[BuildTools] --enable-doscompile

[Andreas Waechter]

Hi Ted,

> I guess I prefer the default compile mode to be to link with Cygwin.dll (but 
> only slightly) because
>
> 1. There are some features of SYMPHONY that do not work otherwise, and most 
> users will not dig around enough to realize how they should change this.

What are the things that don't work with mingw compiler?  Maybe we can fix 
that?

> 2. If you are using CYGWIN, rather than Visual C++ Express, you are probably 
> planning to run the code from within CYGWIN (and want that features provided 
> therein). In this case, why would you care about the dependence on 
> CYGWIN.dll?

I disagree here.  For Ipopt and Bonmin, people usually want to generate 
the AMPL solver executable, and that one doesn't work with Cygwin.  Also, 
the executables seem to behave funny with the Cygwin.dll (e.g., output is 
flushed irregularly, and I think it is also slower).

Another reason NOT to use the Cygwin.dll by default is that we usually try 
to avoid unnecessary linkage with libraries that come with a different 
licence (e.g., by default, Clp is not using the readline library etc).

> 3. It is not nice to switch defaults on users in a patch release :) (of 
> course, I guess we might have done that once already).

I agree with you here.  I don't mind starting a new stable branch for 
BuildTools, but in reality this of course doesn't solve anything, since 
the dependent project will then all have to switch, too.

> Isn't there a way to make the default for a given project something different 
> than the global default? Then we could leave it as is and let each project 
> choose its own default.

I think this is a little difficult, because all projects that are compiled 
for one package need to be compiled in the same way.  But it might be 
possible to do this by setting an environment variable in the main 
configure script.  E.g., you could have

export enable_doscompile=no

in your Symphony's package directory's configure.ac file (after you 
checked that it hasn't been set differently by the user). This would have 
to be faily at the beginning of the configure.ac file.

> Anyway, I don't feel that strongly, so do as you must :).

Ok, I think I feel like changing it... :)  But I'll wait in case there are 
more responses.

Cheers

Andreas