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Commit d5702162 authored by Christine Spang's avatar Christine Spang Committed by Takashi Iwai
Browse files

ALSA: Make snd_BUG_ON() always evaluate and return the conditional expression 



Having snd_BUG_ON() only evaluate its conditional when CONFIG_SND_DEBUG
is set leads to frequent bugs, since other similar macros in the kernel
have different behavior. Let's make snd_BUG_ON() act like those macros
so it will stop being accidentally misused.

Signed-off-by: default avatarChristine Spang <christine.spang@oracle.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 8ba955ce

Documentation/DocBook/writing-an-alsa-driver.tmpl

+5 −7
Original line number Diff line number Diff line
@@ -6164,14 +6164,12 @@ struct _snd_pcm_runtime { 


      <para>

        The macro takes an conditional expression to evaluate.

	When <constant>CONFIG_SND_DEBUG</constant>, is set, the

	expression is actually evaluated. If it's non-zero, it shows

	the warning message such as

	When <constant>CONFIG_SND_DEBUG</constant>, is set, if the

	expression is non-zero, it shows the warning message such as

	<computeroutput>BUG? (xxx)</computeroutput>

	normally followed by stack trace.  It returns the evaluated

	value.

	When no <constant>CONFIG_SND_DEBUG</constant> is set, this

	macro always returns zero.

	normally followed by stack trace.



	In both cases it returns the evaluated value.

      </para>



    </section>

include/sound/core.h

+8 −16
Original line number Diff line number Diff line
@@ -379,18 +379,10 @@ void __snd_printk(unsigned int level, const char *file, int line, 
 * snd_BUG_ON - debugging check macro

 * @cond: condition to evaluate

 *

 * When CONFIG_SND_DEBUG is set, this macro evaluates the given condition,

 * and call WARN() and returns the value if it's non-zero.

 * 

 * When CONFIG_SND_DEBUG is not set, this just returns zero, and the given

 * condition is ignored.

 *

 * NOTE: the argument won't be evaluated at all when CONFIG_SND_DEBUG=n.

 * Thus, don't put any statement that influences on the code behavior,

 * such as pre/post increment, to the argument of this macro.

 * If you want to evaluate and give a warning, use standard WARN_ON().

 * Has the same behavior as WARN_ON when CONFIG_SND_DEBUG is set,

 * otherwise just evaluates the conditional and returns the value.

 */

#define snd_BUG_ON(cond)	WARN((cond), "BUG? (%s)\n", __stringify(cond))

#define snd_BUG_ON(cond)	WARN_ON((cond))



#else /* !CONFIG_SND_DEBUG */
@@ -400,11 +392,11 @@ __printf(2, 3) 
static inline void _snd_printd(int level, const char *format, ...) {}



#define snd_BUG()			do { } while (0)

static inline int __snd_bug_on(int cond)

{

	return 0;

}

#define snd_BUG_ON(cond)	__snd_bug_on(0 && (cond))  /* always false */



#define snd_BUG_ON(condition) ({ \

	int __ret_warn_on = !!(condition); \

	unlikely(__ret_warn_on); \

})



#endif /* CONFIG_SND_DEBUG */