[GHC] #2596: Token concatentation (##) in C preprocessor

[GHC]

#2596: Token concatentation (##) in C preprocessor
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    Reporter:  sedillard        |        Owner:         
        Type:  feature request  |       Status:  new    
    Priority:  normal           |    Milestone:         
   Component:  Compiler         |      Version:  6.8.3  
    Severity:  normal           |   Resolution:         
    Keywords:                   |     Testcase:         
Architecture:  Unknown          |           Os:  Unknown
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Comment (by malcolm.wallace at cs.york.ac.uk):

 This occurs because ghc calls the C preprocessor with the -traditional
 flag, and the ## string-catenation operator is not K&R, it was introduced
 in the ANSI version of C.  There are various good reasons why it is
 necessary for ghc to use cpp -traditional rather than -ansi. You can try
 passing the -ansi flag manually ({{{ghc -optP-ansi}}}) but results are not
 guaranteed to be useful.  Another route to try is to install cpphs and
 instruct ghc to use it instead of cpp.  {{{ghc -pgmPcpphs -optP--cpp
 -optP-ansi}}}

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2596#comment:1>
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