diff --git a/components/libc/compilers/common/cctype.c b/components/libc/compilers/common/cctype.c
index ddcff1b39d8b25b2d302770de5d1ef628ccf77b8..3bfb9fe843c632c6471febeff3ba0ee030383ec9 100644
--- a/components/libc/compilers/common/cctype.c
+++ b/components/libc/compilers/common/cctype.c
@@ -10,12 +10,14 @@
 
 #include "posix/ctype.h"
 
+#if !(defined(__ICCARM__) && (__VER__ > 9000000)) /* IAR9.0 has defined */
 #ifndef isascii /* some toolchain use macro to define it */
 int isascii(int c)
 {
     return c >= 0x00 && c <= 0x7f;
 }
 #endif
+#endif /* !(defined(__ICCARM__) && (__VER__ > 9000000)) */
 
 #ifndef toascii
 int toascii(int c)
diff --git a/components/libc/compilers/common/cstdio.c b/components/libc/compilers/common/cstdio.c
index 3dffe55aa7fc23dc35c7ba94b15b935f9d7c1976..fc14c0b9c3d82a17a11f286502dc4b0cc13ac5ad 100644
--- a/components/libc/compilers/common/cstdio.c
+++ b/components/libc/compilers/common/cstdio.c
@@ -13,6 +13,7 @@
 #include <limits.h>
 #include <sys/errno.h>
 
+#ifdef DFS_USING_POSIX
 ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream)
 {
     char *cur_pos, *new_lineptr;
@@ -83,3 +84,4 @@ ssize_t getline(char **lineptr, size_t *n, FILE *stream)
 {
     return getdelim(lineptr, n, '\n', stream);
 }
+#endif /* DFS_USING_POSIX */
diff --git a/components/libc/compilers/common/include/posix/ctype.h b/components/libc/compilers/common/include/posix/ctype.h
index 0ac42e3faf058741ee2100a2544d1f5159778474..da805af24918e11e171550220ef72035f27b9913 100644
--- a/components/libc/compilers/common/include/posix/ctype.h
+++ b/components/libc/compilers/common/include/posix/ctype.h
@@ -17,9 +17,12 @@ extern "C" {
 
 #include <ctype.h>
 
+#if !(defined(__ICCARM__) && (__VER__ > 9000000)) /* IAR9.0 has defined */
 #ifndef isascii /* some toolchain use macro to define it */
 int isascii(int c);
 #endif
+#endif /* !(defined(__ICCARM__) && (__VER__ > 9000000)) */
+
 #ifndef toascii
 int toascii(int c);
 #endif
diff --git a/components/libc/compilers/common/include/posix/stdio.h b/components/libc/compilers/common/include/posix/stdio.h
index 7dea03bb0d646187df0b4a2b31ca04706b5de1bb..a2cf01f6b6f3db42ac0d1f1168978519a03abc3d 100644
--- a/components/libc/compilers/common/include/posix/stdio.h
+++ b/components/libc/compilers/common/include/posix/stdio.h
@@ -18,8 +18,10 @@ extern "C" {
 #include <stdio.h>
 #include <sys/types.h>
 
+#ifdef DFS_USING_POSIX
 ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream);
 ssize_t getline(char **lineptr, size_t *n, FILE *stream);
+#endif /* DFS_USING_POSIX */
 
 #ifdef __cplusplus
 }