Code generation failure for box_t::extend via nvc++ OpenMP

Following the discussion in #43 about the issue there being potentially a compiler bug I decided to try and compile the downstream library I am working on XDG using nvc++ rather than llvm/clang and I came across what seemed to be a code generation bug when using the method box_t::extend() for creation of bounding boxes on device.

I have created a minimal working example here - https://github.com/Waqar-ukaea/cuBQL-issue-reproducer. The specific main file can be found here - https://github.com/Waqar-ukaea/cuBQL-issue-reproducer/blob/main/reproducers/bounds_extend_fail.cpp. When running the executable after compilation with clang vs nvc++:

Compiling with llvm/clang-22 there is no issues. However compilation with nvc++ seems to fail.

EDIT - nvc++ seems to have no issue when the CMake build type is set to Debug (-g -O0) with no optimization but when set to Release (-fast -O3) it fails to compile with the error shown above.

Start with reproducers/bounds_extend_fail.cpp in the linked minimal reproducer and compare execution after building with llvm/clang-22 and nvc++. Check the CMake Debug (-g -O0) and Release (-fast -O3) configurations; done means the nvc++ Release behavior is reproduced and the library-side cause or compiler-specific failure is clearly identified.