# HG changeset patch
# User Bruno Haible <bruno@clisp.org>
# Date 1517385892 -3600
# Node ID c153a5913479882b4433a81c265cedabdf945bd2
# Parent  492d30539cc87385bcaed9af4fc7e6630c5f4401
environ: Fix link error on 64-bit Cygwin.

* lib/unistd.in.h (environ): On Cygwin, redeclare with the
__declspec(dllimport) attribute.
* doc/posix-functions/environ.texi: Mention the Cygwin problem.

diff -r 492d30539cc8 -r c153a5913479 ChangeLog
--- a/ChangeLog	Tue Jan 30 09:05:57 2018 +0100
+++ b/ChangeLog	Wed Jan 31 09:04:52 2018 +0100
@@ -1,3 +1,10 @@
+2018-01-31  Bruno Haible  <bruno@clisp.org>
+
+	environ: Fix link error on 64-bit Cygwin.
+	* lib/unistd.in.h (environ): On Cygwin, redeclare with the
+	__declspec(dllimport) attribute.
+	* doc/posix-functions/environ.texi: Mention the Cygwin problem.
+
 2018-01-30  Bruno Haible  <bruno@clisp.org>
 
 	get-rusage-data: Add support for Minix 3.
diff -r 492d30539cc8 -r c153a5913479 doc/posix-functions/environ.texi
--- a/doc/posix-functions/environ.texi	Tue Jan 30 09:05:57 2018 +0100
+++ b/doc/posix-functions/environ.texi	Wed Jan 31 09:04:52 2018 +0100
@@ -24,6 +24,9 @@
 #define environ (*_NSGetEnviron())
 @end smallexample
 This works at all versions of Mac OS X.
+@item
+On Cygwin in 64-bit mode, references to this variable cause a link error when
+the option @code{-Wl,--disable-auto-import} is in use.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff -r 492d30539cc8 -r c153a5913479 lib/unistd.in.h
--- a/lib/unistd.in.h	Tue Jan 30 09:05:57 2018 +0100
+++ b/lib/unistd.in.h	Wed Jan 31 09:04:52 2018 +0100
@@ -400,6 +400,13 @@
 
 
 #if @GNULIB_ENVIRON@
+# if defined __CYGWIN__
+/* The 'environ' variable is defined in a DLL. Therefore its declaration needs
+   the '__declspec(dllimport)' attribute, but the system's <unistd.h> lacks it.
+   This leads to a link error on 64-bit Cygwin when the option
+   -Wl,--disable-auto-import is in use.  */
+_GL_EXTERN_C __declspec(dllimport) char **environ;
+# endif
 # if !@HAVE_DECL_ENVIRON@
 /* Set of environment variables and values.  An array of strings of the form
    "VARIABLE=VALUE", terminated with a NULL.  */