[GHC] #12377: getExecutablePath doesn't return absolute path on OpenBSD (and maybe other OS also)

[GHC]

#12377: getExecutablePath doesn't return absolute path on OpenBSD (and maybe other
OS also)
-------------------------------------+-------------------------------------
           Reporter:  oherrala       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  8.0.1
  libraries/base                     |
           Keywords:                 |  Operating System:  OpenBSD
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 System.Environment.getExecutablePath doesn't return absolute path to
 executable in OpenBSD. This happens because getExecutablePath uses argv[0]
 to determine path and argv[0] might not be absolute path.

 My environment:

 {{{
 $ uname -a
 OpenBSD fizbuz.pilkki.ciz.fi 6.0 GENERIC.MP#2274 amd64
 $ ghc -V
 The Glorious Glasgow Haskell Compilation System, version 7.10.3
 }}}

 This test program in OpenBSD:

 {{{#!hs
 module Main where
 import System.Environment
 main = getExecutablePath >>= print
 }}}

 returns

 {{{
 $ ./test
 "./test"
 }}}

 For example in OS X the call returns absolute path:

 {{{
 $ ./test
 "/Users/oherrala/tmp/test"
 }}}

 OpenBSD is one of the operating systems which gets fall back to using
 argv[0] to determine exec's location:

 https://git.haskell.org/ghc.git/blob/HEAD:/libraries/base/System/Environment/ExecutablePath.hsc#l152

 Maybe the argv[0] result should be wrapped with realpath(3) to get
 absolute path?


 This bug is also present in cabal-install and reported here:
 https://github.com/haskell/cabal/issues/3512#issuecomment-231604356

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12377>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler