coding-style: add rule about checking NULL pointer

1 files changed, 21 insertions, 0 deletions

diff --git a/doc/coding-style.txt b/doc/coding-style.txt
index eccdacc6..9dfdc09c 100644
--- a/doc/coding-style.txt
+++ b/doc/coding-style.txt
@@ -209,6 +209,27 @@ However if the enum comes from an external header file outside ofono
 we cannot make any assumption of how the enum is defined and this
 rule might not apply.
 
+M13: Check for pointer being NULL
+=================================
+
+When checking if a pointer or a return value is NULL, explicitly compare to
+NULL rather than use the shorter check with "!" operator.
+
+Example:
+1)
+array = g_try_new0(int, 20);
+if (!array)	// Wrong
+	return;
+
+2)
+if (!g_at_chat_get_slave(chat))	// Wrong
+	return -EINVAL;
+
+3)
+array = g_try_new0(int, 20);
+if (array == NULL)	// Correct
+	return;
+
 O1: Shorten the name
 ====================
 Better to use abbreviation, rather than full name, to name a variable,