[libvirt] [PATCH] let gcc's -Wformat do its job; avoid "make syntax-check" failure

[Jim Meyering <jim@xxxxxxxxxxxx>]

I first noticed that "make syntax-check" failed.
Then I saw that virAsprintf's prototype lacked ATTRIBUTE_FORMAT.
This fixes both and updates HACKING.


>From 5bae37c505738ed4223625f8e3cc88ad6f4bf68c Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@xxxxxxxxxx>
Date: Wed, 17 Dec 2008 08:54:46 +0100
Subject: [PATCH] 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.
---
 HACKING    |   16 ++++++++++++++++
 src/util.c |    2 +-
 src/util.h |    3 ++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/HACKING b/HACKING
index 3945833..e088da8 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 12097d4..9eda378 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 3d603dc..0475bd3 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
--
1.6.1.rc2.316.geb2f0

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