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Subject: Re: [boost] CMake and Boost Build tests
From: Florent Castelli (florent.castelli_at_[hidden])
Date: 2017-07-27 16:58:00

On Jul 27, 2017 16:41, "Edward Diener via Boost" <boost_at_[hidden]>

On 7/27/2017 8:43 AM, Florent Castelli via Boost wrote:

> On 26/07/2017 20:49, Edward Diener via Boost wrote:
>> Following John Maddock's appeal for practical solutions related to the
>> move to CMake, I would like to know what the CMake equivalent is to the
>> Boost Build unit test functionality.
>> In other words what do I write for CMake in order to do a Boost Build
>> compile, compile-fail, link, link-fail, run, and run-fail unit tests ?
> In my own Boost-CMake project, I have implemented regular "RUN" in a way
> that looks similar to the original Boost Build using functions:

What is RUN supposed to be in your link above ?

An equivalent of run from Boost Build. See

Other commands should be easy enough to implement as well, but I haven't
> had the interest in doing that in my project yet (which predates the SC
> decision).
> It is possible to do "compile" by creating a regular static library target
> with that file and then invoking "cmake --build . --target <compile test
> name>". Compile failures can be done similarly and check they fail.
> Link and Link-fail can be done the same way using actual binaries that are
> built, but not run.

This is a poor solution.

Could you please explain why? Using Cmake directly to build the sources
with the same flags as set in the toolchain is not controversial I'd say.
It's actually working better than other solutions I've seen trying to
reproduce the features.

> The difference is making sure you have a clear separation of building
> Boost itself and running the tests. I found out that failures are pretty
> common with those tests and many of them will fail to run without errors on
> all supported compiler and platform, so isolation is quite important.

Again I need to mention that the tests are run for header only libraries
which are not "built" at all in most cases.

That's irrelevant for CMake. You end up building the tests still, they will
depend on the header only library and its dependencies.

> The problem is that some build tools will not support parallel invocations
> (Ninja doesn't for example, see
> m/#!topic/ninja-build/4VP7whvWSH8 ) and thus running tests would be need
> to be linearized or moved to make, which should support that scenario
> better.

That is the end-users problem. I am just interested in Boost solving its
own problem of moving from the Boost Build testing rules to something with
CMake which does the same thing.

Not really, because if a solution that works correctly and doing perfect
forwarding of build flags can't be parallelized in some case, it would need
fixing. If a solution doesn't have perfect forwarding of compiler settings
and requirements, it's not really acceptable either.

>> Does CMake have an equivalent to the Boost Build alias rule ? or the
>> Boost Build project rule ?
>> The great majority of the Boost libraries are header-only libraries where
>> Boost Build is used to run the unit tests and, optionally, Boost Build is
>> used to build the documentation using a quickbook, boostbook, doxygen
>> toolset to generate html and pdf files. While I realize that building a
>> Boost library, and making that built library available to end-users via
>> CMake, has been the focus of most of the discussion so far regarding CMake
>> and Boost, I am assuming the move to CMake also means that running unit
>> tests and building docs where applicable must also be done through CMake.
>> If I am wrong about this then I personally will be only too happy to
>> continue using Boost Build to do these things.
> CMake support header-only libraries using the INTERFACE keyword of
> "add_library()". Those will propagate usage requirements like any other
> library to their users. You can have you tests depend on those easily.
> You can always have custom targets in each library to generate their
> documentation in any way you like.
> Building the documentation for the whole Boost project can be done by
> building all of those targets.

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