Mix of packages built with gcc-8 and gcc-9 lead to crashes when using std::filesystem

[j-rivero]

@nkoenig and other have been reported problems on the destruction of std::filesystem::path gazebosim/gz-sim#1310 (comment). The possible root cause is explained in https://stackoverflow.com/questions/63902528/program-crashes-when-filesystempath-is-destroyed and comes from the fact of building some binary packages with gcc-8 and others with gcc-9 and both software pieces using std::filesystem.

Bionic has gcc-7 so the trick for using gcc-8 should be fine there. Focal is affected. Debian Buster is gcc-8, so I don't expect problems there. As far as I can see the only affected platform is Focal.

Looking into the code the only software using the NEED_C17_COMPILER=true should be transport7 and ignition-gazebo all versions. Some manual checks:

Packages (using std::filesystem) affected:

• ignition-common in nightlies on Focal (after Update to use std::filesystem rather than Boost gazebosim/gz-common#238)
• ignition-gazebo6 stable on Focal (built with gcc-8)
• ignition-gazebo7 nightlies on Focal

Packages not affected.

• ignition-math6 on Focal (built with gcc-9)
• ignition-utils on Focal (built with gcc-9)
• sdformat12 stable on Focal. Built with gcc-9 but no std::filesystem.
• ignition-transport11 on Focal
• ignition-rendering6 on Focal
• ignition-sensors6 on Focal

[scpeters]

for whatever reason, ign-gazebo6 is using std::filesystem in https://github.com/ignitionrobotics/ign-gazebo/blob/ign-gazebo6/src/Util.cc#L21

[arjo129]

Seems like we are using it to check if a path is relative: https://github.com/ignitionrobotics/ign-gazebo/blob/faaa3ec2c9006db0be71be318e7f00be51d2a8e3/src/Util.cc#L365 . Would using the check we use for Apple help in this case? Seems like the Apple platform doesn't need std::filesystem.

[j-rivero]

Thanks @arjo129 for removing the use of std::filesystem in utils.cc. I think we are done here after latest releases using the right version of compiler. Please reopen if needed.