[cmake-developers] Setting the link interface and dependencies in one command

[Rolf Eike Beer]

Am Samstag, 1. Oktober 2011, 22:51:55 schrieb Clinton Stimpson:
> On Oct 1, 2011, at 4:48 PM, Rolf Eike Beer wrote:
> > On Sa.,   1. Okt. 2011 18:40:09 CEST, Alexander Neundorf 
<neundorf at kde.org> wrote:
> >> If library bar internally uses symbols from foo,
> >> it needs to link against foo.
> > 
> > Correct.
> > 
> >> But if bar doesn't expose symbols from foo in its
> >> interface, and my executable   hello links against bar, it doesn't
> >> also
> >> have to be linked against foo. This saves startup time and other
> >> things.
> >> Packagers also like that.
> > 
> > No, you got something wrong here. Packagers hate that. That's exactly
> > the reason why e.g. Fedora and others introduced -Wl,no-unneeded (or
> > how that's called) in their default linker flags.
> > 
> > If your hello needs foo and bar, and is only linked to bar because that
> > one is already linked against foo, that your package will not work any
> > longer if you replace foo 1.0 with foo 1.1 which is totally binary
> > compatible but doesn't need foo internally any longer because your
> > hello then misses symbols on startup. This is called unterlinking of
> > hello and should be avoided whereever possible.
> > 
> > The opposite is overlinking and that was what I tried to avoid: my hello
> > did not need any symbols from foo itself, so I wanted to get rid of
> > them (which worked by forcing the implicit dependencies to empty). But
> > CMake still did not want to allow me to export the bar target without
> > also exporting foo even if the linkage to foo was only an internal
> > detail and the user was not even allowed to use foo directly.
> 
> Can you consider this example as a demonstration for why cmake wants
> information about foo in the exports file even though its an internal
> detail?

Yes, I can. This wouldn't have been relevant for me, as all the libraries were 
installed to the same directory.

Thanks,

Eike
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