[GHC] #4906: peekCString crashes on handling nullPtr

[GHC]

#4906: peekCString crashes on handling nullPtr
-------------------------------+--------------------------------------------
    Reporter:  sdjp            |       Owner:                
        Type:  bug             |      Status:  new           
    Priority:  normal          |   Component:  Compiler (FFI)
     Version:  6.12.3          |    Keywords:                
    Testcase:                  |   Blockedby:                
          Os:  Linux           |    Blocking:                
Architecture:  x86_64 (amd64)  |     Failure:  Runtime crash 
-------------------------------+--------------------------------------------
 Not quite sure what the 'correct' behaviour here is; but here's a minimal
 test case:


 {{{
 -bash-3.2$ more TestCase.hs
 import Foreign
 import Foreign.C

 main = do
     str <- peekCString nullPtr
     putStrLn str

 -bash-3.2$ ghc --make TestCase.hs
 -bash-3.2$ ./TestCase
 Segmentation fault

 }}}

 I was not expecting a seg fault here.  At minimum, peekCString
 documentation should describe what is meant to happen when you pass it a
 nullPtr (currently not mentioned at all).  Better would be some form of
 error reporting - I'm integrating with a C library, and it took me a while
 to track down what the root cause of the seg fault was.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4906>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler