Hide qhullcpp symbol

[jorisv]

Problem 1

qhullcpp is a static library that had been build with default symbol visibility strategies : all is visible.
When linking against this library, hpp-fcl get all libqhull symbols and also show them as visible.

If a thirdparty library is linking against hpp-fcl and qhullcpp, then a strange symbol mix-up can occur.
I have been able to reproduce it with pinocchio 3.

This can lead to binary conflicts, since there is no guarantee that pinocchio 3 and hpp-fcl are using the same version of qhullcpp with the same ABI (same compiler flags).

Solution

I advise to hide all qhullcpp symbols when linking against it.
I only know how to do it and test it on Linux. We should find a way to fix it on MacOS and Windows if the same issue occur.

Problem 2

hpp-fcl embed qhullcpp source code. This source code is working with some old qhull_r versions. I have not be able to build it with qhull_r 2020.2.

Solution

Maybe we can get rid of it ? Or at least document which version of qhull_r is needed.

If we keep it, then we should find a way to not export the qhullcpp symbol either (probably by creating a static library).

[jorisv]

It's maybe possible to hide symbol in macos with -hidden-lx linker flag.

On Windows, I think that symbol are hidden by default (no dllexport).