[HostJit] Windows support

[miscco]

This is initial work to suppport HostJit on windows.

We need to mostly work around some dll issues with missing symbols.

We are still failing some tests that need to be investigated, but this serves as a good start

[coderabbitai]

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Walkthrough

Windows JIT compilation is fixed by adding an _fltused stub, -fno-threadsafe-statics flag, cudaFuncSetAttribute import symbol, and MSVC C4459 suppression. Visibility and attribute macros in libcudacxx are refactored from COMPILER(MSVC) gating to OS(WINDOWS)/COMPILER(NVRTC) gating. cstdint gains Windows-specific int_fast*/uint_fast* type aliases. CubCall code generation switches from an EXPORT macro to _CCCL_VISIBILITY_EXPORT.

Changes

Windows JIT compilation and type alias support

Layer / File(s)	Summary
Windows JIT: _fltused stub, compiler flags, and import symbol c/parallel.v2/src/hostjit/include/hostjit/cuda_minimal/stubs/stdlib.h, c/parallel.v2/src/hostjit/compiler.cpp, c/parallel.v2/CMakeLists.txt	stdlib.h declares extern "C" int _fltused = 0 under _WIN32; compiler.cpp appends -fno-threadsafe-statics to the Windows host compiler args and adds cudaFuncSetAttribute to the minimal cudart.lib import symbol list; CMakeLists.txt suppresses MSVC C4459 via /wd4459.
int_fast*/uint_fast* Windows type aliases and freestanding branch libcudacxx/include/cuda/std/cstdint	Windows-specific underlying types selected for int_fast8/16/32/64_t and uint_fast8/16/32/64_t via _CCCL_OS(WINDOWS); non-hosted preprocessor path changed from #elif _CCCL_COMPILER(NVRTC) to #else with _CCCL_FREESTANDING() label; INT_FAST*/UINT_FAST* min/max macros split into Windows vs non-Windows branches.

OS-aware visibility and attribute macro refactoring

Layer / File(s)	Summary
Visibility and attribute macro refactoring to OS-based conditions libcudacxx/include/cuda/std/__cccl/visibility.h, libcudacxx/include/cuda/std/__internal/features.h	visibility.h includes os.h and switches _CCCL_VISIBILITY_HIDDEN/_DEFAULT/_EXPORT, _CCCL_NOINLINE, and _CCCL_PUBLIC_* macros from COMPILER(MSVC) to OS(WINDOWS) and COMPILER(NVRTC) gating; features.h includes os.h and updates its platform block guard from _CCCL_COMPILER(MSVC) to _CCCL_OS(WINDOWS).
CubCall code generation: EXPORT to _CCCL_VISIBILITY_EXPORT c/parallel.v2/src/hostjit/codegen/cub_call.cpp, c/parallel.v2/src/hostjit/include/hostjit/codegen/cub_call.hpp	Generated extern "C" function signatures now emit _CCCL_VISIBILITY_EXPORT instead of EXPORT; shared_includes() and multi-CubCall comments updated to reflect that visibility is controlled via _CCCL_VISIBILITY_EXPORT and symbols resolve under global C-linkage for dlsym lookup.

Possibly related PRs

• NVIDIA/cccl#9487: Refactors visibility macros in the same header and switches alignment helpers to use the updated public API macros.

Suggested reviewers

• bernhardmgruber
• fbusato
• shwina

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[coderabbitai]

Actionable comments posted: 3

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ℹ️ Review info

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Run ID: eb88a771-d376-4cb3-b893-2479707055a8

📥 Commits

Reviewing files that changed from the base of the PR and between 6e245c5 and 3399566.

📒 Files selected for processing (4)

• c/parallel.v2/CMakeLists.txt
• c/parallel.v2/src/hostjit/compiler.cpp
• c/parallel.v2/src/hostjit/include/hostjit/cuda_minimal/stubs/stdlib.h
• libcudacxx/include/cuda/std/cstdint

[coderabbitai]

Actionable comments posted: 1

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 29d027cb-f1de-44fc-b640-3b50620eac8a

📥 Commits

Reviewing files that changed from the base of the PR and between 3399566 and 587ae93.

📒 Files selected for processing (9)

• c/parallel.v2/CMakeLists.txt
• c/parallel.v2/src/hostjit/codegen/cub_call.cpp
• c/parallel.v2/src/hostjit/compiler.cpp
• c/parallel.v2/src/hostjit/include/hostjit/codegen/cub_call.hpp
• c/parallel.v2/src/hostjit/include/hostjit/cuda_minimal/stubs/stdlib.h
• libcudacxx/include/cuda/std/__cccl/attributes.h
• libcudacxx/include/cuda/std/__cccl/visibility.h
• libcudacxx/include/cuda/std/__internal/features.h
• libcudacxx/include/cuda/std/cstdint

✅ Files skipped from review due to trivial changes (3)

• c/parallel.v2/src/hostjit/include/hostjit/codegen/cub_call.hpp
• c/parallel.v2/CMakeLists.txt
• c/parallel.v2/src/hostjit/include/hostjit/cuda_minimal/stubs/stdlib.h

🚧 Files skipped from review as they are similar to previous changes (1)

• c/parallel.v2/src/hostjit/compiler.cpp

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