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options: simplify mp_get_config_group() memory management 

There is some craziness here: the function allocates m_config_cache,
which in turn allocates the actual option struct, which is what the
function returns. The user would expect to be able to use talloc_free()
to deallocate everything. Of course this didn't work, because the
returned pointer is not the root parent in the talloc tree.

But with some additional talloc craziness, this can be fixed. We
rearrange the parent pointers such that freeing the option struct will
free m_config_cache first, which uninits the contents in the option
struct, but fortunately not the option struct itself.

This change should simplify API use on the caller side, and reduce
surprises.
This commit is contained in:
wm4 2018-01-16 11:35:37 +01:00 committed by Kevin Mitchell
parent cc3cdcb0f0
commit 1d3b680427
2 changed files with 4 additions and 4 deletions
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6
options/m_config.c
View File

@ -1437,8 +1437,10 @@ bool m_config_is_in_group(struct m_config *config,
void *mp_get_config_group(void *ta_parent, struct mpv_global *global,
const struct m_sub_options *group)
{
assert(ta_parent); // without you'd necessarily leak memory
struct m_config_cache *cache = m_config_cache_alloc(ta_parent, global, group);
struct m_config_cache *cache = m_config_cache_alloc(NULL, global, group);
// Make talloc_free(cache->opts) free the entire cache.
ta_set_parent(cache->opts, ta_parent);
ta_set_parent(cache, cache->opts);
return cache->opts;
}

2
options/m_config.h
View File

@ -325,8 +325,6 @@ bool m_config_cache_update(struct m_config_cache *cache);
// Like m_config_cache_alloc(), but return the struct (m_config_cache->opts)
// directly, with no way to update the config. Basically this returns a copy
// with a snapshot of the current option values.
// Warning: does currently not set the child as its own talloc root, which
// means the only way to free the struct is by freeing ta_parent.
void *mp_get_config_group(void *ta_parent, struct mpv_global *global,
const struct m_sub_options *group);