This is used in various selftests and will be handy when integrating
those with nolibc.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
---
 tools/include/nolibc/time.h                  |  7 +++++++
 tools/testing/selftests/nolibc/nolibc-test.c | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/tools/include/nolibc/time.h b/tools/include/nolibc/time.h
index 48f602b661b300a0bfbac5a231315fc95727c04e..fc387940d51f389d4233bd5712588dced31ae6e5 100644
--- a/tools/include/nolibc/time.h
+++ b/tools/include/nolibc/time.h
@@ -108,6 +108,13 @@ int clock_settime(clockid_t clockid, struct timespec *tp)
 }
 
 
+static __inline__
+double difftime(time_t time1, time_t time2)
+{
+	return time1 - time2;
+}
+
+
 static __attribute__((unused))
 time_t time(time_t *tptr)
 {
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index d73125c41096fd208b7b8719e61efa2da9865673..665d7631fbc6e9ecae469a4b143440ec0a43d4aa 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1304,6 +1304,17 @@ int run_syscall(int min, int max)
 	return ret;
 }
 
+int test_difftime(void)
+{
+	if (difftime(200., 100.) != 100.)
+		return 1;
+
+	if (difftime(100., 200.) != -100.)
+		return 1;
+
+	return 0;
+}
+
 int run_stdlib(int min, int max)
 {
 	int test;
@@ -1426,6 +1437,7 @@ int run_stdlib(int min, int max)
 		CASE_TEST(toupper_noop);            EXPECT_EQ(1, toupper('A'), 'A'); break;
 		CASE_TEST(abs);                     EXPECT_EQ(1, abs(-10), 10); break;
 		CASE_TEST(abs_noop);                EXPECT_EQ(1, abs(10), 10); break;
+		CASE_TEST(difftime);                EXPECT_ZR(1, test_difftime()); break;
 
 		case __LINE__:
 			return ret; /* must be last */

-- 
2.49.0