diff --git a/gpgme/debug.h b/gpgme/debug.h
new file mode 100644
index 00000000..bdeaebcb
--- /dev/null
+++ b/gpgme/debug.h
@@ -0,0 +1,110 @@
+/* debug.h - interface to debugging functions
+ *      Copyright (C) 2002 g10 Code GmbH
+ *
+ * This file is part of GPGME.
+ *
+ * GPGME 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.
+ *
+ * GPGME 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 DEBUG_H
+#define DEBUG_H
+
+/* Log the formatted string FORMAT at debug level LEVEL or higher.  */
+void _gpgme_debug (int level, const char *format, ...);
+
+/* Start a new debug line in *LINE, logged at level LEVEL or higher,
+   and starting with the formatted string FORMAT.  */
+void _gpgme_debug_begin (void **helper, int level, const char *format, ...);
+
+/* Add the formatted string FORMAT to the debug line *LINE.  */
+void _gpgme_debug_add (void **helper, const char *format, ...);
+
+/* Finish construction of *LINE and send it to the debug output
+   stream.  */
+void _gpgme_debug_end (void **helper);
+
+/* Indirect stringification, requires __STDC__ to work.  */
+#define STRINGIFY(v) #v
+#define XSTRINGIFY(v) STRINGIFY(v)
+
+#if 0
+/* Only works in GNU.  */
+#define DEBUG(fmt, arg...) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__) , ##arg)
+#define DEBUG_BEGIN(hlp, lvl, fmt, arg...) \
+  _gpgme_debug_begin (&(hlp), lvl, "%s:%s: " fmt, __FILE__, \
+		      XSTRINGIFY (__LINE__) , ##arg)
+#define DEBUG_ADD(hlp, fmt, arg...) \
+  _gpgme_debug_add (&(hlp), fmt , ##arg)
+#define DEBUG_END(hlp, fmt, arg...) \
+  _gpgme_debug_add (&(hlp), fmt , ##arg); \
+  _gpgme_debug_end (&(hlp))
+#elsif 0
+/* Only works in C99.  */
+#define DEBUG0(fmt) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__))
+#define DEBUG(fmt, ...) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), __VA_ARGS__)
+#define DEBUG_BEGIN(hlp, lvl, fmt) \
+  _gpgme_debug_begin (&(hlp), lvl, "%s:%s: " fmt, __FILE__, \
+		      XSTRINGIFY (__LINE__))
+#define DEBUG_BEGINX(hlp, lvl, fmt, ...) \
+  _gpgme_debug_begin (&(hlp), lvl, "%s:%s: " fmt, __FILE__, \
+		      XSTRINGIFY (__LINE__), __VA_ARGS__)
+#define DEBUG_ADD0(hlp, fmt) \
+  _gpgme_debug_add (&(hlp), fmt)
+#define DEBUG_ADD(hlp, fmt, ...) \
+  _gpgme_debug_add (&(hlp), fmt, __VA_ARGS__)
+#define DEBUG_END(hlp, fmt) \
+  _gpgme_debug_add (&(hlp), fmt); \
+  _gpgme_debug_end (&(hlp))
+#define DEBUG_ENDX(hlp, fmt, ...) \
+  _gpgme_debug_add (&(hlp), fmt, __VA_ARGS__); \
+  _gpgme_debug_end (&(hlp))
+#else
+/* This finally works everywhere, horror.  */
+#define DEBUG0(fmt) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__))
+#define DEBUG1(fmt,a) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), (a))
+#define DEBUG2(fmt,a,b) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), (a), (b))
+#define DEBUG3(fmt,a,b,c) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), (a), (b), \
+		(c))
+#define DEBUG4(fmt,a,b,c,d) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), (a), (b), \
+		(c), (d))
+#define DEBUG5(fmt,a,b,c,d,e) \
+  _gpgme_debug (1, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__), (a), (b), \
+		(c), (d), (e))
+#define DEBUG_BEGIN(hlp,lvl,fmt) \
+  _gpgme_debug_begin (&(hlp), lvl, "%s:%s: " fmt, __FILE__, XSTRINGIFY (__LINE__))
+#define DEBUG_ADD0(hlp,fmt) \
+  _gpgme_debug_add (&(hlp), fmt)
+#define DEBUG_ADD1(hlp,fmt,a) \
+  _gpgme_debug_add (&(hlp), fmt, (a))
+#define DEBUG_ADD2(hlp,fmt,a,b) \
+  _gpgme_debug_add (&(hlp), fmt, (a), (b))
+#define DEBUG_ADD3(hlp,fmt,a,b,c) \
+  _gpgme_debug_add (&(hlp), fmt, (a), (b), (c))
+#define DEBUG_END(hlp,fmt) \
+  _gpgme_debug_add (&(hlp), fmt); \
+  _gpgme_debug_end (&(hlp))
+#endif
+
+#define DEBUG_ENABLED(hlp) (!!(hlp))
+
+#endif	/* DEBUG_H */