Re: [Bug-ddrescue] Patch to support -d on Darwin and Mac OS X

[Antonio Diaz Diaz]

Christian Franke wrote:
> Both O_DIRECT and F_NOCACHE are not part of POSIX, so there probably is 
> no portable way without at least one more nasty #ifdef.

Yes, but O_DIRECT seems to be the "de facto standard" among unices, 
while F_NOCACHE is only used by Apple.


> POSIX provides only O_SYNC, I don't know whether this has any effect on 
> raw devices.

Ddrescue uses O_DIRECT only for the input file, so I think O_SYNC has no 
effect on it.


> Interestingly, F_NOCACHE does also not appear in GNU dd (coreutils 6.9). 
> Hmm...

What makes me think if I should contribute to spread the use of 
F_NOCACHE in detriment of the much more widely used O_DIRECT. I think it 
would be better that Apple implements O_DIRECT in Darwin, but I don't 
know what are the chances of this happening.


> An alternative patch is attached. It does not require DARWIN defined, 
> but relies on O_DIRECT undefined or defined as 0 in Darwin's includes. 

Thanks for this excellent patch. I suppose that if some future Darwin's 
headers define O_DIRECT it means that Darwin supports O_DIRECT, so your 
patch should also work in such a future Darwin version. :)


> BTW: On Cygwin, 1.6-pre2 builds OOTB and works.

Thanks for the feedback. Perhaps you would like to know that 1.6-pre3 is 
already released. ;)


Best regards,
Antonio.