>From a680228fe4d39f749cb819e45202c6fec6ca9d29 Mon Sep 17 00:00:00 2001
From: Bruno Haible <address@hidden>
Date: Sat, 8 Feb 2020 20:38:01 +0100
Subject: [PATCH 1/3] fchmodat: Improve cross-compilation guesses.

* m4/fchmodat.m4 (gl_FUNC_FCHMODAT): Require AC_CANONICAL_HOST. When
cross-compiling, guess depending on the platform.
* doc/posix-functions/fchmodat.texi: Clarify.
---
 ChangeLog                         |  7 +++++++
 doc/posix-functions/fchmodat.texi | 10 +++++-----
 m4/fchmodat.m4                    | 14 +++++++++++---
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index df48e88..32d9a00 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2020-02-08  Bruno Haible  <address@hidden>
 
+	fchmodat: Improve cross-compilation guesses.
+	* m4/fchmodat.m4 (gl_FUNC_FCHMODAT): Require AC_CANONICAL_HOST. When
+	cross-compiling, guess depending on the platform.
+	* doc/posix-functions/fchmodat.texi: Clarify.
+
+2020-02-08  Bruno Haible  <address@hidden>
+
 	Fix compilation errors in a testdir created with --with-c++-tests.
 	* lib/c++defs.h (_GL_CXXALIASWARN1_2): Do not use __typeof__ (func),
 	since it does not work any more with g++ >= 4.4.
diff --git a/doc/posix-functions/fchmodat.texi b/doc/posix-functions/fchmodat.texi
index 4d19031..a295f83 100644
--- a/doc/posix-functions/fchmodat.texi
+++ b/doc/posix-functions/fchmodat.texi
@@ -9,15 +9,15 @@ Gnulib module: fchmodat
 Portability problems fixed by Gnulib:
 @itemize
 @item
-When given the @code{AT_SYMLINK_NOFOLLOW} flag,
-this function fails with @code{errno} set to @code{ENOTSUP},
-even when the file is not a symbolic link:
-GNU/Linux and Cygwin with glibc 2.31.
-@item
 This function is missing on some platforms:
 glibc 2.3.6, Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8,
 AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14.
 But the replacement function is not safe to be used in libraries and is not multithread-safe.
+@item
+When given the @code{AT_SYMLINK_NOFOLLOW} flag,
+this function fails with @code{errno} set to @code{ENOTSUP},
+even when the file is not a symbolic link:
+GNU/Linux with glibc 2.31, Cygwin 2.9.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/m4/fchmodat.m4 b/m4/fchmodat.m4
index 8195ef6..f284485 100644
--- a/m4/fchmodat.m4
+++ b/m4/fchmodat.m4
@@ -1,4 +1,4 @@
-# fchmodat.m4 serial 2
+# fchmodat.m4 serial 3
 dnl Copyright (C) 2004-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -10,6 +10,7 @@ AC_DEFUN([gl_FUNC_FCHMODAT],
 [
   AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
   AC_CHECK_FUNCS_ONCE([fchmodat lchmod])
   if test $ac_cv_func_fchmodat != yes; then
     HAVE_FCHMODAT=0
@@ -17,7 +18,9 @@ AC_DEFUN([gl_FUNC_FCHMODAT],
     AC_CACHE_CHECK(
       [whether fchmodat+AT_SYMLINK_NOFOLLOW works on non-symlinks],
       [gl_cv_func_fchmodat_works],
-      [AC_RUN_IFELSE(
+      [dnl This test fails on GNU/Linux with glibc 2.31 (but not on
+       dnl GNU/kFreeBSD nor GNU/Hurd) and Cygwin 2.9.
+       AC_RUN_IFELSE(
          [AC_LANG_PROGRAM(
             [
               AC_INCLUDES_DEFAULT[
@@ -53,7 +56,12 @@ AC_DEFUN([gl_FUNC_FCHMODAT],
             ]])],
          [gl_cv_func_fchmodat_works=yes],
          [gl_cv_func_fchmodat_works=no],
-         [gl_cv_func_fchmodat_works=$gl_cross_guess_normal])
+         [case "$host_os" in
+            dnl Guess no on Linux with glibc and Cygwin, yes otherwise.
+            linux-gnu* | cygwin*) gl_cv_func_fchmodat_works="guessing no" ;;
+            *)                    gl_cv_func_fchmodat_works="$gl_cross_guess_normal" ;;
+          esac
+         ])
        rm -f conftest.fchmodat])
     case $gl_cv_func_fchmodat_works in
       *yes) ;;
-- 
2.7.4