[alsa-devel] [PATCH 20/34] pcm: remove alloca() from softvol_load_control()

[Takashi Sakamoto]

Both of alloca() and automatic variables keeps storages on stack, while
the former generates more instructions than the latter. It's better to use
the latter if the size of storage is computable at pre-compile or compile
time; i.e. just for structures.

This commit obsolete usages of alloca() with automatic variables.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 src/pcm/pcm_softvol.c | 38 ++++++++++++++++++--------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/src/pcm/pcm_softvol.c b/src/pcm/pcm_softvol.c
index 4d2c62a..fc45d6d 100644
--- a/src/pcm/pcm_softvol.c
+++ b/src/pcm/pcm_softvol.c
@@ -702,17 +702,16 @@ static int softvol_load_control(snd_pcm_t *pcm, snd_pcm_softvol_t *svol,
 				int resolution)
 {
 	char tmp_name[32];
-	snd_pcm_info_t *info;
-	snd_ctl_elem_info_t *cinfo;
+	snd_pcm_info_t info = {0};
+	snd_ctl_elem_info_t cinfo = {0};
 	int err;
 	unsigned int i;
 
 	if (ctl_card < 0) {
-		snd_pcm_info_alloca(&info);
-		err = snd_pcm_info(pcm, info);
+		err = snd_pcm_info(pcm, &info);
 		if (err < 0)
 			return err;
-		ctl_card = snd_pcm_info_get_card(info);
+		ctl_card = snd_pcm_info_get_card(&info);
 		if (ctl_card < 0) {
 			SNDERR("No card defined for softvol control");
 			return -EINVAL;
@@ -737,46 +736,45 @@ static int softvol_load_control(snd_pcm_t *pcm, snd_pcm_softvol_t *svol,
 		svol->zero_dB_val = (min_dB / (min_dB - max_dB)) *
 								svol->max_val;
 		
-	snd_ctl_elem_info_alloca(&cinfo);
-	snd_ctl_elem_info_set_id(cinfo, ctl_id);
-	if ((err = snd_ctl_elem_info(svol->ctl, cinfo)) < 0) {
+	snd_ctl_elem_info_set_id(&cinfo, ctl_id);
+	if ((err = snd_ctl_elem_info(svol->ctl, &cinfo)) < 0) {
 		if (err != -ENOENT) {
 			SNDERR("Cannot get info for CTL %s", tmp_name);
 			return err;
 		}
-		err = add_user_ctl(svol, cinfo, cchannels);
+		err = add_user_ctl(svol, &cinfo, cchannels);
 		if (err < 0) {
 			SNDERR("Cannot add a control");
 			return err;
 		}
 	} else {
-		if (! (cinfo->access & SNDRV_CTL_ELEM_ACCESS_USER)) {
+		if (! (cinfo.access & SNDRV_CTL_ELEM_ACCESS_USER)) {
 			/* hardware control exists */
 			return 1; /* notify */
 
-		} else if ((cinfo->type != SND_CTL_ELEM_TYPE_INTEGER &&
-			    cinfo->type != SND_CTL_ELEM_TYPE_BOOLEAN) ||
-			   cinfo->count != (unsigned int)cchannels ||
-			   cinfo->value.integer.min != 0 ||
-			   cinfo->value.integer.max != resolution - 1) {
-			err = snd_ctl_elem_remove(svol->ctl, &cinfo->id);
+		} else if ((cinfo.type != SND_CTL_ELEM_TYPE_INTEGER &&
+			    cinfo.type != SND_CTL_ELEM_TYPE_BOOLEAN) ||
+			   cinfo.count != (unsigned int)cchannels ||
+			   cinfo.value.integer.min != 0 ||
+			   cinfo.value.integer.max != resolution - 1) {
+			err = snd_ctl_elem_remove(svol->ctl, &cinfo.id);
 			if (err < 0) {
 				SNDERR("Control %s mismatch", tmp_name);
 				return err;
 			}
 			/* reset numid */
-			snd_ctl_elem_info_set_id(cinfo, ctl_id);
-			if ((err = add_user_ctl(svol, cinfo, cchannels)) < 0) {
+			snd_ctl_elem_info_set_id(&cinfo, ctl_id);
+			if ((err = add_user_ctl(svol, &cinfo, cchannels)) < 0) {
 				SNDERR("Cannot add a control");
 				return err;
 			}
 		} else if (svol->max_val > 1) {
 			/* check TLV availability */
 			unsigned int tlv[4];
-			err = snd_ctl_elem_tlv_read(svol->ctl, &cinfo->id, tlv,
+			err = snd_ctl_elem_tlv_read(svol->ctl, &cinfo.id, tlv,
 						    sizeof(tlv));
 			if (err < 0)
-				add_tlv_info(svol, cinfo);
+				add_tlv_info(svol, &cinfo);
 		}
 	}
 
-- 
2.7.4