From bb89f0e94f82f1afc243a7f26eff92363eaf9d8d Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 3 Feb 2015 00:15:28 +1100
Subject: [PATCH] m4: bump m4 dependencies

---
 m4/nc_append_one_compile_flag.m4 | 25 +++++++++++++++++++++++++
 m4/nc_cxx.m4                     |  6 +++++-
 m4/nc_debugging.m4               |  3 ++-
 3 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 m4/nc_append_one_compile_flag.m4

diff --git a/m4/nc_append_one_compile_flag.m4 b/m4/nc_append_one_compile_flag.m4
new file mode 100644
index 00000000..967dd0ec
--- /dev/null
+++ b/m4/nc_append_one_compile_flag.m4
@@ -0,0 +1,25 @@
+# SYNOPSIS
+#
+#   NC_APPEND_ONE_COMPILE_FLAG([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS])
+#
+# DESCRIPTION
+#
+#   Append the first valid compilation flag in the provided list to FLAGS-VARIABLE
+
+
+AC_DEFUN([NC_APPEND_ONE_COMPILE_FLAG], [
+    AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+
+    for __dummy in "1"; do
+        for flag in $1; do
+            AX_CHECK_COMPILE_FLAG([$flag],
+                                  [AX_APPEND_FLAG([$flag], [$2])
+                                   break 2],
+                                  [],
+                                  [$3])
+        done
+
+        AC_MSG_ERROR([unable to find a valid compilation flag in '$1'])
+    done
+])
diff --git a/m4/nc_cxx.m4 b/m4/nc_cxx.m4
index 06dbd898..7e675ab3 100644
--- a/m4/nc_cxx.m4
+++ b/m4/nc_cxx.m4
@@ -1,5 +1,9 @@
 AC_DEFUN([NC_CXX],[
-    AX_APPEND_COMPILE_FLAGS([-std=c++1y])
+    AX_CHECK_COMPILE_FLAG(
+        [-std=c++1y],
+        [AX_APPEND_FLAG([-std=c++1y], [CXXFLAGS])],
+        [AC_ERROR([Unable to enable c++1y])]
+    )
 
     AX_APPEND_COMPILE_FLAGS([-fno-deduce-init-list], [], [-Werror])
     AX_APPEND_COMPILE_FLAGS([-fno-deduce-init-list], [], [-Werror])
diff --git a/m4/nc_debugging.m4 b/m4/nc_debugging.m4
index 4d53ab6e..8527dc6b 100644
--- a/m4/nc_debugging.m4
+++ b/m4/nc_debugging.m4
@@ -3,6 +3,7 @@ AC_DEFUN([NC_DEBUGGING],[
     AX_REQUIRE_DEFINED([AS_HELP_STRING])
     AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
     AX_REQUIRE_DEFINED([AX_APPEND_LINK_FLAGS])
+    AX_REQUIRE_DEFINED([NC_APPEND_ONE_COMPILE_FLAG])
 
     ##-------------------------------------------------------------------------
     AC_ARG_ENABLE([sanitizer], [
@@ -31,7 +32,7 @@ AC_DEFUN([NC_DEBUGGING],[
         AC_DEFINE([ENABLE_DEBUGGING], [], [Debugging support enabled])
         AC_DEFINE([_GLIBCXX_DEBUG],   [], [Use glibcxx debugging mode])
 
-        AX_APPEND_COMPILE_FLAGS([-O0])
+        NC_APPEND_ONE_COMPILE_FLAG([-O0])
     ], [
         AX_APPEND_COMPILE_FLAGS([-O2])
     ])