[BUG] `dynamic_cast` fails on Mac because of missing visibility annotations

[adalisk-emikhaylov]

Environment

Operating System: MacOS x64 12.7.6
Version / Commit SHA: VDB 12.0.0 (from brew)
Other: Apple clang version 13.1.6 (clang-1316.0.21.2.5)

Describe the bug

After loading a grid using openvdb::io::Stream::getGrids(), we're unable to dynamic_cast (it returns null) it to the type openvdb::FloatGrid, despite typeid(...).name() reporting the same name for both.

To Reproduce

Steps to reproduce the behavior:

1. Build your code with -fvisibility=hidden on a Mac.
2. Load a grid using openvdb::io::Stream::getGrids() then try to dynamic_cast it to openvdb::FloatGrid.
3. Observe that the cast returns null, but at the same time typeid(openvdb::FloatGrid).name() and typeid(your_grid).name() return the same string.

Expected behavior

The dynamic_cast succeeds.

Additional context

This bug is caused by the missing __attribute__((__visibility__("default"))) annotation on your classes. Adding the annotation makes the cast pass.

I added annotations to the following classes:

openvdb::Grid
openvdb::tree::Tree
openvdb::tree::RootNode
openvdb::tree::InternalNode
openvdb::tree::LeafNode

This is the type that openvdb::FloatGrid expands to, plus all its template arguments. I haven't tested if marking all those classes is necessary, but IIRC even the template arguments need to be marked.

I'm not well-versed in openvdb, so I don't know if any other classes have the same issue or not.

[Idclip]

Hey @adalisk-emikhaylov thanks for this - you're right that these classes should probably be marked with default visibility. However, as an aside, I would recommend against using dynamic_cast in general if you're passing VDB objects across dso boundaries. Instead use the openvdb::gridPtrCast and openvdb::gridConstPtrCast - these avoid calling dynamic_cast.