Fix POSITION_INDEPENDENT_CODE

[fjtrujy]

Description

This PR just fixed a wrong configuration in the cmake files with the POSITION_INDEPENDENT_CODE, it should be just enabled when the BUILD_SHARED_LIBS config is enabled as well.

The specific details about the issue can be found here:
#1344

Thanks

[cdunn2001]

Thank you! We depend on users for cmake maintenance. We use meson ourselves.

The TravisCI troubles should be fixed. Please rebase, then merge after the CI tests pass.

[fjtrujy]

Thank you! We depend on users for cmake maintenance. We use meson ourselves.

The TravisCI troubles should be fixed. Please rebase, then merge after the CI tests pass.

Maybe it is a off topic question, but why don't you use GitHub Actions rather than TravisCI and implement a matrix with all possible combinations meson, cmake and different OS?

If you're interested I could easily do it.

Thanks

[fjtrujy]

Hello @cdunn2001,
I have rebased the PR and now all the CI checks are green, could you merge the PR?

Thanks

[cdunn2001]

If you're interested I could easily do it.

Yes! Very interested. We would gladly accept your help.

[cdunn2001]

I think we already test cmake in AppVeyor. But as long as the tests run fast, more robustness would be welcome.

[SpaceIm]

Does it really make sense? I would have removed it, that's all (same behavior than STATIC). I mean, BUILD_SHARED_LIBS is orthogonal to BUILD_OBJECT_LIBS.

[SpaceIm]

it's the BUILD_SHARED_LIBS branch, so it's always ON in this block. And actually forcing POSITION_INDEPENDENT_CODE for a shared lib is useless because it's implicit in CMake. Therefore this line could be removed, it's misleading.

[fjtrujy]

@SpaceIm about your suggestions..... in my opinion, the best solution is just to put at the root level, and just once this:

POSITION_INDEPENDENT_CODE ${BUILD_SHARED_LIBS}

I didn't want to do that change because I just took a quick way.

Thanks

[SpaceIm]

I disagree. I like principle of least surprise:

• shared libs are always PIC
• static and object libs are not PIC by default (unless they are linked to a shared lib internally, therefore build system must manually force PIC).
• PIC can be enabled for object and static libs (and it's a consumer decision through standard CMAKE_POSITION_INDEPENDENT_CODE variable).

[fjtrujy]

I disagree. I like principle of least surprise:

• shared libs are always PIC
• static and object libs are not PIC by default (unless they are linked to a shared lib internally, therefore build system must manually force PIC).
• PIC can be enabled for object and static libs (and it's a consumer decision through standard CMAKE_POSITION_INDEPENDENT_CODE variable).

Ok, I'm fine with whatever solution meanwhile there is a way by flags of disabling the CMAKE_POSITION_INDEPENDENT_CODE.

Thanks

[cdunn2001]

@SpaceIm , I didn't realize there was controversy. If you feel strongly about this, please submit a PR with a better solution. We try to let the cmake community reach consensus.