[GHC] #12495: GHC's configure script detects MADV_FREE when it shouldn't

[GHC]

#12495: GHC's configure script detects MADV_FREE when it shouldn't
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           Reporter:  orion          |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Build System   |           Version:  8.0.1
           Keywords:  MADV_FREE      |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Other
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 In osDecommitMemory there is a
 [http://git.haskell.org/ghc.git/blob/4986837f8168cacf95c24fecc84d7b36c47f3c11:/rts/posix/OSMem.c#l507
 #define] for MADV_FREE. The presence of MADV_FREE is detected by the
 [http://git.haskell.org/ghc.git/blob/4986837f8168cacf95c24fecc84d7b36c47f3c11:/configure.ac#l1052
 configure] script, however merely testing for the presence of this symbol
 does not prove that MADV_FREE is supported by the kernel (which was
 [https://kernelnewbies.org/Linux_4.5#head-
 42578a3e087d5bcc2940954a38ce794fe2cd642c introduced in 4.5]). On newer
 versions of GCC (e.g. 6.1.1 on Alpine Edge),
 [https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=981569c74cbb6bafa2ddcefa6dd9dbdc938ff1c8
 MADV_FREE is included in the compiler's header files], thus leading to a
 false positive.

 The impact of this bug is that when GHC is compiled with a more recent
 version of GCC, "unable to decommit memory: Invalid argument" errors will
 abound.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12495>
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