autotools: Add macros for AX_APPEND_COMPILE_FLAGS
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/m4/ax_append_compile_flags.m4 b/m4/ax_append_compile_flags.m4
new file mode 100644
index 0000000..5b6f1af
--- /dev/null
+++ b/m4/ax_append_compile_flags.m4
@@ -0,0 +1,67 @@
+# ============================================================================
+# https://www.gnu.org/software/autoconf-archive/ax_append_compile_flags.html
+# ============================================================================
+#
+# SYNOPSIS
+#
+# AX_APPEND_COMPILE_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+# For every FLAG1, FLAG2 it is checked whether the compiler works with the
+# flag. If it does, the flag is added FLAGS-VARIABLE
+#
+# If FLAGS-VARIABLE is not specified, the current language's flags (e.g.
+# CFLAGS) is used. During the check the flag is always added to the
+# current language's flags.
+#
+# If EXTRA-FLAGS is defined, it is added to the current language's default
+# flags (e.g. CFLAGS) when the check is done. The check is thus made with
+# the flags: "CFLAGS EXTRA-FLAGS FLAG". This can for example be used to
+# force the compiler to issue an error when a bad flag is given.
+#
+# INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+# NOTE: This macro depends on the AX_APPEND_FLAG and
+# AX_CHECK_COMPILE_FLAG. Please keep this macro in sync with
+# AX_APPEND_LINK_FLAGS.
+#
+# LICENSE
+#
+# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your
+# option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+# Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+# As a special exception, the respective Autoconf Macro's copyright owner
+# gives unlimited permission to copy, distribute and modify the configure
+# scripts that are the output of Autoconf when processing the Macro. You
+# need not follow the terms of the GNU General Public License when using
+# or distributing such scripts, even though portions of the text of the
+# Macro appear in them. The GNU General Public License (GPL) does govern
+# all other use of the material that constitutes the Autoconf Macro.
+#
+# This special exception to the GPL applies to versions of the Autoconf
+# Macro released by the Autoconf Archive. When you make and distribute a
+# modified version of the Autoconf Macro, you may extend this special
+# exception to the GPL to apply to your modified version as well.
+
+#serial 6
+
+AC_DEFUN([AX_APPEND_COMPILE_FLAGS],
+[AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+for flag in $1; do
+ AX_CHECK_COMPILE_FLAG([$flag], [AX_APPEND_FLAG([$flag], [$2])], [], [$3], [$4])
+done
+])dnl AX_APPEND_COMPILE_FLAGS