diff --git a/include/os/osString.h b/include/os/osString.h
index 4982ac8bfd..8e8f1546e7 100644
--- a/include/os/osString.h
+++ b/include/os/osString.h
@@ -47,18 +47,13 @@ typedef int32_t TdUcs4;
 #define strtof      STR_TO_F_FUNC_TAOS_FORBID
 #endif
 
-#ifdef WINDOWS
-#define tstrdup(str) _strdup(str)
-#else
-#define tstrdup(str) strdup(str)
-#endif
-
 #define tstrncpy(dst, src, size)   \
   do {                             \
     strncpy((dst), (src), (size)); \
     (dst)[(size)-1] = 0;           \
   } while (0)
 
+char   *tstrdup(const char *src);
 int32_t taosUcs4len(TdUcs4 *ucs4);
 int64_t taosStr2int64(const char *str);
 
diff --git a/source/os/src/osString.c b/source/os/src/osString.c
index 8aac606473..9119c1d470 100644
--- a/source/os/src/osString.c
+++ b/source/os/src/osString.c
@@ -24,6 +24,14 @@
 extern int wcwidth(wchar_t c);
 extern int wcswidth(const wchar_t *s, size_t n);
 
+char *tstrdup(const char *str) {
+#ifdef WINDOWS
+  return _strdup(str);
+#else
+  return strdup(str);
+#endif
+}
+
 #ifdef WINDOWS
 char *strsep(char **stringp, const char *delim) {
   char       *s;