diff --git a/libs/libc/string/lib_memcmp.c b/libs/libc/string/lib_memcmp.c
index 95b2614a6f..532e9c54ef 100644
--- a/libs/libc/string/lib_memcmp.c
+++ b/libs/libc/string/lib_memcmp.c
@@ -37,8 +37,8 @@
 no_builtin("memcmp")
 int memcmp(FAR const void *s1, FAR const void *s2, size_t n)
 {
-  unsigned char *p1 = (unsigned char *)s1;
-  unsigned char *p2 = (unsigned char *)s2;
+  FAR unsigned char *p1 = (FAR unsigned char *)s1;
+  FAR unsigned char *p2 = (FAR unsigned char *)s2;
 
   while (n-- > 0)
     {
diff --git a/libs/libc/string/lib_memcpy.c b/libs/libc/string/lib_memcpy.c
index d26e6054e3..96c4952635 100644
--- a/libs/libc/string/lib_memcpy.c
+++ b/libs/libc/string/lib_memcpy.c
@@ -43,7 +43,11 @@ FAR void *memcpy(FAR void *dest, FAR const void *src, size_t n)
 {
   FAR unsigned char *pout = (FAR unsigned char *)dest;
   FAR unsigned char *pin  = (FAR unsigned char *)src;
-  while (n-- > 0) *pout++ = *pin++;
+  while (n-- > 0)
+    {
+      *pout++ = *pin++;
+    }
+
   return dest;
 }
 #endif
diff --git a/libs/libc/string/lib_memmem.c b/libs/libc/string/lib_memmem.c
index a9d6c7a773..77dbd4b357 100644
--- a/libs/libc/string/lib_memmem.c
+++ b/libs/libc/string/lib_memmem.c
@@ -42,6 +42,7 @@
  *
  ****************************************************************************/
 
+#undef memmem /* See mm/README.txt */
 FAR void *memmem(FAR const void *haystack, size_t haystacklen,
                  FAR const void *needle, size_t needlelen)
 {
diff --git a/libs/libc/string/lib_mempcpy.c b/libs/libc/string/lib_mempcpy.c
index 605c138c6a..1869800ff3 100644
--- a/libs/libc/string/lib_mempcpy.c
+++ b/libs/libc/string/lib_mempcpy.c
@@ -30,10 +30,6 @@
  * Public Functions
  ****************************************************************************/
 
-/****************************************************************************
- * Name: mempcpy
- ****************************************************************************/
-
 /****************************************************************************
  * Name: mempcpy
  *
@@ -55,6 +51,7 @@
  *
  ****************************************************************************/
 
+#undef mempcpy /* See mm/README.txt */
 FAR void *mempcpy(FAR void *dest, FAR const void *src, size_t n)
 {
   return (FAR char *)memcpy(dest, src, n) + n;
diff --git a/libs/libc/string/lib_memrchr.c b/libs/libc/string/lib_memrchr.c
index a74a9bfe55..6e32e48e00 100644
--- a/libs/libc/string/lib_memrchr.c
+++ b/libs/libc/string/lib_memrchr.c
@@ -44,6 +44,7 @@
  *
  ****************************************************************************/
 
+#undef memrchr /* See mm/README.txt */
 FAR void *memrchr(FAR const void *s, int c, size_t n)
 {
   FAR const unsigned char *p = (FAR const unsigned char *)s + n;
diff --git a/libs/libc/string/lib_skipspace.c b/libs/libc/string/lib_skipspace.c
index 74872c1479..0f025b95f6 100644
--- a/libs/libc/string/lib_skipspace.c
+++ b/libs/libc/string/lib_skipspace.c
@@ -44,9 +44,9 @@
  *
  ****************************************************************************/
 
-void lib_skipspace(const char **pptr)
+void lib_skipspace(FAR const char **pptr)
 {
-  const char *ptr = *pptr;
+  FAR const char *ptr = *pptr;
   while (isspace(*ptr)) ptr++;
   *pptr = ptr;
 }
diff --git a/libs/libc/string/lib_stpcpy.c b/libs/libc/string/lib_stpcpy.c
index 5219c51339..30492aca34 100644
--- a/libs/libc/string/lib_stpcpy.c
+++ b/libs/libc/string/lib_stpcpy.c
@@ -44,6 +44,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_ARCH_STPCPY
+#undef stpcpy /* See mm/README.txt */
 FAR char *stpcpy(FAR char *dest, FAR const char *src)
 {
   while ((*dest++ = *src++) != '\0');
diff --git a/libs/libc/string/lib_stpncpy.c b/libs/libc/string/lib_stpncpy.c
index 4346f5d427..1095c34e65 100644
--- a/libs/libc/string/lib_stpncpy.c
+++ b/libs/libc/string/lib_stpncpy.c
@@ -54,6 +54,7 @@
  ****************************************************************************/
 
 #ifndef CONFIG_LIBC_ARCH_STPNCPY
+#undef stpncpy /* See mm/README.txt */
 FAR char *stpncpy(FAR char *dest, FAR const char *src, size_t n)
 {
   FAR char *end = dest + n; /* End of dest buffer + 1 byte */
diff --git a/libs/libc/string/lib_strcasestr.c b/libs/libc/string/lib_strcasestr.c
index 8da18860a1..369044253d 100644
--- a/libs/libc/string/lib_strcasestr.c
+++ b/libs/libc/string/lib_strcasestr.c
@@ -32,11 +32,12 @@
  * Private Functions
  ****************************************************************************/
 
+#undef strcasechr /* See mm/README.txt */
 static FAR char *strcasechr(FAR const char *s, int uc)
 {
   register char ch;
 
-  for (; *s; s++)
+  for (; *s != '\0'; s++)
     {
       ch = *s;
       if (toupper(ch) == uc)
diff --git a/libs/libc/string/lib_strchr.c b/libs/libc/string/lib_strchr.c
index 3d611c1471..2eab901ef6 100644
--- a/libs/libc/string/lib_strchr.c
+++ b/libs/libc/string/lib_strchr.c
@@ -57,7 +57,7 @@ FAR char *strchr(FAR const char *s, int c)
           return (FAR char *)s;
         }
 
-      if (*s == 0)
+      if (*s == '\0')
         {
           break;
         }
diff --git a/libs/libc/string/lib_strchrnul.c b/libs/libc/string/lib_strchrnul.c
index e6ad6aa59c..04ab71c3d9 100644
--- a/libs/libc/string/lib_strchrnul.c
+++ b/libs/libc/string/lib_strchrnul.c
@@ -47,11 +47,12 @@
  ****************************************************************************/
 
 #if !defined(CONFIG_LIBC_ARCH_STRCHRNUL) && defined(LIBC_BUILD_STRING)
+#undef strchrnul /* See mm/README.txt */
 FAR char *strchrnul(FAR const char *s, int c)
 {
   if (s)
     {
-      while (*s && *s != c)
+      while (*s != '\0' && *s != c)
         {
           s++;
         }
diff --git a/libs/libc/string/lib_strcpy.c b/libs/libc/string/lib_strcpy.c
index a602fab89f..e8fa0cb462 100644
--- a/libs/libc/string/lib_strcpy.c
+++ b/libs/libc/string/lib_strcpy.c
@@ -48,7 +48,7 @@
 #undef strcpy /* See mm/README.txt */
 FAR char *strcpy(FAR char *dest, FAR const char *src)
 {
-  char *tmp = dest;
+  FAR char *tmp = dest;
   while ((*dest++ = *src++) != '\0');
   return tmp;
 }
diff --git a/libs/libc/string/lib_strlcat.c b/libs/libc/string/lib_strlcat.c
index 29365cdd9a..c8e18f9475 100644
--- a/libs/libc/string/lib_strlcat.c
+++ b/libs/libc/string/lib_strlcat.c
@@ -47,6 +47,7 @@
  ****************************************************************************/
 
 #if !defined(CONFIG_LIBC_ARCH_STRLCAT) && defined(LIBC_BUILD_STRING)
+#undef strlcat /* See mm/README.txt */
 size_t strlcat(FAR char *dst, FAR const char *src, size_t dsize)
 {
   FAR const char *odst = dst;
diff --git a/libs/libc/string/lib_strlcpy.c b/libs/libc/string/lib_strlcpy.c
index b108af6cf0..fe70222eae 100644
--- a/libs/libc/string/lib_strlcpy.c
+++ b/libs/libc/string/lib_strlcpy.c
@@ -46,6 +46,7 @@
  ****************************************************************************/
 
 #if !defined(CONFIG_LIBC_ARCH_STRLCPY) && defined(LIBC_BUILD_STRING)
+#undef strlcpy /* See mm/README.txt */
 size_t strlcpy(FAR char *dst, FAR const char *src, size_t dsize)
 {
   FAR const char *osrc = src;
@@ -69,9 +70,9 @@ size_t strlcpy(FAR char *dst, FAR const char *src, size_t dsize)
           *dst = '\0';
         }
 
-      while (*src++);
+      while (*src++ != '\0');
     }
 
-  return (src - osrc - 1);
+  return src - osrc - 1;
 }
 #endif
diff --git a/libs/libc/string/lib_strlen.c b/libs/libc/string/lib_strlen.c
index de180e266f..03cb3a53ed 100644
--- a/libs/libc/string/lib_strlen.c
+++ b/libs/libc/string/lib_strlen.c
@@ -34,9 +34,9 @@
 
 #if !defined(CONFIG_LIBC_ARCH_STRLEN) && defined(LIBC_BUILD_STRING)
 #undef strlen /* See mm/README.txt */
-size_t strlen(const char *s)
+size_t strlen(FAR const char *s)
 {
-  const char *sc;
+  FAR const char *sc;
   for (sc = s; *sc != '\0'; ++sc);
   return sc - s;
 }
diff --git a/libs/libc/string/lib_strncat.c b/libs/libc/string/lib_strncat.c
index 379e503fc1..5e5687a779 100644
--- a/libs/libc/string/lib_strncat.c
+++ b/libs/libc/string/lib_strncat.c
@@ -38,7 +38,7 @@ FAR char *strncat(FAR char *dest, FAR const char *src, size_t n)
 {
   FAR char *ret = dest;
 
-  dest  += strlen(dest);
+  dest += strlen(dest);
   for (; n > 0 && *src != '\0' ; n--)
     {
       *dest++ = *src++;
diff --git a/libs/libc/string/lib_strnlen.c b/libs/libc/string/lib_strnlen.c
index c81fcc6125..e9c5a141a3 100644
--- a/libs/libc/string/lib_strnlen.c
+++ b/libs/libc/string/lib_strnlen.c
@@ -33,9 +33,10 @@
  ****************************************************************************/
 
 #if !defined(CONFIG_LIBC_ARCH_STRNLEN) && defined(LIBC_BUILD_STRING)
-size_t strnlen(const char *s, size_t maxlen)
+#undef strnlen /* See mm/README.txt */
+size_t strnlen(FAR const char *s, size_t maxlen)
 {
-  const char *sc;
+  FAR const char *sc;
   for (sc = s; maxlen != 0 && *sc != '\0'; maxlen--, ++sc);
   return sc - s;
 }
diff --git a/libs/libc/string/lib_strsep.c b/libs/libc/string/lib_strsep.c
index 02cf167304..f40fa5dfb1 100644
--- a/libs/libc/string/lib_strsep.c
+++ b/libs/libc/string/lib_strsep.c
@@ -46,6 +46,7 @@
  *
  ****************************************************************************/
 
+#undef strsep /* See mm/README.txt */
 FAR char *strsep(FAR char **strp, FAR const char *delim)
 {
   FAR char *sbegin = *strp;
diff --git a/libs/libc/string/lib_strstr.c b/libs/libc/string/lib_strstr.c
index 44cbc0456f..d61d14afc4 100644
--- a/libs/libc/string/lib_strstr.c
+++ b/libs/libc/string/lib_strstr.c
@@ -51,6 +51,7 @@
  * string haystack. Returns NULL if needle was not found.
  */
 
+#undef strstr /* See mm/README.txt */
 FAR char *strstr(FAR const char *haystack, FAR const char *needle)
 {
   FAR const unsigned char *needle_cmp_end;
diff --git a/libs/libc/string/lib_strtok.c b/libs/libc/string/lib_strtok.c
index 782294358b..9f3efe79c4 100644
--- a/libs/libc/string/lib_strtok.c
+++ b/libs/libc/string/lib_strtok.c
@@ -28,7 +28,7 @@
  * Private Data
  ****************************************************************************/
 
-static char *g_saveptr = NULL;
+static FAR char *g_saveptr = NULL;
 
 /****************************************************************************
  * Public Functions
@@ -67,7 +67,7 @@ static char *g_saveptr = NULL;
  ****************************************************************************/
 
 #undef strtok /* See mm/README.txt */
-char *strtok(char *str, const char *delim)
+FAR char *strtok(FAR char *str, FAR const char *delim)
 {
   return strtok_r(str, delim, &g_saveptr);
 }
diff --git a/libs/libc/string/lib_strtokr.c b/libs/libc/string/lib_strtokr.c
index f24d3428c2..55487f1588 100644
--- a/libs/libc/string/lib_strtokr.c
+++ b/libs/libc/string/lib_strtokr.c
@@ -75,6 +75,7 @@
  *
  ****************************************************************************/
 
+#undef strtok_r /* See mm/README.txt */
 FAR char *strtok_r(FAR char *str, FAR const char *delim, FAR char **saveptr)
 {
   FAR char *pbegin;
diff --git a/libs/libc/string/lib_strxfrm.c b/libs/libc/string/lib_strxfrm.c
index e19cf80de3..20dd8d481e 100644
--- a/libs/libc/string/lib_strxfrm.c
+++ b/libs/libc/string/lib_strxfrm.c
@@ -69,7 +69,7 @@ size_t strxfrm(FAR char *s1, FAR const char *s2, size_t n)
           return res;
         }
     }
-  while (*s2)
+  while (*s2 != '\0')
     {
       ++s2;
       ++res;