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Improve documentation of mps_fix_call(): the called function must use mps_scan_begin and mps_scan_end itself.

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Nick Barnes 2015-10-13 15:19:12 +01:00
parent ffc148c008
commit b5fe5356ec
1 changed files with 11 additions and 6 deletions
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17
mps/manual/source/topic/scanning.rst
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@ -361,9 +361,9 @@ Scanning interface
.. c:function:: MPS_FIX_CALL(ss, call)
Call a function from within a :term:`scan method`, between
:c:func:`MPS_SCAN_BEGIN` and :c:func:`MPS_SCAN_END`, passing
the :term:`scan state` correctly.
Call a function to do some scanning, from within a :term:`scan
method`, between :c:func:`MPS_SCAN_BEGIN` and
:c:func:`MPS_SCAN_END`, passing the :term:`scan state` correctly.
``ss`` is the scan state that was passed to the scan method.
@ -377,6 +377,9 @@ Scanning interface
must wrap the call with :c:func:`MPS_FIX_CALL` to ensure that the
scan state is passed correctly.
The function being called must use :c:func:`MPS_SCAN_BEGIN` and
:c:func:`MPS_SCAN_END` appropriately.
In example below, the scan method ``obj_scan`` fixes the object's
``left`` and ``right`` references, but delegates the scanning of
references inside the object's ``data`` member to the function
@ -406,9 +409,11 @@ Scanning interface
.. warning::
Use of :c:func:`MPS_FIX_CALL` is best avoided, as it forces
values out of registers. The gains in simplicity of the code
need to be measured against the loss in performance.
Use of :c:func:`MPS_FIX_CALL` is best avoided, as it may
force values out of registers (depending on compiler
optimisations such as inlining). The gains in simplicity of
the code ought to be measured against the loss in
performance.
.. index::