Realm: Duplicate registration of function _ZN3cub11EmptyKernelIvEEvv

[mariodirenzo]

After including cub/cub.cuh in most of the translation units of HTR I started getting multiple copies of this warning message at the startup of the solver.
Is this expected? Is there anything I can do to silence these error messages?

@elliottslaughter, can you please add this issue to #1032 with low priority?

[seemamirch]

This doesn't reproduce on sapling with legion (commit 3b3e14b)

[seemamirch]

This is occurring due to template instantiation.
The template function is defined in util_device.cuh as
template <typename T> __global__ void EmptyKernel(void) { }

and then instantiated in the same file
typedef void (*EmptyKernelPtr)(); EmptyKernelPtr empty_kernel = EmptyKernel<void>;

cub/cub.cuh includes util_device.cuh

If cub/cub.cuh is included in multiple files - we get the warning i.e.
[0 - 7fa23f7bbc40] 0.000000 {4}{gpu}: duplicate registration of function _ZN3cub11EmptyKernelIvEEvv
i.e.
https://gitlab.com/StanfordLegion/legion/-/blob/master/runtime/realm/cuda/cuda_module.cc?ref_type=heads#L2851

The symbol is marked as 'weak' and gets resolved by the linker.
Should this warning be removed? If a function has multiple definitions (not weak symbols) then the linker does give an error.

[lightsighter]

Does this only happen with the hijack on?

[seemamirch]

Does this only happen with the hijack on?

Yes only with hijack on

[lightsighter]

Since we're planning on removing the hijack (#1730) I think it's probably not worth removing the warning as it will go away automatically.