>From 92052c44910568ef6012584a344edcb736949d2c Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Sun, 7 Mar 2021 02:21:49 +0100
Subject: [PATCH 3/9] getusershell: Optimize stdio accesses when possible.

* lib/getusershell.c: Test GNULIB_GETUSERSHELL_SINGLE_THREAD instead of
USE_UNLOCKED_IO.
* modules/getusershell (Depends-on): Add unlocked-io-internal.
* doc/multithread.texi: Document GNULIB_GETUSERSHELL_SINGLE_THREAD.
---
 ChangeLog            | 8 ++++++++
 doc/multithread.texi | 4 ++++
 lib/getusershell.c   | 2 +-
 modules/getusershell | 5 +++--
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 80d97a0..d6e8d54 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2021-03-06  Bruno Haible  <bruno@clisp.org>
 
+	getusershell: Optimize stdio accesses when possible.
+	* lib/getusershell.c: Test GNULIB_GETUSERSHELL_SINGLE_THREAD instead of
+	USE_UNLOCKED_IO.
+	* modules/getusershell (Depends-on): Add unlocked-io-internal.
+	* doc/multithread.texi: Document GNULIB_GETUSERSHELL_SINGLE_THREAD.
+
+2021-03-06  Bruno Haible  <bruno@clisp.org>
+
 	unlocked-io-internal: New module.
 	* m4/unlocked-io.m4 (gl_FUNC_GLIBC_UNLOCKED_IO): Don't define
 	USE_UNLOCKED_IO here.
diff --git a/doc/multithread.texi b/doc/multithread.texi
index 7fe19a7..a63d3ee 100644
--- a/doc/multithread.texi
+++ b/doc/multithread.texi
@@ -274,4 +274,8 @@ You may define the C macro @code{GNULIB_WCHAR_SINGLE}, if all the programs in
 your package are single-threaded and won't change the locale after it has
 been initialized.  This macro optimizes the functions @code{mbrtowc} and
 @code{wcwidth}.
+@item
+You may define the C macro @code{GNULIB_GETUSERSHELL_SINGLE_THREAD}, if all the
+programs in your package invoke the functions @code{setusershell},
+@code{getusershell}, @code{endusershell} only from a single thread.
 @end itemize
diff --git a/lib/getusershell.c b/lib/getusershell.c
index 6ae9410..be8a068 100644
--- a/lib/getusershell.c
+++ b/lib/getusershell.c
@@ -39,7 +39,7 @@
 #include "stdio--.h"
 #include "xalloc.h"
 
-#if USE_UNLOCKED_IO
+#if GNULIB_GETUSERSHELL_SINGLE_THREAD
 # include "unlocked-io.h"
 #endif
 
diff --git a/modules/getusershell b/modules/getusershell
index 26f99e5..ed2f30f 100644
--- a/modules/getusershell
+++ b/modules/getusershell
@@ -8,8 +8,9 @@ m4/getusershell.m4
 Depends-on:
 unistd
 extensions
-fopen-safer     [test $HAVE_GETUSERSHELL = 0]
-xalloc          [test $HAVE_GETUSERSHELL = 0]
+fopen-safer          [test $HAVE_GETUSERSHELL = 0]
+unlocked-io-internal [test $HAVE_GETUSERSHELL = 0]
+xalloc               [test $HAVE_GETUSERSHELL = 0]
 
 configure.ac:
 gl_FUNC_GETUSERSHELL
-- 
2.7.4