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Diffstat (limited to 'doc/manual/locking.txt')
| -rw-r--r-- | doc/manual/locking.txt | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/doc/manual/locking.txt b/doc/manual/locking.txt index c00efdd91..c1bd5ca46 100644 --- a/doc/manual/locking.txt +++ b/doc/manual/locking.txt @@ -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() |