[Cython] patch for #655

[Felix Salfelder]

On Tue, Jun 25, 2013 at 01:06:35AM -0700, Robert Bradshaw wrote:
> One first comment, I think it's a lot to reserve three flags for this.
> Perhaps "-M [filename] would be sufficient, using the convention that
> - is stdout. If necessary, we could have a special syntax for the -D
> option.

it's a tradeoff between simplicity and force of habit. anybody using gcc
and make knows, what -M and -M[A-Z] mean. anybody who doesnt use any of
these, will never need this functionality.

but yes, of you *do* need -P and -D otherwise, we might find other
characters...

> I'm still, however, trying to figure out exactly what the usecase for
> this is.

it's about keeping track of build dependencies.

> Generally extensions are created with distutils, and
> cythonize handles the dependencies in that framework for you, so I'm
> not sure how you'd use the resulting makefiles (one per .pyx file?)
> anyways. 

cythonize doesnt know, which headers gcc will use when compiling the
cython output. now what any other compiler will do. i have no idea how
to fix that (design flaw?), and its currently easier to just use
makefiles from the beginning. with makefiles, dependencies are easy and
fast, if all involved compilers support it.

regards
felix