Re: Using Boost.Test header-only from CMake

From: Peter Dimov (pdimov_at_[hidden])
Date: 2021-06-11 14:50:45

Rainer Deyke wrote:
> On 10.06.21 23:36, Andrey Semashev via Boost wrote:
> > CMake defines targets for header-only libraries, which can have
> > dependencies on other targets, including on static or shared libraries.
> > So the program that "links" to the header-only library picks up its
> > dependencies recursively. As a result, the linker is invoked with all
> > (binary) libraries in the dependency tree.
> 
> If this functionality works the way I think does, then I think it should not be
> used.

Not "linking" to header-only libraries properly only works when all the
headers are dumped into a central location, e.g. /usr/include or, in our
case, $BOOST_ROOT/boost. That it works with our b2 setup is an artifact
of this physical organization (and requires our `b2 headers` step).

If the libraries are properly separated, which should really be required
by any sane package management scheme, you have to "link" to
header-only libraries in order to get the proper directory into your
include path.

As a side effect, this also makes the compiled -> header-only -> compiled
case work without any effort from the end user (who would otherwise be
forced to change his link line if an update to 'header-only' changes the list
of compiled libraries that need to be linked).