util: Add abort_with_msg() and ASSERT_WITH_MSG() helpers

We already have the ASSERT() macro which will abort() passt based on a
condition.  It always has a fixed error message based on its location and
the asserted expression.  We have some upcoming cases where we want to
customise the message when hitting an assert.

Add abort_with_msg() and ASSERT_WITH_MSG() helpers to allow this.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

util.c

@@ -1017,3 +1017,22 @@ void encode_domain_name(char *buf, const char *domain_name)
 	}
 	p[i] = 0L;
 }
+
+/**
+ * abort_with_msg() - Print error message and abort
+ * @fmt:	Format string
+ * @...:	Format parameters
+ */
+void abort_with_msg(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vlogmsg(true, false, LOG_CRIT, fmt, ap);
+	va_end(ap);
+
+	/* This may actually cause a SIGSYS instead of SIGABRT, due to seccomp,
+	 * but that will still get the job done.
+	 */
+	abort();
+}

util.h

@@ -61,27 +61,22 @@
 #define STRINGIFY(x)	#x
 #define STR(x)		STRINGIFY(x)
 
-#ifdef CPPCHECK_6936
+void abort_with_msg(const char *fmt, ...)
+	__attribute__((format(printf, 1, 2), noreturn));
+
 /* Some cppcheck versions get confused by aborts inside a loop, causing
  * it to give false positive uninitialised variable warnings later in
  * the function, because it doesn't realise the non-initialising path
  * already exited.  See https://trac.cppcheck.net/ticket/13227
+ *
+ * Therefore, avoid using the usual do while wrapper we use to force the macro
+ * to act like a single statement requiring a ';'.
  */
-#define ASSERT(expr)		\
-	((expr) ? (void)0 : abort())
-#else
+#define ASSERT_WITH_MSG(expr, ...)					\
+	((expr) ? (void)0 : abort_with_msg(__VA_ARGS__))
 #define ASSERT(expr)							\
-	do {								\
-		if (!(expr)) {						\
-			err("ASSERTION FAILED in %s (%s:%d): %s",	\
-			    __func__, __FILE__, __LINE__, STRINGIFY(expr)); \
-			/* This may actually SIGSYS, due to seccomp,	\
-			 * but that will still get the job done		\
-			 */						\
-			abort();					\
-		}							\
-	} while (0)
-#endif
+	ASSERT_WITH_MSG((expr), "ASSSERTION FAILED in %s (%s:%d): %s",	\
+			__func__, __FILE__, __LINE__, STRINGIFY(expr))
 
 #ifdef P_tmpdir
 #define TMPDIR		P_tmpdir