added memory poisoning library

Memory poisoning is useful for marking memory regions as "undefined".
This poisoning only enabled in the debug build (!NDEBUG).

Makefile.am

@@ -107,6 +107,7 @@ mpd_headers = \
 	src/playlist_print.h \
 	src/playlist_save.h \
 	src/playlist_state.h \
+	src/poison.h \
 	src/riff.h \
 	src/aiff.h \
 	src/queue.h \

src/poison.h

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef MPD_POISON_H
+#define MPD_POISON_H
+
+#ifndef NDEBUG
+#include <string.h>
+#endif
+
+/**
+ * Poisons the specified memory area and marks it as "not accessible".
+ *
+ * @param p pointer to the memory area
+ * @param length number of bytes to poison
+ */
+static inline void
+poison_noaccess(void *p, size_t length)
+{
+#ifdef NDEBUG
+	(void)p;
+	(void)length;
+#else
+	memset(p, 0x01, length);
+#endif
+}
+
+/**
+ * Poisons the specified memory area and marks it as "not defined".
+ *
+ * @param p pointer to the memory area
+ * @param length number of bytes to poison
+ */
+static inline void
+poison_undefined(void *p, size_t length)
+{
+#ifdef NDEBUG
+	(void)p;
+	(void)length;
+#else
+	memset(p, 0x02, length);
+#endif
+}
+
+
+#endif