Document the problem with the Cygwin environment variable TZ.

* doc/posix-functions/tzset.texi: Add note about TZ.
* doc/posix-functions/ctime.texi: Likewise.
* doc/posix-functions/localtime.texi: Likewise.
* doc/posix-functions/mktime.texi: Likewise.
* doc/posix-functions/strftime.texi: Likewise.
* doc/posix-functions/wcsftime.texi: Likewise.
* doc/pastposix-functions/ftime.texi: Likewise.

8 files changed, 34 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index e7e29956cd..818d6e2422 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2017-04-30  Bruno Haible  <bruno@clisp.org>
 
+	Document the problem with the Cygwin environment variable TZ.
+	* doc/posix-functions/tzset.texi: Add note about TZ.
+	* doc/posix-functions/ctime.texi: Likewise.
+	* doc/posix-functions/localtime.texi: Likewise.
+	* doc/posix-functions/mktime.texi: Likewise.
+	* doc/posix-functions/strftime.texi: Likewise.
+	* doc/posix-functions/wcsftime.texi: Likewise.
+	* doc/pastposix-functions/ftime.texi: Likewise.
+
+2017-04-30  Bruno Haible  <bruno@clisp.org>
+
 	utime-tests: New module.
 	* tests/test-utime.c: New file, based on tests/test-utimens.h.
 	* tests/test-utimens-common.h: Include <sys/stat.h>.
diff --git a/doc/pastposix-functions/ftime.texi b/doc/pastposix-functions/ftime.texi
index 0fcaed1ecc..582a088163 100644
--- a/doc/pastposix-functions/ftime.texi
+++ b/doc/pastposix-functions/ftime.texi
@@ -16,6 +16,9 @@ Portability problems not fixed by Gnulib:
 This function is missing on some platforms:
 Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, IRIX 5.3, Solaris 2.4.
 @item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
+@item
 This function is marked as ``legacy'' in POSIX.  Better use @code{gettimeofday}
 or @code{clock_gettime} instead, and use @code{ftime} only as a fallback for
 portability to Windows platforms.
diff --git a/doc/posix-functions/ctime.texi b/doc/posix-functions/ctime.texi
index f5a7c27626..e54a7b5b8e 100644
--- a/doc/posix-functions/ctime.texi
+++ b/doc/posix-functions/ctime.texi
@@ -13,6 +13,9 @@ Portability problems fixed by Gnulib:
 Portability problems not fixed by Gnulib:
 @itemize
 @item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
+@item
 This function may overflow its internal buffer if an invalid year is passed.
 @item
 The @code{ctime} function need not be reentrant, and consequently is
diff --git a/doc/posix-functions/localtime.texi b/doc/posix-functions/localtime.texi
index 49a6dddc0f..1d6acdba8f 100644
--- a/doc/posix-functions/localtime.texi
+++ b/doc/posix-functions/localtime.texi
@@ -12,7 +12,11 @@ Portability problems fixed by Gnulib:
 
 Portability problems not fixed by Gnulib:
 @itemize
-@item On some platforms, this function returns nonsense values for
+@item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
+@item
+On some platforms, this function returns nonsense values for
 unsupported arguments (like @math{2^56}), rather than failing:
 FreeBSD 10.
 @end itemize
diff --git a/doc/posix-functions/mktime.texi b/doc/posix-functions/mktime.texi
index 97569480ce..ffb7b79e11 100644
--- a/doc/posix-functions/mktime.texi
+++ b/doc/posix-functions/mktime.texi
@@ -16,4 +16,7 @@ Portability problems fixed by Gnulib:
 
 Portability problems not fixed by Gnulib:
 @itemize
+@item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
 @end itemize
diff --git a/doc/posix-functions/strftime.texi b/doc/posix-functions/strftime.texi
index e58e1ef494..d371818e2e 100644
--- a/doc/posix-functions/strftime.texi
+++ b/doc/posix-functions/strftime.texi
@@ -13,6 +13,9 @@ Portability problems fixed by Gnulib:
 Portability problems not fixed by Gnulib:
 @itemize
 @item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
+@item
 The Windows C runtime library (which is used by MinGW) does not
 support the %e specifier (and possibly the other more recent SUS
 specifiers too, i.e., %C, %D, %h, %n, %r, %R, %t, and %T).
diff --git a/doc/posix-functions/tzset.texi b/doc/posix-functions/tzset.texi
index 35fc509d76..30b147cc3c 100644
--- a/doc/posix-functions/tzset.texi
+++ b/doc/posix-functions/tzset.texi
@@ -16,4 +16,7 @@ Solaris 2.6.
 
 Portability problems not fixed by Gnulib:
 @itemize
+@item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
 @end itemize
diff --git a/doc/posix-functions/wcsftime.texi b/doc/posix-functions/wcsftime.texi
index 0faa2118cf..8ab82c20a1 100644
--- a/doc/posix-functions/wcsftime.texi
+++ b/doc/posix-functions/wcsftime.texi
@@ -16,6 +16,9 @@ Portability problems not fixed by Gnulib:
 This function is missing on some platforms:
 OpenBSD 3.8, Minix 3.1.8, IRIX 5.3, Solaris 2.5.1, Cygwin 1.5.x, BeOS.
 @item
+On native Windows platforms (mingw, MSVC), this function works incorrectly
+when the environment variable @code{TZ} has been set by Cygwin.
+@item
 On AIX and Windows platforms, @code{wchar_t} is a 16-bit type and therefore cannot
 accommodate all Unicode characters.
 @end itemize