[GHC] #8627: mallocForeignPtrBytes documentation unobvious regarding memory alignment

[GHC]

#8627: mallocForeignPtrBytes documentation unobvious regarding memory alignment
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              Reporter:              |            Owner:  ekmett
  schernichkin                       |           Status:  new
                  Type:  bug         |        Milestone:
              Priority:  normal      |          Version:  7.6.3
             Component:  Core        |         Keywords:
  Libraries                          |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:
       Type of failure:              |
  Documentation bug                  |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by ekmett):

 `mallocForeignPtrBytes` provides no alignment guarantees. You should in
 theory need to pad your request by `(alignment - 1)` bytes and align the
 resulting memory by hand.

 We're missing a `mallocForeignPtrBytesAligned`, which would behave like
 `allocaBytesAligned` which probably should become a separate issue.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8627#comment:2>
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