libc: minimal: implement time() API

lib/libc/minimal/CMakeLists.txt

@@ -20,3 +20,5 @@ zephyr_library_sources(
   source/stdout/fprintf.c
   source/time/gmtime.c
 )
+
+zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK source/time/time.c)

lib/libc/minimal/include/time.h

@@ -52,6 +52,8 @@ struct tm *gmtime(const time_t *timep);
 struct tm *gmtime_r(const time_t *_MLIBC_RESTRICT timep,
 		    struct tm *_MLIBC_RESTRICT result);
 
+time_t time(time_t *tloc);
+
 #ifdef __cplusplus
 }
 #endif

lib/libc/minimal/source/time/time.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2021 Golioth, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <time.h>
+
+/* clock_gettime() prototype */
+#include <posix/time.h>
+
+time_t time(time_t *tloc)
+{
+	struct timespec ts;
+	int ret;
+
+	ret = clock_gettime(CLOCK_REALTIME, &ts);
+	if (ret < 0) {
+		/* errno is already set by clock_gettime */
+		return (time_t) -1;
+	}
+
+	if (tloc) {
+		*tloc = ts.tv_sec;
+	}
+
+	return ts.tv_sec;
+}

samples/net/civetweb/common/src/libc_extensions.c

@@ -159,11 +159,6 @@ long long strtoll(const char *str, char **endptr, int base)
 	return (long long)strtol(str, endptr, base);
 }
 
-time_t time(time_t *t)
-{
-	return 0;
-}
-
 /*
  * Most of the wrappers below are copies of the wrappers in net/sockets.h,
  * but they are available only if CONFIG_NET_SOCKETS_POSIX_NAMES is enabled