[Bug-gnulib] more porting of code containing >> to Crays

[Paul Eggert]

Inspired by the recent changes to mktime.c for right-shift on Crays, I
installed similar changes to getdate.y, strftime.c, and quotearg.c.
This is both for gnulib and for coreutils:

2004-11-10  Paul Eggert  <address@hidden>

        * lib/getdate.y (SHR): New macro, which is a portable
        substitute for >> that should work even on Crays.
        (tm_diff): Use it.
        * lib/strftime.c (SHR): Likewise.
        (tm_diff): Use it.
        * lib/quotearg.c (struct quoting_options): Use unsigned int for
        quote_these_too, so that right shifts are well defined.  All uses
        changed.

Index: lib/getdate.y
===================================================================
RCS file: /fetish/cu/lib/getdate.y,v
retrieving revision 1.88
diff -p -u -r1.88 getdate.y
--- lib/getdate.y       3 Nov 2004 08:54:51 -0000       1.88
+++ lib/getdate.y       11 Nov 2004 05:49:17 -0000
@@ -84,6 +84,21 @@
 # define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
 #endif
 
+/* Shift A right by B bits portably, by dividing A by 2**B and
+   truncating towards minus infinity.  A and B should be free of side
+   effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
+   INT_BITS is the number of useful bits in an int.  GNU code can
+   assume that INT_BITS is at least 32.
+
+   ISO C99 says that A >> B is implementation-defined if A < 0.  Some
+   implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
+   right in the usual way when A < 0, so SHR falls back on division if
+   ordinary A >> B doesn't seem to be the usual signed shift.  */
+#define SHR(a, b)      \
+  (-1 >> 1 == -1       \
+   ? (a) >> (b)                \
+   : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
+
 #define EPOCH_YEAR 1970
 #define TM_YEAR_BASE 1900
 
@@ -734,12 +749,12 @@ tm_diff (struct tm const *a, struct tm c
 {
   /* Compute intervening leap days correctly even if year is negative.
      Take care to avoid int overflow in leap day calculations.  */
-  int a4 = (a->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (a->tm_year & 3);
-  int b4 = (b->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (b->tm_year & 3);
+  int a4 = SHR (a->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (a->tm_year & 3);
+  int b4 = SHR (b->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (b->tm_year & 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);
   long int ayear = a->tm_year;
   long int years = ayear - b->tm_year;
Index: lib/strftime.c
===================================================================
RCS file: /fetish/cu/lib/strftime.c,v
retrieving revision 1.77
diff -p -u -r1.77 strftime.c
--- lib/strftime.c      9 Nov 2004 20:54:43 -0000       1.77
+++ lib/strftime.c      11 Nov 2004 05:49:17 -0000
@@ -104,6 +104,21 @@ extern char *tzname[];
 # endif
 #endif
 
+/* Shift A right by B bits portably, by dividing A by 2**B and
+   truncating towards minus infinity.  A and B should be free of side
+   effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
+   INT_BITS is the number of useful bits in an int.  GNU code can
+   assume that INT_BITS is at least 32.
+
+   ISO C99 says that A >> B is implementation-defined if A < 0.  Some
+   implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
+   right in the usual way when A < 0, so SHR falls back on division if
+   ordinary A >> B doesn't seem to be the usual signed shift.  */
+#define SHR(a, b)      \
+  (-1 >> 1 == -1       \
+   ? (a) >> (b)                \
+   : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
+
 #define TYPE_SIGNED(t) ((t) -1 < 0)
 
 /* Bound on length of the string representing an integer value of type t.
@@ -279,12 +294,12 @@ tm_diff (const struct tm *a, const struc
   /* Compute intervening leap days correctly even if year is negative.
      Take care to avoid int overflow in leap day calculations,
      but it's OK to assume that A and B are close to each other.  */
-  int a4 = (a->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (a->tm_year & 3);
-  int b4 = (b->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (b->tm_year & 3);
+  int a4 = SHR (a->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (a->tm_year & 3);
+  int b4 = SHR (b->tm_year, 2) + SHR (TM_YEAR_BASE, 2) - ! (b->tm_year & 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);
   int years = a->tm_year - b->tm_year;
   int days = (365 * years + intervening_leap_days
Index: lib/quotearg.c
===================================================================
RCS file: /fetish/cu/lib/quotearg.c,v
retrieving revision 1.43
diff -p -u -r1.43 quotearg.c
--- lib/quotearg.c      2 Aug 2004 22:52:17 -0000       1.43
+++ lib/quotearg.c      11 Nov 2004 05:49:17 -0000
@@ -84,7 +84,7 @@ struct quoting_options
 
   /* Quote the characters indicated by this bit vector even if the
      quoting style would not normally require them to be quoted.  */
-  int quote_these_too[(UCHAR_MAX / INT_BITS) + 1];
+  unsigned int quote_these_too[(UCHAR_MAX / INT_BITS) + 1];
 };
 
 /* Names of quoting styles.  */
@@ -152,7 +152,8 @@ int
 set_char_quoting (struct quoting_options *o, char c, int i)
 {
   unsigned char uc = c;
-  int *p = (o ? o : &default_quoting_options)->quote_these_too + uc / INT_BITS;
+  unsigned int *p =
+    (o ? o : &default_quoting_options)->quote_these_too + uc / INT_BITS;
   int shift = uc % INT_BITS;
   int r = (*p >> shift) & 1;
   *p ^= ((i & 1) ^ r) << shift;