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niminst: bugfixes; documentation changes

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Araq 2012-01-15 01:03:57 +01:00
commit f58cc49672
9 changed files with 70 additions and 85 deletions
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35
doc/manual.txt
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@ -736,37 +736,10 @@ variadic proc, it is implicitely converted to ``cstring`` too:
Even though the conversion is implict, it is not *safe*: The garbage collector
does not consider a ``cstring`` to be a root and may collect the underlying
memory:
.. code-block:: nimrod
var nimStr = "example"
var cStr: cstring = nimStr
var i = 0
while cStr[i] != '\0':
# since `nimStr`'s lifetime ended here the GC is allowed to free
# the memory occupied by "example":
GC_collect()
# now cStr points to garbage:
echo cStr[i]
inc i
However this a very contrived example; in practice this almost never happens.
One can use the builtin procs ``GC_ref`` and ``GC_unref`` to make this code
safe:
.. code-block:: nimrod
var nimStr = "example"
GC_ref(nimStr) # keep GC from freeing 'nimStr'
var cStr: cstring = nimStr
var i = 0
while cStr[i] != '\0':
# since `nimStr`'s lifetime ended here the GC is allowed to free
# the memory occupied by "example":
GC_collect()
# now cStr points to garbage:
echo cStr[i]
inc i
GC_unref(nimStr) # GC is allowed to free 'nimStr'
memory. However in practice this almost never happens as the GC considers
stack roots conservatively. One can use the builtin procs ``GC_ref`` and
``GC_unref`` to keep the string data alive for the rare cases where it does
not work.
Structured types