[GHC] #12577: The flag -xb has no effect on Windows

[GHC]

#12577: The flag -xb has no effect on Windows
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           Reporter:  Phyx-             |             Owner:
               Type:  bug               |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  Compiler          |           Version:  8.0.1
           Keywords:                    |  Operating System:  Windows
       Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:  #12576
Differential Rev(s):                    |         Wiki Page:
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 `-xb` is supposed to be used to change the base memory location for heap
 allocation calls. However all the calls in `rts\win32\OSMEM.c` call
 `VirtualAlloc` with `NULL` and not the desired start address.

 This makes the flag not do anything on Windows (based on quick inspection
 of allocated values).

 [[Image(http://i.imgur.com/e1O9Jlb.png, 720px)]]

 Allocation always starts at `0x020000`

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12577>
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