libffi was:Re: ANNOUNCE: GHC version 7.0.1

Simon Marlow marlowsd at
Thu Nov 25 07:02:40 EST 2010

On 18/11/2010 18:21, Tyson Whitehead wrote:
> On November 18, 2010 05:12:11 Simon Marlow wrote:
>> On 17/11/2010 14:34, Christian Maeder wrote:
>>> ghc can be built without and with libffi.
>> Which build option are you referring to here?  libffi is required for
>> FFI support in GHCi, and for FFI "wrapper" imports.  However on x86 and
>> x86_64 we don't normally use libffi for wrappers, because we have a
>> native implementation that is a bit faster (this is the
>> UseLibFFIForAdjustors build option).
> I was hoping someone might comment further on the selinux issues,
> I woudl gather from this though that the native implementation must now avoid
> the "selinux doesn't like pages that are both executable and writable" issue?

The native implementation of wrappers uses libffi for memory allocation, 
which works around the SELinux issues by using double-mapping of memory.


> (it seems like the solution that closed 738 was to use libffi)
> Cheers!  -Tyson

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