Up until now, `spa/utils/cleanup.h` was not installed,
but 779f06865c ("pod: add spa_auto support for dynamic builder")
included it in a public header. So now `cleanup.h` also needs to
be installed like any other public header so as to not break
3rd party users.
For example, `xdg-desktop-portal-wlr` would break:
https://codesearch.debian.net/search?q=spa_pod_dynamic_builder_init&literal=1
systemd, dbus-broker, and many glib applications heavily
utilize the GNU C attribute "cleanup" to achieve C++ RAII-like
semantics for local resource management. This commit introduces
essentialy same mechanism into pipewire.
At the moment, this is inteded to be a strictly private API.
free() and close() as cleanup targets are sufficiently common
to warrant their own special macros:
spa_autofree char *s = strdup(p);
// will call `free(s)` at the end of the lifetime of `s`
spa_autoclose int fd = openat(...);
// will call `close(fd)` if `fd >= 0` at the end of the lifetime of `fd`
However, with `spa_auto()` or `spa_autoptr()` it is possible to define
other variables that will be cleaned up properly. Currently four are supported:
spa_autoptr(FILE) f = fopen(...);
// `f` has type `FILE *`
// will call `fclose(f)` if `f != NULL`
spa_autoptr(DIR) d = opendir(...);
// `d` has type `DIR *`
// will call `closedir(d)` if `d != NULL`
spa_autoptr(pw_properties) p = pw_properties_new(NULL, NULL);
// `p` has type `struct pw_properties *`
// will call `pw_properties_free(p)`
spa_auto(pw_strv) v = pw_split_strv(...);
// `v` has type `char **`
// will call `pw_strv_free(v)`
It is possible to add support for other types, e.g.
SPA_DEFINE_AUTOPTR_CLEANUP(pw_main_loop, struct pw_main_loop, {
// the pointer can be accessed using `*thing`
// `thing` has type `struct pw_main_loop **`
spa_clear_ptr(*thing, pw_main_loop_destroy);
})
spa_autoptr(pw_main_loop) l = ...;
// `l` has type `struct pw_main_loop *`
// will call `pw_main_loop_destroy(l)`
or
SPA_DEFINE_AUTO_CLEANUP(spa_pod_dynamic_builder, struct spa_pod_dynamic_builder, {
// `thing` has type `struct spa_pod_dynamic_builder *`
spa_pod_dynamic_builder_clean(thing);
})
spa_auto(spa_pod_dynamic_builder) builder = ...
// `builder` has type `struct spa_pod_dynamic_builder`
// will call `spa_pod_dynamic_builder_clean(&builder)`
The first argument is always an arbitrary name. This name must be passed to
`spa_auto()` and `spa_autoptr()` as it is what determines the actual type
and destructor used. The second parameter is the concrete type. For
`SPA_DEFINE_AUTO_CLEANUP()` this is the concrete type to be used, while for
`SPA_DEFINE_AUTOPTR_CLEANUP()` it is the concrete type without the
outermost pointer. That is,
SPA_DEFINE_AUTOPTR_CLEANUP(A, foo, ...)
SPA_DEFINE_AUTO_CLEANUP(B, foo, ...)
spa_autoptr(A) x; // `x` has type `foo *`
spa_auto(B) y; // `y` has type `foo`
A couple other macros are also added:
spa_clear_ptr(ptr, destructor)
// calls `destructor(ptr)` if `ptr != NULL` and sets `ptr` to `NULL`
spa_clear_fd(fd)
// calls `close(fd)` if `fd >= 0` and sets `fd` to -1
spa_steal_ptr(ptr)
// sets `ptr` to `NULL` and returns the old value,
// useful for preventing the auto cleanup mechanism from kicking in
// when returning the pointer from a function
spa_steal_fd(fd)
// sets `fd` to -1 and returns the old value
Barnabás Pőcze