[PATCH] timespec-add, timespec-sub: simplify

[Paul Eggert]

* lib/timespec-add.c (timespec_add):
* lib/timespec-sub.c (timespec_sub):
Simplify, now that INT_ADD_WRAPV and INT_SUBTRACT_WRAPV
work on unsigned integers.
---
 ChangeLog          |  8 ++++++++
 lib/timespec-add.c | 20 +++++++-------------
 lib/timespec-sub.c | 20 +++++++-------------
 3 files changed, 22 insertions(+), 26 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 804294150..2469945b4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-10-24  Paul Eggert  <address@hidden>
+
+       timespec-add, timespec-sub: simplify
+       * lib/timespec-add.c (timespec_add):
+       * lib/timespec-sub.c (timespec_sub):
+       Simplify, now that INT_ADD_WRAPV and INT_SUBTRACT_WRAPV
+       work on unsigned integers.
+
 2019-10-23  Paul Eggert  <address@hidden>
 
        nstrftime: speed up integer overflow checking
diff --git a/lib/timespec-add.c b/lib/timespec-add.c
index e0a9f12e1..abee15482 100644
--- a/lib/timespec-add.c
+++ b/lib/timespec-add.c
@@ -33,36 +33,30 @@ timespec_add (struct timespec a, struct timespec b)
   int ns = a.tv_nsec + b.tv_nsec;
   int nsd = ns - TIMESPEC_HZ;
   int rns = ns;
-  time_t tmin = TYPE_MINIMUM (time_t);
-  time_t tmax = TYPE_MAXIMUM (time_t);
 
   if (0 <= nsd)
     {
       rns = nsd;
-      if (bs < tmax)
-        bs++;
+      time_t bs1;
+      if (!INT_ADD_WRAPV (bs, 1, &bs1))
+        bs = bs1;
       else if (rs < 0)
         rs++;
       else
         goto high_overflow;
     }
 
-  /* INT_ADD_WRAPV is not appropriate since time_t might be unsigned.
-     In theory time_t might be narrower than int, so plain
-     INT_ADD_OVERFLOW does not suffice.  */
-  if (! INT_ADD_OVERFLOW (rs, bs) && tmin <= rs + bs && rs + bs <= tmax)
-    rs += bs;
-  else
+  if (INT_ADD_WRAPV (rs, bs, &rs))
     {
-      if (rs < 0)
+      if (bs < 0)
         {
-          rs = tmin;
+          rs = TYPE_MINIMUM (time_t);
           rns = 0;
         }
       else
         {
         high_overflow:
-          rs = tmax;
+          rs = TYPE_MAXIMUM (time_t);
           rns = TIMESPEC_HZ - 1;
         }
     }
diff --git a/lib/timespec-sub.c b/lib/timespec-sub.c
index 48434e815..77b9353df 100644
--- a/lib/timespec-sub.c
+++ b/lib/timespec-sub.c
@@ -33,36 +33,30 @@ timespec_sub (struct timespec a, struct timespec b)
   time_t bs = b.tv_sec;
   int ns = a.tv_nsec - b.tv_nsec;
   int rns = ns;
-  time_t tmin = TYPE_MINIMUM (time_t);
-  time_t tmax = TYPE_MAXIMUM (time_t);
 
   if (ns < 0)
     {
       rns = ns + TIMESPEC_HZ;
-      if (bs < tmax)
-        bs++;
+      time_t bs1;
+      if (!INT_ADD_WRAPV (bs, 1, &bs1))
+        bs = bs1;
       else if (- TYPE_SIGNED (time_t) < rs)
         rs--;
       else
         goto low_overflow;
     }
 
-  /* INT_SUBTRACT_WRAPV is not appropriate since time_t might be unsigned.
-     In theory time_t might be narrower than int, so plain
-     INT_SUBTRACT_OVERFLOW does not suffice.  */
-  if (! INT_SUBTRACT_OVERFLOW (rs, bs) && tmin <= rs - bs && rs - bs <= tmax)
-    rs -= bs;
-  else
+  if (INT_SUBTRACT_WRAPV (rs, bs, &rs))
     {
-      if (rs < 0)
+      if (0 < bs)
         {
         low_overflow:
-          rs = tmin;
+          rs = TYPE_MINIMUM (time_t);
           rns = 0;
         }
       else
         {
-          rs = tmax;
+          rs = TYPE_MAXIMUM (time_t);
           rns = TIMESPEC_HZ - 1;
         }
     }
-- 
2.21.0