diff options
| -rw-r--r-- | compiler/sigmatch.nim | 28 | ||||
| -rw-r--r-- | doc/manual.txt | 59 | ||||
| -rw-r--r-- | todo.txt | 1 | ||||
| -rw-r--r-- | web/news.txt | 1 |
4 files changed, 71 insertions, 18 deletions
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim index a713fc0e2..9d1585c56 100644 --- a/compiler/sigmatch.nim +++ b/compiler/sigmatch.nim @@ -738,27 +738,17 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation = result = typeRel(c, f.sons[0], a.sons[0]) if result <= isConvertible: result = isNone # BUGFIX! - of tyPtr: - case a.kind - of tyPtr: - for i in 0..min(f.len, a.len)-2: + of tyPtr, tyRef: + if a.kind == f.kind: + # ptr[R, T] can be passed to ptr[T], but not the other way round: + if a.len < f.len: return isNone + for i in 0..f.len-2: if typeRel(c, f.sons[i], a.sons[i]) == isNone: return isNone result = typeRel(c, f.lastSon, a.lastSon) if result <= isConvertible: result = isNone elif tfNotNil in f.flags and tfNotNil notin a.flags: result = isNilConversion - of tyNil: result = f.allowsNil - else: discard - of tyRef: - case a.kind - of tyRef: - for i in 0..min(f.len, a.len)-2: - if typeRel(c, f.sons[i], a.sons[i]) == isNone: return isNone - result = typeRel(c, base(f), base(a)) - if result <= isConvertible: result = isNone - elif tfNotNil in f.flags and tfNotNil notin a.flags: - result = isNilConversion - of tyNil: result = f.allowsNil + elif a.kind == tyNil: result = f.allowsNil else: discard of tyProc: result = procTypeRel(c, f, a) @@ -774,7 +764,11 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation = of tyNil: result = f.allowsNil of tyProc: if a.callConv != ccClosure: result = isConvertible - of tyPtr, tyCString: result = isConvertible + of tyPtr: + # 'pointer' is NOT compatible to regionized pointers + # so 'dealloc(regionPtr)' fails: + if a.len == 1: result = isConvertible + of tyCString: result = isConvertible else: discard of tyString: case a.kind diff --git a/doc/manual.txt b/doc/manual.txt index 6526ba2cb..298f6329b 100644 --- a/doc/manual.txt +++ b/doc/manual.txt @@ -1366,6 +1366,65 @@ not nilable pointers. The details of this analysis are still to be specified here. +Memory regions +-------------- + +The types ``ref`` and ``ptr`` can get an optional `region`:idx: annotation. +A region has to be an object type. + +Regions are very useful to separate user space and kernel memory in the +development of OS kernels: + +.. code-block:: nimrod + type + Kernel = object + Userspace = object + + var a: ptr[Kernel, Stat] + var b: ptr[Userspace, Stat] + + # the following does not compile as the pointer types are incompatible: + a = b + +In order to make generic code easier tor write ``ptr T`` is a subtype +of ``ptr[R, T]`` for any ``R``. + +Furthermore the subtype relation of the region object types is lifted to +the pointer types: If ``A <: B`` then ``ptr[T, A] <: ptr[T, B]``. This can be +used to model subregions of memory. As a special typing rule ``ptr[R, T]`` is +not compatible to ``pointer`` to prevent the following from compiling: + +.. code-block:: nimrod + # from system + proc dealloc(p: pointer) + + # wrap some scripting language + type + PythonsHeap = object + PyObjectHeader = object + rc: int + typ: pointer + PyObject = ptr[PythonsHeap, PyObjectHeader] + + proc createPyObject(): PyObject {.importc: "...".} + proc destroyPyObject(x: PyObject) {.importc: "...".} + + var foo = createPyObject() + # type error here, how convenient: + dealloc(foo) + + +Future directions: + +* Memory regions might become available for ``string`` and ``seq`` too. +* Bultin regions like ``private``, ``global`` and ``local`` will + prove very useful for the upcoming OpenCL target. +* Bultin "regions" can model ``lent`` and ``unique`` pointers. +* Syntactially ``ptr`` might become an infix operator so that ``region ptr T`` + is transformed into ``ptr[region, T]``. + + + Procedural type --------------- A `procedural type`:idx: is internally a pointer to a procedure. ``nil`` is diff --git a/todo.txt b/todo.txt index 6629bdeeb..bc7c7979a 100644 --- a/todo.txt +++ b/todo.txt @@ -1,7 +1,6 @@ version 0.9.4 ============= -- document region pointers Bugs ==== diff --git a/web/news.txt b/web/news.txt index 4aaf10992..f7a9d05fa 100644 --- a/web/news.txt +++ b/web/news.txt @@ -145,6 +145,7 @@ Language Additions - Anonymous iterators are now supported and iterators can capture variables of an outer proc. - The experimental ``strongSpaces`` parsing mode has been implemented. +- You can annotate pointer types with regions for increased type safety. Tools improvements |