From 53ed647b224c98f74a3198215f9fa2fd1a359eb9 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Sat, 28 Mar 2009 11:10:40 +0100
Subject: configure.ac: fail when ALSA is enabled but not found

This patch adds a small autoconf M4 library which deals with
auto-detected features.  The default for those features is "auto",
which is like the old default: if the library is present on the
system, enable the feature, disable otherwise.  If the user explicitly
enables that feature (--enable-alsa), and the library is not present,
configure must fail, because it cannot fulfill the request.
---
 m4/mpd_auto.m4 | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 m4/mpd_auto.m4

(limited to 'm4')

diff --git a/m4/mpd_auto.m4 b/m4/mpd_auto.m4
new file mode 100644
index 00000000..635f4156
--- /dev/null
+++ b/m4/mpd_auto.m4
@@ -0,0 +1,40 @@
+AC_DEFUN([MPD_AUTO_ENABLED], [
+	var="enable_$1"
+	feature="$2"
+
+	if eval "test x`echo '$'$var` = xauto"; then
+		AC_MSG_NOTICE([auto-detected $feature])
+		eval "$var=yes"
+	fi
+])
+
+AC_DEFUN([MPD_AUTO_DISABLED], [
+	var="enable_$1"
+	feature="$2"
+	msg="$3"
+
+	if eval "test x`echo '$'$var` = xauto"; then
+		AC_MSG_WARN([$msg -- disabling $feature])
+		eval "$var=no"
+	else
+		AC_MSG_ERROR([$msg])
+	fi
+])
+
+AC_DEFUN([MPD_AUTO_RESULT], [
+	name="$1"
+	var="enable_$1"
+	found="found_$name"
+	feature="$2"
+	msg="$3"
+
+	if eval "test x`echo '$'$var` = xno"; then
+		eval "$found=no"
+	fi
+
+	if eval "test x`echo '$'$found` = xyes"; then
+                MPD_AUTO_ENABLED([$name], [$feature])
+	else
+                MPD_AUTO_DISABLED([$name], [$feature], [$msg])
+	fi
+])
-- 
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