The callback passed to asio_set_on_{failed, started}_callback was
never null because the way types for input parameters work in
extensions. Null from user PHP code was converted to a stdClass
object, triggering an exception.
Expose the following data to the PHP:
- asio_get_current_context_idx(): get current context index
- asio_get_running_in_context(): get running wait handle in a given context
- asio_get_running(): get running wait handle in a current context (renamed asio_get_current())
- WaitableWaitHandle::getContextIdx(): get context the wait handle operates in
- WaitableWaitHandle::getCreator(): get continuation wait handle that constructed this wait handle
Move the responsibility of entering/exiting contexts from PHP to the
implementation of $wait_handle->join().
This eliminates possibility of weird situations, like contexts without
any running wait handle. This guarantees that asio_get_current() returns
null only if called completely out of asio framework and simplifies some
logic, such as getCurrentWaitHandleDepth().
Currently, wait handles store pointer to the context they are in. This
pointer is not protected with reference counting, as it is expected that
whenever a context is exited, references to it are cleaned thru
exitContext() mechanism.
If a bug is present that violates this assumption, it is impossible to
guard against invalid pointer access and a hard to debug memory
corruption occurs.
Since the structure of contexts is a simple stack, let's reference them
by index instead of by pointer.
As a bonus, one pointer worth of memory is saved for every non-trivial wait handle.
The actual bugs will be fixed by the next 2 diffs that do:
1. implement online cycle detection
2. do enterContext() atomically and properly handle failure
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
Alex Suhan