fix(rtthread): implement lv_strcat function in rt-thread due to absence of rt_strcat (lvgl#5920)

Signed-off-by: lhdjply <[email protected]>

Author: lhdjply

src/stdlib/builtin/lv_string_builtin.c

@@ -229,12 +229,8 @@ char * lv_strdup(const char * src)
 
 char * lv_strcat(char * dst, const char * src)
 {
-    char * tmp = dst;
-    while(*dst != '\0') {
-        dst++;
-    }
-    lv_strcpy(dst, src);
-    return tmp;
+    lv_strcpy(dst + lv_strlen(dst), src);
+    return dst;
 }
 
 char * lv_strncat(char * dst, const char * src, size_t src_len)

src/stdlib/rtthread/lv_string_rtthread.c

@@ -87,7 +87,10 @@ char * lv_strdup(const char * src)
 
 char * lv_strcat(char * dst, const char * src)
 {
-    return strcat(dst, src);
+    /*Since RT-thread does not have rt_strcat,
+    the following code is used instead.*/
+    lv_strcpy(dst + lv_strlen(dst), src);
+    return dst;
 }
 
 char * lv_strncat(char * dst, const char * src, size_t src_len)