Revert "解决将RT_NULL当做数字0使用的问题"

This reverts commit 6a05ddf63d.

components/finsh/msh_file.c

@@ -608,7 +608,7 @@ MSH_CMD_EXPORT_ALIAS(cmd_echo, echo, echo string to file);
 static int cmd_tail(int argc, char **argv)
 {
     int fd;
-    char c = '\0';
+    char c = RT_NULL;
     char *file_name = RT_NULL;
     rt_uint32_t total_lines = 0;
     rt_uint32_t target_line = 0;

components/libc/compilers/common/ctime.c

@@ -180,7 +180,7 @@ struct tm *gmtime_r(const time_t *timep, struct tm *r)
         return RT_NULL;
     }
 
-    rt_memset(r, 0, sizeof(struct tm));
+    rt_memset(r, RT_NULL, sizeof(struct tm));
 
     r->tm_sec = work % 60;
     work /= 60;
@@ -258,7 +258,7 @@ char* asctime_r(const struct tm *t, char *buf)
         return RT_NULL;
     }
 
-    rt_memset(buf, 0, 26);
+    rt_memset(buf, RT_NULL, 26);
 
     /* Checking input validity */
     if ((int)rt_strlen(days) <= (t->tm_wday << 2) || (int)rt_strlen(months) <= (t->tm_mon << 2))

components/libc/posix/pthreads/pthread.c

@@ -136,7 +136,7 @@ void _pthread_data_destroy(_pthread_data_t *ptd)
         ptd->magic = 0x0;
 
         /* clear the "ptd->tid->user_data" */
-        ptd->tid->user_data = 0;
+        ptd->tid->user_data = RT_NULL;
 
         /* free ptd */
         rt_free(ptd);

include/rtdef.h

@@ -123,11 +123,7 @@ typedef rt_base_t                       rt_off_t;       /**< Type for offset */
 #define RT_FALSE                        0               /**< boolean fails */
 
 /* null pointer definition */
-#ifdef RT_USING_LIBC
-#define RT_NULL                         NULL            /**< null pointer */
-#else
-#define RT_NULL                         (0)             /**< null pointer */
-#endif /* RT_USING_LIBC */
+#define RT_NULL                         0
 
 /**@}*/