From dd147925e52aa205a09d631984c545f9c99c52c2 Mon Sep 17 00:00:00 2001
From: Meco Man <920369182@qq.com>
Date: Thu, 11 Feb 2021 13:41:24 +0800
Subject: [PATCH] fix time() return value

---
 components/libc/compilers/common/time.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/components/libc/compilers/common/time.c b/components/libc/compilers/common/time.c
index e1c9340e6..fecae28f9 100644
--- a/components/libc/compilers/common/time.c
+++ b/components/libc/compilers/common/time.c
@@ -174,23 +174,24 @@ double difftime (time_t tim1, time_t tim2)
  *
  * @param time_t * t the timestamp pointer, if not used, keep NULL.
  *
- * @return time_t return timestamp current.
+ * @return The value ((time_t)-1) is returned if the calendar time is not available. 
+ *         If timer is not a NULL pointer, the return value is also stored in timer.
  *
  */
 RT_WEAK time_t time(time_t *t)
 {
-    time_t time_now = 0;
+    time_t time_now = ((time_t)-1); /* default is not available */
 
 #ifdef RT_USING_RTC
     static rt_device_t device = RT_NULL;
 
-    /* optimization: find rtc device only first. */
+    /* optimization: find rtc device only first */
     if (device == RT_NULL)
     {
         device = rt_device_find("rtc");
     }
 
-    /* read timestamp from RTC device. */
+    /* read timestamp from RTC device */
     if (device != RT_NULL)
     {
         if (rt_device_open(device, 0) == RT_EOK)
-- 
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