util: add check that makes sure time_t and TIME_T_MAX work the way we assume they do

2 files changed, 11 insertions, 1 deletions

diff --git a/src/basic/time-util.h b/src/basic/time-util.h
index b37d5ad5dc..9c7758a959 100644
--- a/src/basic/time-util.h
+++ b/src/basic/time-util.h
@@ -69,7 +69,7 @@ typedef struct dual_timestamp {
 #define FORMAT_TIMESTAMP_RELATIVE_MAX 256
 #define FORMAT_TIMESPAN_MAX 64
 
-#define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)
+#define TIME_T_MAX (time_t)((UINTMAX_C(1) << ((sizeof(time_t) << 3) - 1)) - 1)
 
 #define DUAL_TIMESTAMP_NULL ((struct dual_timestamp) { 0ULL, 0ULL })
 
diff --git a/src/test/test-time.c b/src/test/test-time.c
index ca44f81f9c..254a8d0e52 100644
--- a/src/test/test-time.c
+++ b/src/test/test-time.c
@@ -192,6 +192,8 @@ static void test_usec_add(void) {
 }
 
 int main(int argc, char *argv[]) {
+        uintmax_t x;
+
         test_parse_sec();
         test_parse_time();
         test_parse_nsec();
@@ -202,5 +204,13 @@ int main(int argc, char *argv[]) {
         test_get_timezones();
         test_usec_add();
 
+        /* Ensure time_t is signed */
+        assert_cc((time_t) -1 < (time_t) 1);
+
+        /* Ensure TIME_T_MAX works correctly */
+        x = (uintmax_t) TIME_T_MAX;
+        x ++;
+        assert((time_t) x < 0);
+
         return 0;
 }