[GHC] #10560: -f and -O options interact in non-obvious, order dependent ways

[GHC]

#10560: -f and -O options interact in non-obvious, order dependent ways
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        Reporter:  bgamari           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by George):

 To a naive users who doesn't know how the -O* options are implemented it
 is very surprising. A language that is not order dependent should not have
 command line options that are! Haskell differs from other languages thus I
 don't know why Haskell command line option processing needs to agree with
 them. In any case we definitely need to document the current behavior of
 7.10.<n>

 I like Gidyn's suggestion above to process meta-flags before specific
 flags, regardless of their order on the command line.

 However as Ben writes above, perhaps it is best not to concentrate on
 order but on "the fact that -O and -f can silently conflict and one has
 know way of knowing this"

 Perhaps the simplest example of the issue is that the following do
 different things and there is currently no documentation that explains
 what that is. I think a warning or error would be appropriate.

 ghc -fspecialise -fno-specialise <filename>.hs
 ghc -fno-specialise -fspecialise <filename>.hs

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10560#comment:8>
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