[GHC] #12572: `readdir_r` is deprecated

[GHC]

#12572: `readdir_r` is deprecated
-------------------------------------+-------------------------------------
           Reporter:  erikd          |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Core           |           Version:  8.1
  Libraries                          |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Building GHC
  Unknown/Multiple                   |  failed
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 When building GHC git HEAD on Debian Testing I get:
 {{{
 libraries/unix/cbits/HsUnix.c: In function ‘__hscore_readdir’:

 libraries/unix/cbits/HsUnix.c:64:3: error:
      error: ‘readdir_r’ is deprecated [-Werror=deprecated-declarations]
        res = readdir_r(dirPtr, p, pDirEnt);
        ^~~

 In file included from libraries/unix/include/HsUnix.h:71:0: error:
     0,
                      from libraries/unix/cbits/HsUnix.c:9:

 /usr/include/dirent.h:183:12: error:
      note: declared here
      extern int readdir_r (DIR *__restrict __dirp,
                 ^~~~~~~~~
 }}}

 According to the man page:

 > This function is deprecated; use readdir(3) instead.
 >
 > The  readdir_r()  function  was  invented  as  a reentrant version of
 readdir(3).  It reads the next directory entry from the directory stream
 dirp,  and  returns  it  in  the  caller-allocated  buffer pointed to by
 entry.
 >
 > It  is expected that a future version of POSIX.1 will make readdir_r()
 obsolete, and require that readdir() be thread-safe when concurrently
 employed on different directory streams.

 In order to support all of the various *nix systems, we probably need to
 detect if `readdir_r` is deprecated and only use `readdir` where
 `readdir_r` is in fact deprecated.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12572>
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