RE: portability notes

["Dave Korn" <dave dot korn at artimi dot com>]

On 15 February 2006 16:48, skaller wrote:

> On Wed, 2006-02-15 at 07:22 -0700, Eric Blake wrote:

>> There is no such thing as ming - it is mingw or mingw32.  Furthermore,
>> cygwin only provides -mno-cygwin as a convenience, but it is NOT SUPPORTED
>> on this list.  Ask the mingw list instead.
> 
> I wasn't asking for support/bug fixes or whatever -- 

  That's a shame, because this is the Cygwin support/bugfix list.

>I was
> asking for advice on the best programming practice to
> handle this kind of issue.

  This is /NOT/ a list about best programming practices, or the theory of
computer engineering, or any other such thing.  There *are* plenty of other
such lists, and they are populated with people who have the subject-specific
knowledge to actually _help_ you.

> But it isn't the same platform. On cygwin, the build
> scripts can be written with bash, and the generated
> executables can be run and passed Unix filenames.
> With MingW or MSVC++ targets, executables have to be
> passed Windows filenames.

  Yes, and if you build _on_ cygwin _using_ -mno-cygwin, you will get an
executable that has to be passed a windows filename.

  The cygwin dll hides this for you when you launch your exe from a bash
shell, because it knows when a new process is being created whether the
executable is a cygwin exe or a win32/mingw exe, and if it's win/ming, it
translates the paths for you.

> Since our product is itself a cross-cross-compiler,

  That's too cross!  Your product needs to take a chill pill!

> So, to give one of the original problems again: to emulate
> Posix on non-posix platforms, I found I had to define EAGAIN.

  Emulating posix on non-posix platforms is not the topic of the list.  This
is the cygwin list, and in the cygwin world, EAGAIN is defined in errno.h.

> I just did
> 
> #ifdef _WIN32
> #define EAGAIN TIMEOUT_WAIT
> #endif
> 
> but then we found Mingw seems to define it too. 

  That has nothing to do with Cygwin.

>So now the code reads:
> 
> #ifdef _WIN32
> #ifndef EAGAIN
> #define EAGAIN WAIT_TIMEOUT
> #endif
> #endif	
> 
> However it is a hack. It will do temporarily. A better
> solution would be to test if EAGAIN is already defined
> in the configuration script. Perhaps.

  ITYM 'indubitably'.

>  The problem is
> that I don't know if it is a macro, and I don't know
> which file it might be defined in (on a non-posix system
> one can't assume it is in the standard place, indeed that
> idea seems like a contradiction).

  Well, the only advice that Cygwin can give is to point you at the open-group
POSIX spec, which tells you where EAGAIN must be defined and in what way.  As
to what any non-POSIX systems out there might do, I have to ask you /yet
again/:

  Why are you asking this on the Cygwin list?



    cheers,
      DaveK
-- 
Can't think of a witty .sigline today....


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