From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 2 Mar 2021 20:33:35 +0000 (+0100)
Subject: time-util: simplify overflow check
X-Git-Tag: v248-rc3~79
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ab05bee1dd9e59a34c2f4866a1285dc29c010904;p=thirdparty%2Fsystemd.git

time-util: simplify overflow check

And don't rely on 2s complement.
---

diff --git a/src/basic/time-util.h b/src/basic/time-util.h
index da6f3cd382c..d716074fbe3 100644
--- a/src/basic/time-util.h
+++ b/src/basic/time-util.h
@@ -155,16 +155,14 @@ usec_t jiffies_to_usec(uint32_t jiffies);
 bool in_utc_timezone(void);
 
 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 */
+        if (a > USEC_INFINITY - b) /* overflow check */
                 return USEC_INFINITY;
 
-        return c;
+        return a + b;
 }
 
 static inline usec_t usec_sub_unsigned(usec_t timestamp, usec_t delta) {