audio: make mp_chmap_to_str() return a stack-allocated string

Simplifies memory management.

audio/audio.c

@@ -93,10 +93,9 @@ bool mp_audio_config_valid(const struct mp_audio *mpa)
 
 char *mp_audio_fmt_to_str(int srate, const struct mp_chmap *chmap, int format)
 {
-    char *chstr = mp_chmap_to_str(chmap);
-    char *res = talloc_asprintf(NULL, "%dHz %s %dch %s", srate, chstr,
-                                chmap->num, af_fmt_to_str(format));
-    talloc_free(chstr);
+    char *res = talloc_asprintf(NULL, "%dHz %s %dch %s", srate,
+                                mp_chmap_to_str(chmap), chmap->num,
+                                af_fmt_to_str(format));
     return res;
 }
 

audio/chmap.c

@@ -18,6 +18,7 @@
 #include <stdlib.h>
 #include <assert.h>
 
+#include "common/common.h"
 #include "common/msg.h"
 #include "chmap.h"
 
@@ -376,34 +377,35 @@ void mp_chmap_get_reorder(int dst[MP_NUM_CHANNELS], const struct mp_chmap *from,
 // Returns something like "fl-fr-fc". If there's a standard layout in lavc
 // order, return that, e.g. "3.0" instead of "fl-fr-fc".
 // Unassigned but valid speakers get names like "sp28".
-char *mp_chmap_to_str(const struct mp_chmap *src)
+char *mp_chmap_to_str_buf(char *buf, size_t buf_size, const struct mp_chmap *src)
 {
-    char *res = talloc_strdup(NULL, "");
+    buf[0] = '\0';
 
-    if (mp_chmap_is_unknown(src))
-        return talloc_asprintf_append_buffer(res, "unknown%d", src->num);
+    if (mp_chmap_is_unknown(src)) {
+        snprintf(buf, buf_size, "unknown%d", src->num);
+        return buf;
+    }
 
     for (int n = 0; n < src->num; n++) {
         int sp = src->speaker[n];
         const char *s = sp < MP_SPEAKER_ID_COUNT ? speaker_names[sp][0] : NULL;
-        char buf[10];
+        char sp_buf[10];
         if (!s) {
-            snprintf(buf, sizeof(buf), "sp%d", sp);
-            s = buf;
+            snprintf(sp_buf, sizeof(sp_buf), "sp%d", sp);
+            s = sp_buf;
         }
-        res = talloc_asprintf_append_buffer(res, "%s%s", n > 0 ? "-" : "", s);
+        mp_snprintf_cat(buf, buf_size, "%s%s", n > 0 ? "-" : "", s);
     }
 
     // To standard layout name
     for (int n = 0; std_layout_names[n][0]; n++) {
-        if (res && strcmp(res, std_layout_names[n][1]) == 0) {
-            talloc_free(res);
-            res = talloc_strdup(NULL, std_layout_names[n][0]);
+        if (strcmp(buf, std_layout_names[n][1]) == 0) {
+            snprintf(buf, buf_size, "%s", std_layout_names[n][0]);
             break;
         }
     }
 
-    return res;
+    return buf;
 }
 
 // If src can be parsed as channel map (as produced by mp_chmap_to_str()),

audio/chmap.h

@@ -120,7 +120,9 @@ void mp_chmap_reorder_to_lavc(struct mp_chmap *map);
 void mp_chmap_get_reorder(int dst[MP_NUM_CHANNELS], const struct mp_chmap *from,
                           const struct mp_chmap *to);
 
-char *mp_chmap_to_str(const struct mp_chmap *src);
+char *mp_chmap_to_str_buf(char *buf, size_t buf_size, const struct mp_chmap *src);
+#define mp_chmap_to_str(m) mp_chmap_to_str_buf((char[64]){0}, 64, (m))
+
 bool mp_chmap_from_str(struct mp_chmap *dst, bstr src);
 
 struct mp_log;

audio/out/ao.c

@@ -214,10 +214,9 @@ static struct ao *ao_alloc_pb(bool probing, struct mpv_global *global,
 
 static int ao_init(struct ao *ao)
 {
-    char *chmap = mp_chmap_to_str(&ao->channels);
     MP_VERBOSE(ao, "requested format: %d Hz, %s channels, %s\n",
-               ao->samplerate, chmap, af_fmt_to_str(ao->format));
-    talloc_free(chmap);
+               ao->samplerate, mp_chmap_to_str(&ao->channels),
+               af_fmt_to_str(ao->format));
 
     ao->api = ao->driver->play ? &ao_api_push : &ao_api_pull;
     ao->api_priv = talloc_zero_size(ao, ao->api->priv_size);

audio/out/ao_alsa.c

@@ -317,10 +317,8 @@ static const char *select_chmap(struct ao *ao)
             return device_channel_layouts[n][0];
     }
 
-    char *name = mp_chmap_to_str(&ao->channels);
     MP_ERR(ao, "channel layout %s (%d ch) not supported.\n",
-           name, ao->channels.num);
-    talloc_free(name);
+           mp_chmap_to_str(&ao->channels), ao->channels.num);
     return "default";
 }
 
@@ -587,9 +585,7 @@ static int init(struct ao *ao)
         for (int c = 0; c < chmap.num; c++)
             chmap.speaker[c] = find_mp_channel(alsa_chmap->pos[c]);
 
-        char *mp_map_str = mp_chmap_to_str(&chmap);
-        MP_VERBOSE(ao, "which we understand as: %s\n", mp_map_str);
-        talloc_free(mp_map_str);
+        MP_VERBOSE(ao, "which we understand as: %s\n", mp_chmap_to_str(&chmap));
 
         if (mp_chmap_is_valid(&chmap) && chmap.num == ao->channels.num) {
             MP_VERBOSE(ao, "using the ALSA channel map.\n");

player/command.c

@@ -1571,7 +1571,7 @@ static int mp_property_channels(void *ctx, struct m_property *prop,
         return M_PROPERTY_UNAVAILABLE;
     switch (action) {
     case M_PROPERTY_PRINT:
-        *(char **) arg = mp_chmap_to_str(&fmt.channels);
+        *(char **) arg = talloc_strdup(NULL, mp_chmap_to_str(&fmt.channels));
         return M_PROPERTY_OK;
     case M_PROPERTY_GET:
         *(int *)arg = fmt.channels.num;