[commit: base] master: Change a few FFI imports to use CAPI (3581ef2)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/3581ef278ff57ecd8630482cac93d88813e72263

>---------------------------------------------------------------

commit 3581ef278ff57ecd8630482cac93d88813e72263
Author: Ian Lynagh <igloo at earth.li>
Date:   Sun May 20 13:48:20 2012 +0100

    Change a few FFI imports to use CAPI
    
    On Win64, ssize_t is 64 bit, but functions like read return 32 bit
    ints. The CAPI wrapper means the C compiler takes care of doing all
    the necessary casting.
    
    Technically we should instead be making the types of the FFI imports
    different on different platforms, but I think this will work out
    simpler overall.
    
    Before this fix, when the functions failed with -1, we thought they
    were returning with 4294967295, and so didn't throw an exception.
    This lead to a segfault in echo001(ghci).

>---------------------------------------------------------------

 System/Posix/Internals.hs |   24 ++++++++++++++++++++----
 1 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/System/Posix/Internals.hs b/System/Posix/Internals.hs
index d2bd0e6..5583c3b 100644
--- a/System/Posix/Internals.hs
+++ b/System/Posix/Internals.hs
@@ -435,10 +435,12 @@ foreign import ccall unsafe "HsBase.h __hscore_open"
 foreign import ccall safe "HsBase.h __hscore_open"
    c_safe_open :: CFilePath -> CInt -> CMode -> IO CInt
 
-foreign import ccall unsafe "HsBase.h read" 
+-- See Note: CSsize
+foreign import capi unsafe "HsBase.h read"
    c_read :: CInt -> Ptr Word8 -> CSize -> IO CSsize
 
-foreign import ccall safe "HsBase.h read"
+-- See Note: CSsize
+foreign import capi safe "HsBase.h read"
    c_safe_read :: CInt -> Ptr Word8 -> CSize -> IO CSsize
 
 foreign import ccall unsafe "HsBase.h __hscore_stat"
@@ -447,10 +449,12 @@ foreign import ccall unsafe "HsBase.h __hscore_stat"
 foreign import ccall unsafe "HsBase.h umask"
    c_umask :: CMode -> IO CMode
 
-foreign import ccall unsafe "HsBase.h write" 
+-- See Note: CSsize
+foreign import capi unsafe "HsBase.h write"
    c_write :: CInt -> Ptr Word8 -> CSize -> IO CSsize
 
-foreign import ccall safe "HsBase.h write"
+-- See Note: CSsize
+foreign import capi safe "HsBase.h write"
    c_safe_write :: CInt -> Ptr Word8 -> CSize -> IO CSsize
 
 foreign import ccall unsafe "HsBase.h __hscore_ftruncate"
@@ -583,3 +587,15 @@ foreign import capi  unsafe "stdio.h value SEEK_CUR" sEEK_CUR :: CInt
 foreign import capi  unsafe "stdio.h value SEEK_SET" sEEK_SET :: CInt
 foreign import capi  unsafe "stdio.h value SEEK_END" sEEK_END :: CInt
 
+{-
+Note: CSsize
+
+On Win64, ssize_t is 64 bit, but functions like read return 32 bit
+ints. The CAPI wrapper means the C compiler takes care of doing all
+the necessary casting.
+
+When using ccall instead, when the functions failed with -1, we thought
+they were returning with 4294967295, and so didn't throw an exception.
+This lead to a segfault in echo001(ghci).
+-}
+