Documentation to the above changes (bug 10871).

	[BZ #10871]
	* manual/locale.texi: Document ALTMON_1..12 constants for
	nl_langinfo.  Specify when to use ALTMON instead of MON.
	* manual/time.texi (strftime, strptime): Document GNU extension
	permitting O modifier with %B and %b.  Specify when to use
	%OB instead of %B.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

4 files changed, 83 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index ab15b5991c..7b518b269a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,15 @@
 2018-01-22  Rafal Luzynski  <digitalfreak@lingonborough.com>
 
 	[BZ #10871]
+	* manual/locale.texi: Document ALTMON_1..12 constants for
+	nl_langinfo.  Specify when to use ALTMON instead of MON.
+	* manual/time.texi (strftime, strptime): Document GNU extension
+	permitting O modifier with %B and %b.  Specify when to use
+	%OB instead of %B.
+
+2018-01-22  Rafal Luzynski  <digitalfreak@lingonborough.com>
+
+	[BZ #10871]
 	* locale/C-time.c (_nl_C_LC_TIME): Add abbreviated alternative month
 	names, define them as the same as abbreviated month names explicitly.
 	* locale/categories.def (LC_TIME): Add ab_alt_mon and wide-ab_alt_mon.
diff --git a/NEWS b/NEWS
index 79736dbee8..dd8b7956b2 100644
--- a/NEWS
+++ b/NEWS
@@ -69,6 +69,30 @@ Major new features:
   collation ordering.  Previous glibc versions used locale-specific
   ordering, the change might break systems that relied on that.
 
+* Support for two grammatical forms of month names has been added.
+  In a call to strftime, the "%B" and "%b" format specifiers will now
+  produce the grammatical form required when the month is used as part
+  of a complete date.  New "%OB" and "%Ob" specifiers produce the form
+  required when the month is named by itself.  For instance, in Greek
+  and in many Slavic and Baltic languages, "%B" will produce the month
+  in genitive case, and "%OB" will produce the month in nominative case.
+
+  In a call to strptime, "%B", "%b", "%h", "%OB", "%Ob", and "%Oh"
+  are all valid and will all accept any known form of month
+  name---standalone or complete, abbreviated or full.  In a call to
+  nl_langinfo, the query constants MON_1..12 and ABMON_1..12 return
+  the strings used by "%B" and "%b", respectively.  New query
+  constants ALTMON_1..12 and _NL_ABALTMON_1..12 return the strings
+  used by "%OB" and "%Ob", respectively.
+
+  In a locale definition file, use "alt_mon" and "ab_alt_mon" to
+  define the strings for %OB and %Ob, respectively; these have the
+  same syntax as "mon" and "ab_mon".
+
+  This feature is currently a GNU extension, but it is expected to
+  be added to the next revision of POSIX, and it is also already
+  available on some BSD-derived operating systems.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * Support for statically linked applications which call dlopen is deprecated
diff --git a/manual/locale.texi b/manual/locale.texi
index 60ad2a1e40..059db75c1c 100644
--- a/manual/locale.texi
+++ b/manual/locale.texi
@@ -923,7 +923,7 @@ corresponds to Sunday.
 @itemx DAY_5
 @itemx DAY_6
 @itemx DAY_7
-Similar to @code{ABDAY_1} etc., but here the return value is the
+Similar to @code{ABDAY_1} etc.,@: but here the return value is the
 unabbreviated weekday name.
 @item ABMON_1
 @itemx ABMON_2
@@ -937,7 +937,8 @@ unabbreviated weekday name.
 @itemx ABMON_10
 @itemx ABMON_11
 @itemx ABMON_12
-The return value is abbreviated name of the month.  @code{ABMON_1}
+The return value is the abbreviated name of the month, in the grammatical
+form used when the month forms part of a complete date.  @code{ABMON_1}
 corresponds to January.
 @item MON_1
 @itemx MON_2
@@ -951,8 +952,27 @@ corresponds to January.
 @itemx MON_10
 @itemx MON_11
 @itemx MON_12
-Similar to @code{ABMON_1} etc., but here the month names are not abbreviated.
+Similar to @code{ABMON_1} etc.,@: but here the month names are not abbreviated.
 Here the first value @code{MON_1} also corresponds to January.
+@item ALTMON_1
+@itemx ALTMON_2
+@itemx ALTMON_3
+@itemx ALTMON_4
+@itemx ALTMON_5
+@itemx ALTMON_6
+@itemx ALTMON_7
+@itemx ALTMON_8
+@itemx ALTMON_9
+@itemx ALTMON_10
+@itemx ALTMON_11
+@itemx ALTMON_12
+Similar to @code{MON_1} etc.,@: but here the month names are in the grammatical
+form used when the month is named by itself.  The @code{strftime} functions
+use these month names for the format specifier @code{OB}.
+
+Note that not all languages need two different forms of the month names,
+so the strings returned for @code{MON_@dots{}} and @code{ALTMON_@dots{}}
+may or may not be the same, depending on the locale.
 @item AM_STR
 @itemx PM_STR
 The return values are strings which can be used in the representation of time
diff --git a/manual/time.texi b/manual/time.texi
index 33aa221428..2a5afd9e56 100644
--- a/manual/time.texi
+++ b/manual/time.texi
@@ -1346,8 +1346,13 @@ example, @code{%Ex} might yield a date format based on the Japanese
 Emperors' reigns.
 
 @item O
-Use the locale's alternate numeric symbols for numbers.  This modifier
-applies only to numeric format specifiers.
+With all format specifiers that produce numbers: use the locale's
+alternate numeric symbols.
+
+With @code{%B} and @code{%b}: use the grammatical form for month names
+that is appropriate when the month is named by itself, rather than
+the form that is appropriate when the month is used as part of a
+complete date.  This is a GNU extension.
 @end table
 
 If the format supports the modifier but no alternate representation
@@ -1365,13 +1370,21 @@ The abbreviated weekday name according to the current locale.
 The full weekday name according to the current locale.
 
 @item %b
-The abbreviated month name according to the current locale.
+The abbreviated month name according to the current locale, in the
+grammatical form used when the month is part of a complete date.
+As a GNU extension, the @code{O} modifier can be used (@code{%Ob})
+to get the grammatical form used when the month is named by itself.
 
 @item %B
-The full month name according to the current locale.
+The full month name according to the current locale, in the
+grammatical form used when the month is part of a complete date.
+As a GNU extension, the @code{O} modifier can be used (@code{%OB})
+to get the grammatical form used when the month is named by itself.
 
-Using @code{%B} together with @code{%d} produces grammatically
-incorrect results for some locales.
+Note that not all languages need two different forms of the month
+names, so the text produced by @code{%B} and @code{%OB}, and by
+@code{%b} and @code{%Ob}, may or may not be the same, depending on
+the locale.
 
 @item %c
 The preferred calendar time representation for the current locale.
@@ -1778,8 +1791,14 @@ the full name.
 @item %b
 @itemx %B
 @itemx %h
-The month name according to the current locale, in abbreviated form or
-the full name.
+A month name according to the current locale.  All three specifiers
+will recognize both abbreviated and full month names.  If the
+locale provides two different grammatical forms of month names,
+all three specifiers will recognize both forms.
+
+As a GNU extension, the @code{O} modifier can be used with these
+specifiers; it has no effect, as both grammatical forms of month
+names are recognized.
 
 @item %c
 The date and time representation for the current locale.