Re: MSW DLLs support in libtool

[Bob Friesenhahn]

On Tue, 9 Feb 2016, Vadim Zeitlin wrote:
> 2. Enabling this option is not enough as you must also painstakingly add
>   -no-undefined to all LDFLAGS. Why does libtool need to force you to do
>   it instead of just using it unconditionally for all MSW DLLs knowing
>   that they can *never* have any undefined symbols? While using this
>   option is a good idea for the other platforms too anyhow, there just
>   doesn't seem to be any reason to not use it implicitly for MSW, is
>   there?

This is an indication that appropriate steps have been taken to apply 
all needed dependencies at link time.  This is often not the case. 
Systems like GNU/Linux support implicit dependencies and so sometimes 
an effort is made to not include dependencies, or they may be missed 
by accident.

> 4. After all the previous steps I could finally cajole libtool into
>   building the DLLs for my lib_LTLIBRARIES but it still silently builds
>   static libraries for all my noinst_LTLIBRARIES and I have no idea why.

These are likely "convenience" libraries which are not used as normal 
archive libraries at link time.  Instead all of the objects are 
extracted and applied at link time.  The archive library is used as a 
container rather than a normal archive library.

> The most aggravating thing is that libtool really seems to go out of its
> way to make MSW DLLs creation more difficult than it needs to be with all
> the tests for things that can never happen. I realize that DLLs are very
> different from the typical Unix shared libraries which are libtool's bread
> and butter, but surely they're important enough in practice to have some
> special handling for them?

There is special handling.  You already reported the -no-undefined 
special handling. :-)

> If libtool has a goal of providing decent support for MSW DLLs, I could
> try submitting patches changing the things above to work in a more
> user-friendly way, but I'd really like to know if they would be welcome
> first or if, perhaps, the way things [don't] work now is a subtle hint that
> libtool just shouldn't be used if first-tier MSW support is required.

It is important that change for Windows do not break the many other 
supported platforms.  Your changes are welcome if they assure this and 
improve reliability and usability.

There is a long-standing principle in the history of libtool that it 
should provide consistent functionality across platforms and not do 
things which encourage usages in one dominant platform which do not 
work on the others.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/