Re: Using Boost.Test header-only from CMake

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2021-06-07 17:18:30

On 6/7/21 7:48 PM, John Maddock via Boost wrote:
> On 07/06/2021 17:26, Peter Dimov via Boost wrote:
>> Edward Diener wrote:
>>> Since it is totally legitimate to use Boost.Test in header only mode, 
>>> and many
>>> libraries currently do this, it is hardly a "waste of time" to 
>>> support this under
>>> CMake.
>> Under CMake you can't use header-only libraries without linking to 
>> their targets.
>> So there's no real benefit from having a separate header-only target 
>> to link to;
>> you can just link to the ordinary target Boost::unit_test_framework.
> 
> Doesn't that a) cause the unit test lib to be build when it doesn't need 
> to be, and b) add the resulting binary to library link list when it 
> doesn't need to be?
> 
> But I do appreciate the simplicity of a single target ;)

Another question is whether unnecessarily linking would cause duplicate 
symbols or ODR issues. I believe, you're not supposed to use header-only 
Boost.Test and then link against it, too, as the same symbols would be 
defined both in the test and the library.

Boost.Test could define two sets of targets - one for header-only and 
the other for separately built library. One benefit of that is that you 
could use different macros for these two targets, if needed (e.g. if the 
library sources need to discriminate between the two configs).