[BUG]: FP8 support introduced new GCC 6 / CUB warnings

[gevtushenko]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Type of Bug

Compile-time Error

Component

CUB

Describe the bug

GCC 6 emits warnings on the following code (nvbug 4384865):

unsigned char max_word = 0x7EU;
return reinterpret_cast<__nv_fp8_e4m3&>(max_word);

This affects only our tests. For users, the code is under system header.

How to Reproduce

#include <cub/util_type.cuh>

int main() { } 

When compiled with:

nvcc main.cu -ccbin=g++-6 -D_CCCL_NO_SYSTEM_HEADER -O3 -std=c++14 "--generate-code=arch=compute_89,code=[compute_89,sm_89]" -Xcompiler=-Werror -Xcompiler=-Wall -Xcompiler=-Wextra

Emits:

cccl/cub/cub/util_type.cuh:1187:51: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
         return reinterpret_cast<__nv_fp8_e4m3&>(max_word);

Expected behavior

Compilation emits no warnings

Reproduction link

No response

Operating System

No response

nvidia-smi output

No response

NVCC version

No response