>From 2356b3663f8d08b7d3d1e4496f22dcea3c5b76b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <address@hidden>
Date: Fri, 5 Jun 2015 18:49:48 +0100
Subject: [PATCH] build: improve checks for stdbuf support

* configure.ac: Actually run the test program to
verify the constructor attribute is supported,
or when cross compiling enable -Werror so that
warnings about ignored attributes are significant.
Fixes a build failure on AIX.
---
 configure.ac | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index c159983..5e0d0ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -455,7 +455,11 @@ if test $gl_cv_list_mounted_fs = yes && test $gl_cv_fs_space = yes; then
 fi
 
 AC_MSG_CHECKING([whether this is system supports stdbuf])
-AC_COMPILE_IFELSE(
+ac_save_CFLAGS="$CFLAGS"
+# Build with -Werror to detect warnings about
+# about ignored "constructor" arguments.
+CFLAGS="$CFLAGS -Werror"
+AC_RUN_IFELSE(
   [AC_LANG_PROGRAM([[
     static int stdbuf = 0;
 
@@ -471,7 +475,20 @@ AC_COMPILE_IFELSE(
     return !(stdbuf == 1);]])
   ],
   [stdbuf_supported=yes],
-  [stdbuf_supported=no])
+  [stdbuf_supported=no],
+  [AC_COMPILE_IFELSE(
+    [AC_LANG_SOURCE([[
+      void __attribute__ ((constructor))
+      stdbuf_cross_test (void)
+      #if __ELF__
+      {}
+      #endif
+      ]])
+    ],
+    [stdbuf_supported=yes],
+    [stdbuf_supported=no])
+  ])
+CFLAGS="$ac_save_CFLAGS"
 AC_MSG_RESULT([$stdbuf_supported])
 if test "$stdbuf_supported" = "yes" && test -z "$EXEEXT"; then
   gl_ADD_PROG([optional_bin_progs], [stdbuf])
-- 
2.4.1