[GHC] #15348: Enable two-step allocator on FreeBSD

[GHC]

#15348: Enable two-step allocator on FreeBSD
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  FreeBSD           |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4939
       Wiki Page:                    |
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Changes (by vdukhovni):

 * Attachment "patch-rts__posix__OSMem.2.c" added.

 [Updated] OSMem.c patch with MAP_GUARD used alone rather than in
 combination with MAP_ANON|MAP_PRIVATE

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15348>
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