diff --git a/ChangeLog b/ChangeLog
index 5ca5dec74b..323120d911 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Dec 17 18:10:51 +0100 2008 Jim Meyering <meyering@redhat.com>
+
+	let gcc's -Wformat do its job; avoid "make syntax-check" failure
+	* src/util.c (virAsprintf): Remove trailing space.
+	* src/util.h (virAsprintf): Use ATTRIBUTE_FORMAT.
+	* HACKING (Printf-style functions): New section.
+
 Wed Dec 17 16:43:39 GMT 2008 Daniel P. Berrange <berrange@redhat.com>
 
 	* src/libvirt.c: Add missing checks for read-only connection
diff --git a/HACKING b/HACKING
index 3945833f29..e088da8628 100644
--- a/HACKING
+++ b/HACKING
@@ -247,6 +247,22 @@ are some special reasons why you cannot include these files
 explicitly.
 
 
+Printf-style functions
+======================
+
+Whenever you add a new printf-style function, i.e., one with a format
+string argument and following "..." in its prototype, be sure to use
+gcc's printf attribute directive in the prototype.  For example, here's
+the one for virAsprintf, in util.h:
+
+    int virAsprintf(char **strp, const char *fmt, ...)
+	ATTRIBUTE_FORMAT(printf, 2, 3);
+
+This makes it so gcc's -Wformat and -Wformat-security options can do
+their jobs and cross-check format strings with the number and types
+of arguments.
+
+
 
                 Libvirt commiters guidelines
                 ============================
diff --git a/src/util.c b/src/util.c
index 12097d41aa..9eda378509 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1158,7 +1158,7 @@ virParseNumber(const char **str)
  *
  * like asprintf but makes sure *strp == NULL on failure
  */
-int 
+int
 virAsprintf(char **strp, const char *fmt, ...)
 {
     va_list ap;
diff --git a/src/util.h b/src/util.h
index 3d603dc531..0475bd3569 100644
--- a/src/util.h
+++ b/src/util.h
@@ -112,7 +112,8 @@ int virMacAddrCompare (const char *mac1, const char *mac2);
 
 void virSkipSpaces(const char **str);
 int virParseNumber(const char **str);
-int virAsprintf(char **strp, const char *fmt, ...);
+int virAsprintf(char **strp, const char *fmt, ...)
+    ATTRIBUTE_FORMAT(printf, 2, 3);
 
 #define VIR_MAC_BUFLEN 6
 #define VIR_MAC_PREFIX_BUFLEN 3