Re: [PATCH,Take 3] Fix make closures.c use dlmmap,dlmunmap on cygwin.

[Dave Korn <dave dot korn dot cygwin at googlemail dot com>]

Dave Korn wrote:
> [ refs: http://gcc.gnu.org/ml/gcc-patches/2009-06/threads.html#02228
>         http://gcc.gnu.org/ml/gcc-patches/2009-07/threads.html#00352 ]

  Interestingly, the problem doesn't reproduce directly on upstream libffi.
There must be something different in the #ifdeffery, because what happens
instead is that dlmalloc doesn't select its own win32 mmap/munmap
replacements, but instead calls dlmmap and dlmunmap directly.  These are
apparently defined in a cygwin header file somewhere, but not actually
implemented or exported, so all the tests fail to link with undefined symbol
errors referring to dlmmap/dlmunmap.

  With the patch applied, libffi uses its reimplementations of those functions
and relies on the underlying c library support for mmap/munmap, which works.
The test results are quite different, though:

> 		=== libffi Summary ===
> 
> # of expected passes		1563
> # of unexpected failures	66
> # of expected failures	10

  And I know everything is not quite right because these warnings appear
during the build, which made me look back and notice that they appeared in my
gcc build as well:

/gnu/libffi/libffi/src/closures.c: In function 'dlmmap_locked':
/gnu/libffi/libffi/src/closures.c:405:3: warning: implicit declaration of
function 'mmap'
/gnu/libffi/libffi/src/closures.c:405:7: warning: assignment makes pointer
from integer without a cast
/gnu/libffi/libffi/src/closures.c:421:9: warning: assignment makes pointer
from integer without a cast
/gnu/libffi/libffi/src/closures.c:425:7: warning: implicit declaration of
function 'munmap'
/gnu/libffi/libffi/src/closures.c: In function 'dlmmap':
/gnu/libffi/libffi/src/closures.c:456:11: warning: assignment makes pointer
from integer without a cast


  Bah.  I think I should withdraw the patch while I try and figure out why
it's not picking up the declarations of those functions, and why the two
behave so differently.

    cheers,
      DaveK