[PATCH v3] Improve the width of alternate representation for year in strftime [BZ #23758]

[TAMUKI Shoichi <tamuki at linet dot gr dot jp>]

The Japanese era name is scheduled to be changed on May 1, 2019.
Prior to this, change the alternate representation for year in
strftime to pad the number with zero to keep it constant width, so
that prevent the trouble we saw in the past from becoming obvious
again from the year after the era name changes onward.

Recently, since only one Japanese era name is used by each emperor's
reign, it is rare that the year ends in one digit or lasts more than
three digits.  In addition, the width of month, day, hour, minute, and
second is 2, so adjust the width of year the same as them, and then
the whole display balance is improved.  Therefore, it would be
reasonable to change the width padding with zero of %Ey default to 2.

Currently in glibc, besides ja_JP locale, the locales using the
conversion specifier above are lo_LA (Laos) and th_TH (Thailand).  In
these locales, they use the Buddhist era.  The Buddhist era is a value
obtained by adding 543 to the Christian era, so it is not affected by
this change of the conversion specifier %Ey.

Furthermore, for the output string of the conversion specifier %EY,
an optional flag is given to the conversion specifier so that it can
be also used the current non-padding format, and the padding format
can be controlled.  To achieve this, when an optional flag is given to
the conversion specifier %EY, the %Ey included in the combined
conversion specifier is interpreted as if decorated with the
appropriate flag.

ChangeLog:

	[BZ #23758]
	* NEWS: Mention the change.
	* manual/time.texi (strftime): Document the desctiption for %EC, %Ey,
	and %EY.
	* time/Makefile (tests): Add tst-strftime2.
	* time/strftime_l.c (__strftime_internal): Add argument yr_spec to
	override padding for %Ey.
	Change the width padding with zero of %Ey default to 2.  If an
	optional flag ('_' or '-') is specified to %EY, the %Ey in subformat
	is interpreted as if decorated with the appropriate flag.
	* time/tst-strftime2.c: New file.
---
 Changes since v2:
 - add NEWS and manual/time.texi
 - slightly modify the commit message

 NEWS                 |   7 +++
 manual/time.texi     |  15 ++++++
 time/Makefile        |   2 +-
 time/strftime_l.c    |  28 ++++++-----
 time/tst-strftime2.c | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 174 insertions(+), 12 deletions(-)
 create mode 100644 time/tst-strftime2.c

diff --git a/NEWS b/NEWS
index f488821af1..225290c56b 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,13 @@ Major new features:
   different directory.  This is a GNU extension and similar to the
   Solaris function of the same name.
 
+* Improve the width of alternate representation for year in strftime.
+  For %Ey conversion specifier, the default width is now to pad the
+  number with zero to keep minimum 2 digits as well as %y.  Also, the
+  optional flag (either _ or -) can be used for %EY, so that the
+  internal %Ey is interpreted as if decorated with the appropriate
+  flag.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * The glibc.tune tunable namespace has been renamed to glibc.cpu and the
diff --git a/manual/time.texi b/manual/time.texi
index 4d154452eb..d20a0e1bee 100644
--- a/manual/time.texi
+++ b/manual/time.texi
@@ -1393,6 +1393,9 @@ The preferred calendar time representation for the current locale.
 The century of the year.  This is equivalent to the greatest integer not
 greater than the year divided by 100.
 
+If the @code{E} modifier is specified (@code{%EC}), the locale's
+alternate representation for year (the era name) is used instead.
+
 This format was first standardized by POSIX.2-1992 and by @w{ISO C99}.
 
 @item %d
@@ -1568,10 +1571,22 @@ The preferred time of day representation for the current locale.
 The year without a century as a decimal number (range @code{00} through
 @code{99}).  This is equivalent to the year modulo 100.
 
+If the @code{E} modifier is specified (@code{%Ey}), the locale's
+alternate representation for year (the era year) is used instead.  The
+default width is to pad the number with zero to keep minimum 2 digits
+as well as @code{%y}.
+
 @item %Y
 The year as a decimal number, using the Gregorian calendar.  Years
 before the year @code{1} are numbered @code{0}, @code{-1}, and so on.
 
+If the @code{E} modifier is specified (@code{%EY}), the locale's
+alternate representation for year (generally the combination of
+@code{%EC} and @code{%Ey}) is used instead.  In this case, the
+optional flag (either @code{_} or @code{-}) can be used, so that the
+internal @code{%Ey} is interpreted as if decorated with the
+appropriate flag.
+
 @item %z
 @w{RFC 822}/@w{ISO 8601:1988} style numeric time zone (e.g.,
 @code{-0600} or @code{+0100}), or nothing if no time zone is
diff --git a/time/Makefile b/time/Makefile
index ec3e39dcea..6dc2acceaa 100644
--- a/time/Makefile
+++ b/time/Makefile
@@ -43,7 +43,7 @@ tests	:= test_time clocktest tst-posixtz tst-strptime tst_wcsftime \
 	   tst-getdate tst-mktime tst-mktime2 tst-ftime_l tst-strftime \
 	   tst-mktime3 tst-strptime2 bug-asctime bug-asctime_r bug-mktime1 \
 	   tst-strptime3 bug-getdate1 tst-strptime-whitespace tst-ftime \
-	   tst-tzname tst-y2039
+	   tst-tzname tst-y2039 tst-strftime2
 
 include ../Rules
 
diff --git a/time/strftime_l.c b/time/strftime_l.c
index c71f9f47a9..8797341ea5 100644
--- a/time/strftime_l.c
+++ b/time/strftime_l.c
@@ -434,7 +434,7 @@ static CHAR_T const month_name[][10] =
 #endif
 
 static size_t __strftime_internal (CHAR_T *, size_t, const CHAR_T *,
-				   const struct tm *, bool *
+				   const struct tm *, int *, bool *
 				   ut_argument_spec
 				   LOCALE_PARAM) __THROW;
 
@@ -456,8 +456,9 @@ my_strftime (CHAR_T *s, size_t maxsize, const CHAR_T *format,
   tmcopy = *tp;
   tp = &tmcopy;
 #endif
+  int yr_spec = 0;		/* Override padding for %Ey.  */
   bool tzset_called = false;
-  return __strftime_internal (s, maxsize, format, tp, &tzset_called
+  return __strftime_internal (s, maxsize, format, tp, &yr_spec, &tzset_called
 			      ut_argument LOCALE_ARG);
 }
 #ifdef _LIBC
@@ -466,7 +467,7 @@ libc_hidden_def (my_strftime)
 
 static size_t
 __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
-		     const struct tm *tp, bool *tzset_called
+		     const struct tm *tp, int *yr_spec, bool *tzset_called
 		     ut_argument_spec LOCALE_PARAM)
 {
 #if defined _LIBC && defined USE_IN_EXTENDED_LOCALE_MODEL
@@ -820,7 +821,7 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 	  if (modifier == L_('O'))
 	    goto bad_format;
 #ifdef _NL_CURRENT
-	  if (! (modifier == 'E'
+	  if (! (modifier == L_('E')
 		 && (*(subfmt =
 		       (const CHAR_T *) _NL_CURRENT (LC_TIME,
 						     NLW(ERA_D_T_FMT)))
@@ -838,11 +839,12 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 	  {
 	    CHAR_T *old_start = p;
 	    size_t len = __strftime_internal (NULL, (size_t) -1, subfmt,
-					      tp, tzset_called ut_argument
-					      LOCALE_ARG);
+					      tp, yr_spec, tzset_called
+					      ut_argument LOCALE_ARG);
 	    add (len, __strftime_internal (p, maxsize - i, subfmt,
-					   tp, tzset_called ut_argument
-					   LOCALE_ARG));
+					   tp, yr_spec, tzset_called
+					   ut_argument LOCALE_ARG));
+	    *yr_spec = 0;
 
 	    if (to_uppcase)
 	      while (old_start < p)
@@ -917,7 +919,7 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 #ifdef _NL_CURRENT
 	  if (! (modifier == L_('E')
 		 && (*(subfmt =
-		       (const CHAR_T *)_NL_CURRENT (LC_TIME, NLW(ERA_D_FMT)))
+		       (const CHAR_T *) _NL_CURRENT (LC_TIME, NLW(ERA_D_FMT)))
 		     != L_('\0'))))
 	    subfmt = (const CHAR_T *) _NL_CURRENT (LC_TIME, NLW(D_FMT));
 	  goto subformat;
@@ -1262,7 +1264,7 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 	  DO_NUMBER (1, tp->tm_wday);
 
 	case L_('Y'):
-	  if (modifier == 'E')
+	  if (modifier == L_('E'))
 	    {
 #if HAVE_STRUCT_ERA_ENTRY
 	      struct era_entry *era = _nl_get_era_entry (tp HELPER_LOCALE_ARG);
@@ -1273,6 +1275,8 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 # else
 		  subfmt = era->era_format;
 # endif
+		  if (pad != 0)
+		    *yr_spec = pad;
 		  goto subformat;
 		}
 #else
@@ -1294,7 +1298,9 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
 	      if (era)
 		{
 		  int delta = tp->tm_year - era->start_date[0];
-		  DO_NUMBER (1, (era->offset
+		  if (*yr_spec != 0)
+		    pad = *yr_spec;
+		  DO_NUMBER (2, (era->offset
 				 + delta * era->absolute_direction));
 		}
 #else
diff --git a/time/tst-strftime2.c b/time/tst-strftime2.c
new file mode 100644
index 0000000000..3e7ddfe9ea
--- /dev/null
+++ b/time/tst-strftime2.c
@@ -0,0 +1,134 @@
+/* Verify the behavior of strftime on alternate representation for year.
+
+   Copyright (C) 2013-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <locale.h>
+#include <time.h>
+#include <stdio.h>
+#include <string.h>
+
+static const char *locales[] = { "ja_JP.UTF-8", "lo_LA.UTF-8", "th_TH.UTF-8" };
+#define nlocales (sizeof (locales) / sizeof (locales[0]))
+
+static const char *formats[] = { "%EY", "%_EY", "%-EY" };
+#define nformats (sizeof (formats) / sizeof (formats[0]))
+
+static const struct
+{
+  const int d, m, y;
+} dates[] =
+  {
+    { 1, 3, 88 },
+    { 7, 0, 89 },
+    { 8, 0, 89 },
+    { 1, 3, 90 },
+    { 1, 3, 97 },
+    { 1, 3, 98 }
+  };
+#define ndates (sizeof (dates) / sizeof (dates[0]))
+
+static char ref[nlocales][nformats][ndates][100];
+
+static void
+mkreftable (void)
+{
+  int i, j, k;
+  char era[10];
+  static const int yrj[] = { 63, 64, 1, 2, 9, 10 };
+  static const int yrb[] = { 2531, 2532, 2532, 2533, 2540, 2541 };
+
+  for (i = 0; i < nlocales; i++)
+    for (j = 0; j < nformats; j++)
+      for (k = 0; k < ndates; k++)
+	{
+	  if (i == 0)
+	    {
+	      sprintf (era, "%s", (k < 2) ? "\xe6\x98\xad\xe5\x92\x8c"
+					  : "\xe5\xb9\xb3\xe6\x88\x90");
+	      if (yrj[k] == 1)
+		sprintf (ref[i][j][k], "%s\xe5\x85\x83\xe5\xb9\xb4", era);
+	      else
+		{
+		  if (j == 0)
+		    sprintf (ref[i][j][k], "%s%02d\xe5\xb9\xb4", era, yrj[k]);
+		  else if (j == 1)
+		    sprintf (ref[i][j][k], "%s%2d\xe5\xb9\xb4", era, yrj[k]);
+		  else
+		    sprintf (ref[i][j][k], "%s%d\xe5\xb9\xb4", era, yrj[k]);
+		}
+	    }
+	  else if (i == 1)
+	    {
+	      sprintf (era, "\xe0\xba\x9e\x2e\xe0\xba\xaa\x2e ");
+	      sprintf (ref[i][j][k], "%s%d", era, yrb[k]);
+	    }
+	  else
+	    {
+	      sprintf (era, "\xe0\xb8\x9e\x2e\xe0\xb8\xa8\x2e ");
+	      sprintf (ref[i][j][k], "%s%d", era, yrb[k]);
+	    }
+	}
+}
+
+static int
+do_test (void)
+{
+  int i, j, k, result = 0;
+  struct tm ttm;
+  char date[11], buf[100];
+  size_t r, e;
+
+  mkreftable ();
+  for (i = 0; i < nlocales; i++)
+    {
+      if (setlocale (LC_ALL, locales[i]) == NULL)
+	{
+	  printf ("locale %s does not exist, skipping...\n", locales[i]);
+	  continue;
+	}
+      printf ("[%s]\n", locales[i]);
+      for (j = 0; j < nformats; j++)
+	{
+	  for (k = 0; k < ndates; k++)
+	    {
+	      ttm.tm_mday = dates[k].d;
+	      ttm.tm_mon  = dates[k].m;
+	      ttm.tm_year = dates[k].y;
+	      strftime (date, sizeof (date), "%F", &ttm);
+	      r = strftime (buf, sizeof (buf), formats[j], &ttm);
+	      e = strlen (ref[i][j][k]);
+	      printf ("%s\t\"%s\"\t\"%s\"", date, formats[j], buf);
+	      if (strcmp (buf, ref[i][j][k]) != 0)
+		{
+		  printf ("\tshould be \"%s\"", ref[i][j][k]);
+		  if (r != e)
+		    printf ("\tgot: %zu, expected: %zu", r, e);
+		  result = 1;
+		}
+	      else
+		printf ("\tOK");
+	      putchar ('\n');
+	    }
+	  putchar ('\n');
+	}
+    }
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
-- 
2.12.2