expose strlen from Foreign.C.String

[Viktor Dukhovni]

On Fri, Jan 22, 2021 at 06:07:22PM -0800, Eric Mertens wrote:

> I’m on board with this import, but we’ll need to get the type right if
> we’re going to bind to libc’s strlen directly
> 
> foreign import unsafe "strlen"
>   cstringLength :: CString -> IO CSize

Yes, definitely.  The final all-nits-addressed variant would be:

    foreign import ccall unsafe "string.h strlen"
      cstringLength :: CString -> IO CSize

which is differs from the example in section 8.4.3 of the Haskell 2010
report

    https://www.haskell.org/onlinereport/haskell2010/haskellch8.html#x15-1590008.4.3

    foreign import ccall "string.h strlen"
      cstrlen :: Ptr CChar -> IO CSize

only in the addition of "unsafe" and the name of the resulting function.

-- 
    Viktor.