various: correctly ignore cache files with --no-config

--no-config should prevent loading user files of any type: configs,
cache, etc. For cache files, this case wasn't properly handled and it
was assumed they would always get something. vo_gpu's shader cache
actually already handles this, so it was left untouched. In theory,
demuxer cache should never have this issue because saving it to disk is
disabled by default (and likely that will never change), but go ahead
and change it for consistency's sake. Fixes some segfaults with
--no-config and various combinations of settings (particularly
--vo=gpu-next).

DOCS/man/options.rst

@@ -719,9 +719,9 @@ Program Behavior
     Print version string and exit.
 
 ``--no-config``
-    Do not load default configuration files. This prevents loading of both the
-    user-level and system-wide ``mpv.conf`` and ``input.conf`` files. Other
-    configuration files are blocked as well, such as resume playback files.
+    Do not load default configuration or any user files. This prevents loading of
+    both the user-level and system-wide ``mpv.conf`` and ``input.conf`` files. Other
+    user files are blocked as well, such as resume playback files and cache files.
 
     .. note::
 

demux/cache.c

@@ -105,8 +105,11 @@ struct demux_cache *demux_cache_create(struct mpv_global *global,
     } else {
         cache_dir = mp_find_user_file(NULL, global, "cache", "");
     }
-    mp_mkdirp(cache_dir);
 
+    if (!cache_dir || !cache_dir[0])
+        goto fail;
+
+    mp_mkdirp(cache_dir);
     cache->filename = mp_path_join(cache, cache_dir, "mpv-cache-XXXXXX.dat");
     cache->fd = mp_mkostemps(cache->filename, 4, O_CLOEXEC);
     if (cache->fd < 0) {

video/out/gpu/lcms.c

@@ -359,12 +359,13 @@ bool gl_lcms_get_lut3d(struct gl_lcms *p, struct lut3d **result_lut3d,
             cache_dir = mp_find_user_file(tmp, p->global, "cache", "");
         }
 
-        cache_file = talloc_strdup(tmp, "");
-        for (int i = 0; i < sizeof(hash); i++)
-            cache_file = talloc_asprintf_append(cache_file, "%02X", hash[i]);
-        cache_file = mp_path_join(tmp, cache_dir, cache_file);
-
-        mp_mkdirp(cache_dir);
+        if (cache_dir && cache_dir[0]) {
+            cache_file = talloc_strdup(tmp, "");
+            for (int i = 0; i < sizeof(hash); i++)
+                cache_file = talloc_asprintf_append(cache_file, "%02X", hash[i]);
+            cache_file = mp_path_join(tmp, cache_dir, cache_file);
+            mp_mkdirp(cache_dir);
+        }
     }
 
     // check cache

video/out/vo_gpu_next.c

@@ -1381,9 +1381,10 @@ static void wait_events(struct vo *vo, int64_t until_time_us)
 
 static char *get_cache_file(struct priv *p)
 {
+    char *file = NULL;
     struct gl_video_opts *opts = p->opts_cache->opts;
     if (!opts->shader_cache)
-        return NULL;
+        goto done;
 
     char *dir = opts->shader_cache_dir;
     if (dir && dir[0]) {
@@ -1391,9 +1392,12 @@ static char *get_cache_file(struct priv *p)
     } else {
         dir = mp_find_user_file(NULL, p->global, "cache", "");
     }
-    char *file = mp_path_join(NULL, dir, "libplacebo.cache");
-    mp_mkdirp(dir);
+    if (dir && dir[0]) {
+        file = mp_path_join(NULL, dir, "libplacebo.cache");
+        mp_mkdirp(dir);
+    }
     talloc_free(dir);
+done:
     return file;
 }
 
@@ -1635,8 +1639,11 @@ static stream_t *icc_open_cache(struct priv *p, uint64_t sig, int flags)
     } else {
         cache_dir = mp_find_user_file(NULL, p->global, "cache", "");
     }
-    char *path = mp_path_join(NULL, cache_dir, cache_name);
 
+    if (!cache_dir || !cache_dir[0])
+        return NULL;
+
+    char *path = mp_path_join(NULL, cache_dir, cache_name);
     stream_t *stream = NULL;
     if (flags & STREAM_WRITE) {
         mp_mkdirp(cache_dir);