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Re: GNULIB mktime.c compilation failure on UNICOS 9.0 Cray Y-MP EL
From: |
Paul Eggert |
Subject: |
Re: GNULIB mktime.c compilation failure on UNICOS 9.0 Cray Y-MP EL |
Date: |
Wed, 10 Nov 2004 00:28:08 -0800 |
User-agent: |
Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3 (gnu/linux) |
Thanks for reporting that. Does the following patch fix things on
your friend's Cray?
2004-11-10 Paul Eggert <address@hidden>
* mktime.c (SHR): New macro, which is a portable substitute for >>
that should work even on Crays.
Problem reported by Mark D. Baushke.
(TIME_T_MIDPOINT, ydhms_diff, __mktime_internal): Use it.
--- mktime.c.~1.43.~ 2004-10-29 15:55:02 -0700
+++ mktime.c 2004-11-10 00:16:56 -0800
@@ -45,6 +45,18 @@
# define mktime my_mktime
#endif /* DEBUG */
+/* Divide A by 2**B, truncating towards minus infinity. This is a
+ substitute for A >> B that works portably even if A is negative. A
+ and B should be free of side effects, and 0 <= B <= 30. ISO C99
+ says that A >> B has implementation-defined behavior if A is
+ negative, and some implementations (e.g., UNICOS 9.0 on a Cray Y-MP
+ EL) don't shift right in the usual way, so SHR falls back on
+ division in cases like these. */
+#define SHR(a, b) \
+ (-1 >> 1 == -1 \
+ ? (a) >> (b) \
+ : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
+
/* The extra casts work around common compiler bugs. */
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
@@ -59,14 +71,13 @@
#ifndef TIME_T_MAX
# define TIME_T_MAX TYPE_MAXIMUM (time_t)
#endif
-#define TIME_T_MIDPOINT (((TIME_T_MIN + TIME_T_MAX) >> 1) + 1)
+#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)
/* Verify a requirement at compile-time (unlike assert, which is runtime). */
#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
verify (time_t_is_integer, (time_t) 0.5 == 0);
verify (twos_complement_arithmetic, -1 == ~1 + 1);
-verify (right_shift_propagates_sign, -1 >> 1 == -1);
/* The code also assumes that signed integer overflow silently wraps
around, but this assumption can't be stated without causing a
diagnostic on some hosts. */
@@ -132,12 +143,12 @@ ydhms_diff (long int year1, long int yda
/* Compute intervening leap days correctly even if year is negative.
Take care to avoid integer overflow here. */
- int a4 = (year1 >> 2) + (TM_YEAR_BASE >> 2) - ! (year1 & 3);
- int b4 = (year0 >> 2) + (TM_YEAR_BASE >> 2) - ! (year0 & 3);
+ int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3);
+ int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3);
int a100 = a4 / 25 - (a4 % 25 < 0);
int b100 = b4 / 25 - (b4 % 25 < 0);
- int a400 = a100 >> 2;
- int b400 = b100 >> 2;
+ int a400 = SHR (a100, 2);
+ int b400 = SHR (b100, 2);
int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
/* Compute the desired time in time_t precision. Overflow might
@@ -321,14 +332,16 @@ __mktime_internal (struct tm *tp,
int LOG2_YEARS_PER_BIENNIUM = 1;
int approx_requested_biennia =
- ((year_requested >> LOG2_YEARS_PER_BIENNIUM)
- - ((EPOCH_YEAR - TM_YEAR_BASE) >> LOG2_YEARS_PER_BIENNIUM)
- + (mday >> ALOG2_DAYS_PER_BIENNIUM)
- + (hour >> ALOG2_HOURS_PER_BIENNIUM)
- + (min >> ALOG2_MINUTES_PER_BIENNIUM)
- + (LEAP_SECONDS_POSSIBLE ? 0 : sec >> ALOG2_SECONDS_PER_BIENNIUM));
+ (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM)
+ - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM)
+ + SHR (mday, ALOG2_DAYS_PER_BIENNIUM)
+ + SHR (hour, ALOG2_HOURS_PER_BIENNIUM)
+ + SHR (min, ALOG2_MINUTES_PER_BIENNIUM)
+ + (LEAP_SECONDS_POSSIBLE
+ ? 0
+ : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM)));
- int approx_biennia = t0 >> ALOG2_SECONDS_PER_BIENNIUM;
+ int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM);
int diff = approx_biennia - approx_requested_biennia;
int abs_diff = diff < 0 ? - diff : diff;
@@ -346,7 +359,7 @@ __mktime_internal (struct tm *tp,
/* Overflow occurred. Try repairing it; this might work if
the time zone offset is enough to undo the overflow. */
time_t repaired_t0 = -1 - t0;
- approx_biennia = repaired_t0 >> ALOG2_SECONDS_PER_BIENNIUM;
+ approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM);
diff = approx_biennia - approx_requested_biennia;
abs_diff = diff < 0 ? - diff : diff;
if (overflow_threshold < abs_diff)