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Enabled explicitly unknown lock levels (#5409)

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* enabled explicitly unknown lock levels
* allowing "unknown" as locks pragma
* added test case for locks pragma
* updated docs on locks pragma
This commit is contained in:
Fabian Keller 2017-02-20 09:31:52 +01:00 • committed by Andreas Rumpf
commit ce4587d7b7
3 changed files with 39 additions and 1 deletions
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19
doc/manual/locking.txt
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@ -198,3 +198,22 @@ This is essential so that procs can be called within a ``locks`` section:
As usual ``locks`` is an inferred effect and there is a subtype
relation: ``proc () {.locks: N.}`` is a subtype of ``proc () {.locks: M.}``
iff (M <= N).
The ``locks`` pragma can also take the special value ``"unknown"``. This
is useful in the context of dynamic method dispatching. In the following
example, the compiler can infer a lock level of 0 for the ``base`` case.
However, one of the overloaded methods calls a procvar which is
potentially locking. Thus, the lock level of calling ``g.testMethod``
cannot be inferred statically, leading to compiler warnings. By using
``{.locks: "unknown".}``, the base method can be marked explicitly as
having unknown lock level as well:
.. code-block:: nim
type SomeBase* = ref object of RootObj
type SomeDerived* = ref object of SomeBase
memberProc*: proc ()
method testMethod(g: SomeBase) {.base, locks: "unknown".} = discard
method testMethod(g: SomeDerived) =
if g.memberProc != nil:
g.memberProc()