audio: allow more than 20 channel map entries

This could trigger an assertion when using ao_alsa or ao_coreaudio. The
code was simply assuming the number of channel maps was bounded
statically (which was true at first in both AOs).

Fix by using dynamic memory allocation. It needs to be explicitly
enabled by the AOs by setting a temp context, because otherwise the
memory couldn't be freed. (Or at least this seems to be the most elegant
solution.)

Fixes #1306.

4 files changed, 19 insertions, 8 deletions

diff --git a/audio/chmap_sel.c b/audio/chmap_sel.c
index 160f1ce5fa..8e591aea44 100644
--- a/audio/chmap_sel.c
+++ b/audio/chmap_sel.c
@@ -81,14 +81,21 @@ void mp_chmap_sel_add_alsa_def(struct mp_chmap_sel *s)
     }
 }
 
-#define ARRAY_LEN(x) (sizeof(x) / sizeof((x)[0]))
-
 // Add a channel map that should be allowed.
 void mp_chmap_sel_add_map(struct mp_chmap_sel *s, const struct mp_chmap *map)
 {
-    assert(s->num_chmaps < ARRAY_LEN(s->chmaps));
-    if (mp_chmap_is_valid(map))
-        s->chmaps[s->num_chmaps++] = *map;
+    if (!mp_chmap_is_valid(map))
+        return;
+    if (!s->chmaps)
+        s->chmaps = s->chmaps_storage;
+    if (s->num_chmaps == MP_ARRAY_SIZE(s->chmaps)) {
+        if (!s->tmp)
+            return;
+        s->chmaps = talloc_memdup(s->tmp, s->chmaps, sizeof(s->chmaps_storage));
+    }
+    if (s->chmaps != s->chmaps_storage)
+        MP_TARRAY_GROW(s->tmp, s->chmaps, s->num_chmaps);
+    s->chmaps[s->num_chmaps++] = *map;
 }
 
 // Allow all waveext formats in default order.
diff --git a/audio/chmap_sel.h b/audio/chmap_sel.h
index c9d75196a5..7758ca5d74 100644
--- a/audio/chmap_sel.h
+++ b/audio/chmap_sel.h
@@ -26,8 +26,12 @@ struct mp_chmap_sel {
     // should be considered opaque
     bool allow_any, allow_waveext;
     bool speakers[MP_SPEAKER_ID_COUNT];
-    struct mp_chmap chmaps[20];
+    struct mp_chmap *chmaps;
     int num_chmaps;
+
+    struct mp_chmap chmaps_storage[20];
+
+    void *tmp; // set to any talloc context to allow more chmaps entries
 };
 
 void mp_chmap_sel_add_any(struct mp_chmap_sel *s);
diff --git a/audio/out/ao_alsa.c b/audio/out/ao_alsa.c
index 86745c6e80..4e54f161fe 100644
--- a/audio/out/ao_alsa.c
+++ b/audio/out/ao_alsa.c
@@ -279,7 +279,7 @@ static int find_alsa_channel(int mp_channel)
 static bool query_chmaps(struct ao *ao, struct mp_chmap *chmap)
 {
     struct priv *p = ao->priv;
-    struct mp_chmap_sel chmap_sel = {0};
+    struct mp_chmap_sel chmap_sel = {.tmp = p};
 
     snd_pcm_chmap_query_t **maps = snd_pcm_query_chmaps(p->alsa);
     if (!maps)
diff --git a/audio/out/ao_coreaudio.c b/audio/out/ao_coreaudio.c
index 1e1ad8cb10..6498f3ecad 100644
--- a/audio/out/ao_coreaudio.c
+++ b/audio/out/ao_coreaudio.c
@@ -185,7 +185,7 @@ static bool init_chmap(struct ao *ao)
                        &layouts, &n_layouts);
     CHECK_CA_ERROR("could not get audio device prefered layouts");
 
-    struct mp_chmap_sel chmap_sel = {0};
+    struct mp_chmap_sel chmap_sel = {.tmp = p};
     for (int i = 0; i < n_layouts; i++) {
         struct mp_chmap chmap = {0};
         if (ca_layout_to_mp_chmap(ao, &layouts[i], &chmap))