commit 4b3be6afa4ab8b3fdce39df68bad71f8b85164de
author Julia Lawall <julia@diku.dk> Sat Oct 17 08:33:22 2009 +0200
committer Takashi Iwai <tiwai@suse.de> Fri Oct 30 12:01:27 2009 +0100
tree 9022bd2b563fabc987e31277782076db42946bb7
parent b71207e9dc044b30d8b5d7f1c2290ba14563f05c

ALSA: sound: Move dereference after NULL test and drop unnecessary NULL tests

In pcm.c, if the NULL test on pcm is needed, then the dereference should be
after the NULL test.

In dummy.c and ali5451.c, the context of the calls to
snd_card_dummy_new_mixer and snd_ali_free_voice show that dummy and pvoice,
respectively cannot be NULL.

A simplified version of the semantic match that detects this problem is as
follows (http://coccinelle.lip6.fr/):

// <smpl>
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm.c

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 0c14401..c69c60b 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -953,11 +953,12 @@
 	struct snd_pcm_substream *substream;
 	struct snd_pcm_notify *notify;
 	char str[16];
-	struct snd_pcm *pcm = device->device_data;
+	struct snd_pcm *pcm;
 	struct device *dev;
 
-	if (snd_BUG_ON(!pcm || !device))
+	if (snd_BUG_ON(!device || !device->device_data))
 		return -ENXIO;
+	pcm = device->device_data;
 	mutex_lock(&register_mutex);
 	err = snd_pcm_add(pcm);
 	if (err) {

sound/drivers/dummy.c

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index 6ba066c..146ef00 100644
--- a/sound/drivers/dummy.c
+++ b/sound/drivers/dummy.c
@@ -808,8 +808,6 @@
 	unsigned int idx;
 	int err;
 
-	if (snd_BUG_ON(!dummy))
-		return -EINVAL;
 	spin_lock_init(&dummy->mixer_lock);
 	strcpy(card->mixername, "Dummy Mixer");
 

sound/pci/ali5451/ali5451.c

diff --git a/sound/pci/ali5451/ali5451.c b/sound/pci/ali5451/ali5451.c
index b458d20..aaf4da6 100644
--- a/sound/pci/ali5451/ali5451.c
+++ b/sound/pci/ali5451/ali5451.c
@@ -973,7 +973,7 @@
 	void *private_data;
 
 	snd_ali_printk("free_voice: channel=%d\n",pvoice->number);
-	if (pvoice == NULL || !pvoice->use)
+	if (!pvoice->use)
 		return;
 	snd_ali_clear_voices(codec, pvoice->number, pvoice->number);
 	spin_lock_irq(&codec->voice_alloc);