`readdir_r` is deprecated

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.

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
Test case
Differential revisions
BlockedBy
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Blocking
CC	ekmett
Operating system
Architecture