[GHC] #15732: getArgsWithResponseFiles does not filter out RTS options

9 Oct 2018

      #15732: getArgsWithResponseFiles does not filter out RTS options
-------------------------------------+-------------------------------------
           Reporter:  ckoparkar      |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.8.1
          Component:                 |           Version:  8.6.1
  libraries/base                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #13896
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 I discovered this while working on a fix for #15072.

 {{{GHC.ResponseFile.getArgsWithResponseFiles}}} is a recent addition to
 {{{base-4.12}}}. The idea was to have a function which could read command-
 line arguments supplied via response files, but otherwise
 would behave exactly like `System.Environment.getArgs` (see #13896).
 However, these functions return different results when RTS options are
 supplied.
   1. {{{getArgs}}} does not include RTS options in the list it returns.
   2. {{{getArgsWithResponseFiles}}} includes them.

 It's trivial to reproduce this. Consider these files:

 {{{
 -- Bug1.hs
 module Main where

 import System.Environment ( getArgs )

 main :: IO ()
 main = do
   args <- getArgs
   putStrLn $ "Args: " ++ show args
 }}}

 and

 {{{
 -- Bug2.hs
 module Main where

 import GHC.ResponseFile ( getArgsWithResponseFiles )

 main :: IO ()
 main = do
   args <- getArgsWithResponseFiles
   putStrLn $ "ArgsResp: " ++ show args
 }}}

 And run them with:

 {{{#!sh
 $ ghc-8.6.1 -rtsopts Bug1.hs && ghc-8.6.1 -rtsopts Bug2.hs

 $ ./Bug1 1 +RTS -H32m -RTS 10 20
 Args: ["1","10","20"]

 -- 'opts_file' contains the same arguments passed to Bug1, and we
 -- use a '@' to pass it as a response file

 $ ./Bug2 @opts_file
 ArgsResp: ["1","+RTS","-H32m","-RTS","10","20"]
 }}}

 We should fix {{{getArgsWithResponseFiles}}} to properly handle {{{+RTS
 ... -RTS}}} and {{{--RTS}}} flags. Currently, {{{getArgs}}} relies on the
 [http://git.haskell.org/ghc.git/blob/HEAD:/rts/RtsFlags.c#l661 runtime
 system] for filtering out appropriate things.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15732
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