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ARC: cycle detector (#12823)

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* first implementation of the =trace and =dispose hooks for the cycle collector
* a cycle collector for ARC: progress
* manual: the .acyclic pragma is a thing once again
* gcbench: adaptations for --gc:arc
* enable valgrind tests for the strutils tests
* testament: better valgrind support
* ARC refactoring: growable jumpstacks
* ARC cycle detector: non-recursive algorithm
* moved and renamed core/ files back to system/
* refactoring: --gc:arc vs --gc:orc since 'orc' is even more experimental and we want to ship --gc:arc soonish
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Andreas Rumpf 2019-12-17 17:37:50 +01:00 • committed by GitHub
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28
doc/manual.rst
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@ -6017,8 +6017,32 @@ The ``noreturn`` pragma is used to mark a proc that never returns.
acyclic pragma
--------------
The ``acyclic`` pragma applies to type declarations. It is deprecated and
ignored.
The ``acyclic`` pragma can be used for object types to mark them as acyclic
even though they seem to be cyclic. This is an **optimization** for the garbage
collector to not consider objects of this type as part of a cycle:
.. code-block:: nim
type
Node = ref NodeObj
NodeObj {.acyclic.} = object
left, right: Node
data: string
Or if we directly use a ref object:
.. code-block:: nim
type
Node {.acyclic.} = ref object
left, right: Node
data: string
In the example a tree structure is declared with the ``Node`` type. Note that
the type definition is recursive and the GC has to assume that objects of
this type may form a cyclic graph. The ``acyclic`` pragma passes the
information that this cannot happen to the GC. If the programmer uses the
``acyclic`` pragma for data types that are in reality cyclic, the memory leaks
can be the result, but memory safety is preserved.
final pragma

8
doc/nimc.rst
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@ -237,8 +237,8 @@ This uses the configuration defined in ``config\nim.cfg`` for ``lvm_gcc``.
If nimcache already contains compiled code from a different compiler for the same project,
add the ``-f`` flag to force all files to be recompiled.
The default compiler is defined at the top of ``config\nim.cfg``. Changing this setting
affects the compiler used by ``koch`` to (re)build Nim.
The default compiler is defined at the top of ``config\nim.cfg``.
Changing this setting affects the compiler used by ``koch`` to (re)build Nim.
Cross compilation
@ -557,9 +557,9 @@ For example, to generate code for an `AVR`:idx: processor use this command::
For the ``standalone`` target one needs to provide
a file ``panicoverride.nim``.
See ``tests/manyloc/standalone/panicoverride.nim`` for an example
implementation. Additionally, users should specify the
implementation. Additionally, users should specify the
amount of heap space to use with the ``-d:StandaloneHeapSize=<size>``
command line switch. Note that the total heap size will be
command line switch. Note that the total heap size will be
``<size> * sizeof(float64)``.