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

[thirdparty/systemd.git] / src / basic / time-util.h

diff --git a/src/basic/time-util.h b/src/basic/time-util.h
index 0417c29cddbe4b5506745a190e42f9fc1f0b5bcb..9c7758a9596802a423994618b0644d7e056481f7 100644 (file)
--- a/src/basic/time-util.h
+++ b/src/basic/time-util.h
@@ -22,6 +22,9 @@
 ***/
 
 #include <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <time.h>
 
@@ -66,7 +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 })
 
@@ -124,3 +127,16 @@ time_t mktime_or_timegm(struct tm *tm, bool utc);
 struct tm *localtime_or_gmtime_r(const time_t *t, struct tm *tm, bool utc);
 
 unsigned long usec_to_jiffies(usec_t usec);
+
+static inline usec_t usec_add(usec_t a, usec_t b) {
+        usec_t c;
+
+        /* Adds two time values, and makes sure USEC_INFINITY as input results as USEC_INFINITY in output, and doesn't
+         * overflow. */
+
+        c = a + b;
+        if (c < a || c < b) /* overflow check */
+                return USEC_INFINITY;
+
+        return c;
+}