James Bielman  <jamesjb@jamesjb.com> wrote:
+---------------
| You may also need to look into disabling garbage collection or
| instructing the GC not to move your array for the duration of the
| system call, for maximum safety.  I don't know about CMUCL, but in
| SBCL I would suggest the use of WITH-PINNED-OBJECTS.
+---------------

    cmu> (describe 'system:without-gcing)

    WITHOUT-GCING is an external symbol in the SYSTEM package.
    Macro-function: #<Function (:MACRO SYSTEM:WITHOUT-GCING) {102BE7A9}>
    Macro arguments:
      (&rest body)
    Macro documentation:
      Executes the forms in the body without doing a garbage collection.
    ...
    cmu> 

This should surround the call to (%FREAD (SYS:VECTOR-SAP array) ...).

Though note that in compiled code, VECTOR-SAP doesn't cons.
So since CMUCL is single-threaded (from the OS/s POV), in practice
it's safe even without the SYSTEM:WITHOUT-GCING, provided all the
other arguments to %FREAD have been precomputed as well. [This is
probably *not* the case in SBCL on platforms on which it supports
native threading.]


-Rob

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Rob Warnock			<rpw3@rpw3.org>
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