/
 
+#undef rindex /* See mm/README.txt */
 FAR char *rindex(FAR const char *s, int c)
 {
   return strrchr(s, c);

libs/libc/string/lib_strcasecmp.c

@@ -32,6 +32,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STRCASECMP
+#undef strcasecmp /* See mm/README.txt */
 int strcasecmp(FAR const char *cs, FAR const char *ct)
 {
   int result;

libs/libc/string/lib_strcat.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STRCAT
+#undef strcat /* See mm/README.txt */
 char *strcat(char *dest, const char *src)
 {
   char *ret   = dest;

libs/libc/string/lib_strchr.c

@@ -45,6 +45,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STRCHR
+#undef strchr /* See mm/README.txt */
 FAR char *strchr(FAR const char *s, int c)
 {
   if (s)

libs/libc/string/lib_strcmp.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STRCMP
+#undef strcmp /* See mm/README.txt */
 int strcmp(FAR const char *cs, FAR const char *ct)
 {
   register signed char result;

libs/libc/string/lib_strcpy.c

@@ -43,6 +43,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STRCPY
+#undef strcpy /* See mm/README.txt */
 FAR char *strcpy(FAR char *dest, FAR const char *src)
 {
   char *tmp = dest;

libs/libc/string/lib_strcspn.c

@@ -39,6 +39,7 @@
  *
  ****************************************************************************/
 
+#undef strcspn /* See mm/README.txt */
 size_t strcspn(const char *s, const char *reject)
 {
   size_t i;

libs/libc/string/lib_strdup.c

@@ -32,6 +32,7 @@
  * Public Functions
  ****************************************************************************/
 
+#undef strdup /* See mm/README.txt */
 FAR char *strdup(FAR const char *s)
 {
   FAR char *news = NULL;

libs/libc/string/lib_strlen.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STRLEN
+#undef strlen /* See mm/README.txt */
 size_t strlen(const char *s)
 {
   const char *sc;

libs/libc/string/lib_strncasecmp.c

@@ -33,6 +33,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STRNCASECMP
+#undef strncasecmp /* See mm/README.txt */
 int strncasecmp(const char *cs, const char *ct, size_t nb)
 {
   int result = 0;

libs/libc/string/lib_strncat.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STRNCAT
+#undef strncat /* See mm/README.txt */
 char *strncat(char *dest, const char *src, size_t n)
 {
   char *ret   = dest;

libs/libc/string/lib_strncmp.c

@@ -31,6 +31,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STRNCMP
+#undef strncmp /* See mm/README.txt */
 int strncmp(const char *cs, const char *ct, size_t nb)
 {
   int result = 0;

libs/libc/string/lib_strncpy.c

@@ -52,6 +52,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STRNCPY
+#undef strncpy /* See mm/README.txt */
 FAR char *strncpy(FAR char *dest, FAR const char *src, size_t n)
 {
   FAR char *ret = dest;     /* Value to be returned */

libs/libc/string/lib_strndup.c

@@ -49,6 +49,7 @@
  *
  ****************************************************************************/
 
+#undef strndup /* See mm/README.txt */
 FAR char *strndup(FAR const char *s, size_t size)
 {
   FAR char *news = NULL;

libs/libc/string/lib_strpbrk.c

@@ -30,6 +30,7 @@
  * Public Functions
  ****************************************************************************/
 
+#undef strpbrk /* See mm/README.txt */
 FAR char *strpbrk(FAR const char *str, FAR const char *charset)
 {
   /* Sanity checking */

libs/libc/string/lib_strrchr.c

@@ -34,6 +34,7 @@
  * occurrence of the character c in the string s.
  */
 
+#undef strrchr /* See mm/README.txt */
 FAR char *strrchr(FAR const char *s, int c)
 {
   if (s)

libs/libc/string/lib_strspn.c

@@ -39,6 +39,7 @@
  *
  ****************************************************************************/
 
+#undef strspn /* See mm/README.txt */
 size_t strspn(const char *s, const char *accept)
 {
   size_t i;

libs/libc/string/lib_strstr.c

@@ -30,6 +30,7 @@
  * Public Functions
  ****************************************************************************/
 
+#undef strstr /* See mm/README.txt */
 FAR char *strstr(FAR const char *str, FAR const char *substr)
 {
   FAR const char *candidate; /* Candidate in str with matching start character */

libs/libc/string/lib_strtok.c

@@ -66,6 +66,7 @@ static char *g_saveptr = NULL;
  *
  ****************************************************************************/
 
+#undef strtok /* See mm/README.txt */
 char *strtok(char *str, const char *delim)
 {
   return strtok_r(str, delim, &g_saveptr);