[alsa-devel] [PATCH 16/34] pcm: remove alloca() from snd_pcm_hw_set_chmap()

[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_hw.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index 20c233b..3a5634c 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -1261,8 +1261,8 @@ static int snd_pcm_hw_set_chmap(snd_pcm_t *pcm, const snd_pcm_chmap_t *map)
 {
 	snd_pcm_hw_t *hw = pcm->private_data;
 	snd_ctl_t *ctl;
-	snd_ctl_elem_id_t *id;
-	snd_ctl_elem_value_t *val;
+	snd_ctl_elem_id_t id = {0};
+	snd_ctl_elem_value_t val = {0};
 	unsigned int i;
 	int ret;
 
@@ -1287,13 +1287,12 @@ static int snd_pcm_hw_set_chmap(snd_pcm_t *pcm, const snd_pcm_chmap_t *map)
 		chmap_caps_set_error(hw, CHMAP_CTL_SET);
 		return ret;
 	}
-	snd_ctl_elem_id_alloca(&id);
-	snd_ctl_elem_value_alloca(&val);
-	fill_chmap_ctl_id(pcm, id);
-	snd_ctl_elem_value_set_id(val, id);
+
+	fill_chmap_ctl_id(pcm, &id);
+	snd_ctl_elem_value_set_id(&val, &id);
 	for (i = 0; i < map->channels; i++)
-		snd_ctl_elem_value_set_integer(val, i, map->pos[i]);
-	ret = snd_ctl_elem_write(ctl, val);
+		snd_ctl_elem_value_set_integer(&val, i, map->pos[i]);
+	ret = snd_ctl_elem_write(ctl, &val);
 	snd_ctl_close(ctl);
 	if (ret >= 0)
 		chmap_caps_set_ok(hw, CHMAP_CTL_SET);
-- 
2.7.4