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Clarify manual's explanation of unwinding during failure. Add bit about soft vs. hard failure.

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Roy Frostig 2010-07-02 18:33:09 -07:00
parent 667d46bef9
commit c5a3c9736a
1 changed files with 17 additions and 8 deletions
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doc/rust.texi
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@ -1352,7 +1352,8 @@ channel is equal to the message type of the port it is bound to.
Messages are sent asynchronously or semi-synchronously. A channel contains a Messages are sent asynchronously or semi-synchronously. A channel contains a
message queue and asynchronously sending a message merely inserts it into the message queue and asynchronously sending a message merely inserts it into the
channel's queue; message receipt is the responsibility of the receiving task. sending channel's queue; message receipt is the responsibility of the
receiving task.
Queued messages in channels are charged to the domain of the @emph{sending} Queued messages in channels are charged to the domain of the @emph{sending}
task. If too many messages are queued for transmission from a single sending task. If too many messages are queued for transmission from a single sending
@ -1399,12 +1400,20 @@ un-trapped signal or the execution of a @code{fail} statement. Once
@emph{failing}, a task unwinds its stack and transitions to the @emph{dead} @emph{failing}, a task unwinds its stack and transitions to the @emph{dead}
state. Unwinding the stack of a task is done by the task itself, on its own state. Unwinding the stack of a task is done by the task itself, on its own
control stack. If a value with a destructor is freed during unwinding, the control stack. If a value with a destructor is freed during unwinding, the
code for the destructor is run, also on the task's control stack. If the code for the destructor is run, also on the task's control
destructor code causes any subsequent state transitions, the task of unwinding stack. Running the destructor code causes a temporary transition to a
and failing may suspend temporarily, and may involve (recursive) unwinding of @emph{running} state, and allows the destructor code to cause any
the stack of a failed destructor. Nonetheless, the outermost unwinding subsequent state transitions. The original task of unwinding and
activity will continue until the stack is unwound and the task transitions to failing thereby may suspend temporarily, and may involve (recursive)
the @emph{dead} state. There is no way to ``recover'' from task failure. unwinding of the stack of a failed destructor. Nonetheless, the
outermost unwinding activity will continue until the stack is unwound
and the task transitions to the @emph{dead} state. There is no way to
``recover'' from task failure. Once a task has temporarily suspended
its unwinding in the @emph{failing} state, failure occurring from
within this destructor results in @emph{hard} failure. The unwinding
procedure of hard failure frees resources but does not execute
destructors. The original (soft) failure is still resumed at the
point where it was temporarily suspended.
A task in the @emph{dead} state cannot transition to other states; it exists A task in the @emph{dead} state cannot transition to other states; it exists
only to have its termination status inspected by other tasks, and/or to await only to have its termination status inspected by other tasks, and/or to await
@ -1454,7 +1463,7 @@ An @dfn{item} is a component of a module. Items are entirely determined at
compile-time, remain constant during execution, and may reside in read-only compile-time, remain constant during execution, and may reside in read-only
memory. memory.
There are 5 primary kinds of item: modules, functions, iterators, objects and There are five primary kinds of item: modules, functions, iterators, objects and
types. types.
All items form an implicit scope for the declaration of sub-items. In other All items form an implicit scope for the declaration of sub-items. In other