[commit: ghc] master: Be less untruthful about the prototypes of external functions (5a31f23)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/5a31f231eebfb8140f9b519b166094d9d4fc2d79/ghc

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

commit 5a31f231eebfb8140f9b519b166094d9d4fc2d79
Author: Colin Watson <cjwatson at debian.org>
Date:   Sat Apr 12 01:55:07 2014 +0100

    Be less untruthful about the prototypes of external functions
    
    GHC's generated C code uses dummy prototypes for foreign imports.  At the
    moment these all claim to be (void), i.e. functions of zero arguments.  On
    most platforms this doesn't matter very much: calls to these functions put
    the parameters in the usual places anyway, and (with the exception of
    varargs) things just work.
    
    However, the ELFv2 ABI on ppc64 optimises stack allocation
    (http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01149.html): a call to a
    function that has a prototype, is not varargs, and receives all parameters
    in registers rather than on the stack does not require the caller to
    allocate an argument save area.  The incorrect prototypes cause GCC to
    believe that all functions declared this way can be called without an
    argument save area, but if the callee has sufficiently many arguments then
    it will expect that area to be present, and will thus corrupt the caller's
    stack.  This happens in particular with calls to runInteractiveProcess in
    libraries/process/cbits/runProcess.c.
    
    The simplest fix appears to be to declare these external functions with an
    unspecified argument list rather than a void argument list.  This is no
    worse for platforms that don't care either way, and allows a successful
    bootstrap of GHC 7.8 on little-endian Linux ppc64 (which uses the ELFv2
    ABI).
    
    Fixes #8965
    
    Signed-off-by: Colin Watson <cjwatson at debian.org>
    Signed-off-by: Austin Seipp <austin at well-typed.com>


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5a31f231eebfb8140f9b519b166094d9d4fc2d79
 includes/Stg.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/includes/Stg.h b/includes/Stg.h
index be966aa..1707c9b 100644
--- a/includes/Stg.h
+++ b/includes/Stg.h
@@ -213,7 +213,7 @@ typedef StgFunPtr       F_;
 #define II_(X)          static StgWordArray (X) GNU_ATTRIBUTE(aligned (8))
 #define IF_(f)    static StgFunPtr GNUC3_ATTRIBUTE(used) f(void)
 #define FN_(f)    StgFunPtr f(void)
-#define EF_(f)    extern StgFunPtr f(void)
+#define EF_(f)    extern StgFunPtr f()
 
 /* -----------------------------------------------------------------------------
    Tail calls