[GHC] #5218: Add unpackCStringLen# to create Strings from string literals

[GHC]

#5218: Add unpackCStringLen# to create Strings from string literals
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        Reporter:  tibbe             |                Owner:  thoughtpolice
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.0.3
      Resolution:                    |             Keywords:  strings
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #5877 #10064      |  Differential Rev(s):  Phab:D2443
  #11312, #9719                      |
       Wiki Page:                    |
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Comment (by winter):

 > That's a separate issue. It is indeed what OverloadedStrings is for.
 Perhaps we can have a new ticket for it. But we can't talk meaningfully
 about it until we settle the first issue: what are the primitive types and
 operations over them. There I think we have a preliminary consensus, with
 B# = ByteArray#.

 My intention is to add a way to let user choose which primitive types
 he/she wants. But if there's a must to fix a primitive type, `ByteArray#`
 may be better than `Addr#` since it can be cast into `Addr#` not vice-
 versa(at the cost of extra info-header and length words).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5218#comment:94>
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