`test-e2e\Basic\std_array.cpp` fails to compile in debug mode on Windows

[robertszafa]

Describe the bug

The compilation of the Basic\std_array.cpp SYCL E2E test fails because device code cannot find a function used in the debug version of MSVC's C++ library:

> clang++ -DWIN32 -D_WINDOWS -Werror --driver-mode=cl -fsycl test-e2e\Basic\std_array.cpp /Od /MDd /Zi /EHsc
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.44.35207
\include\array(531,9): error: SYCL kernel cannot call an undefined function without 
SYCL_EXTERNAL attribute
  531 |         _STL_VERIFY(_Pos < _Size, "array subscript out of range");
      |         ^
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.44.35207
      |         ^
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.44.35207\include\yva
ls.h(255,5): note: expanded from macro '_STL_REPORT_ERROR'
  255 |     _MSVC_STL_DOOM_FUNCTION(mesg)
      |     ^
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.44.35207\include\yva
ls.h(249,41): note: expanded from macro '_MSVC_STL_DOOM_FUNCTION'
  249 | #define _MSVC_STL_DOOM_FUNCTION(mesg) ::_invoke_watson(nullptr, nullptr, nullptr, 0, 0) 
      |                                         ^
C:\Program Files (x86)\Windows Kits\10\include\10.0.22621.0\ucrt\corecrt.h(375,23): note: '_invo
ke_watson' declared here
  375 | _ACRTIMP void __cdecl _invoke_watson(
      |                       ^
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.44.35207\include\arr
ay(529,39): note: called by 'operator[]'
  529 |     _NODISCARD _CONSTEXPR17 reference operator[](_In_range_(<, _Size) size_type _Pos) no
except /* strengthened */ {
      |                                       ^
1 error generated.

This is a known issue mentioned in the DPC++ release notes. Is someone working on fixing this already? If not, which option would be preferable for a fix?
a) Just fix the std_array E2E test by adding -D_ITERATOR_DEBUG_LEVEL=0 to its compilation command.
b) Add -D_ITERATOR_DEBUG_LEVEL=0 to the SYCL clang driver whenever a debug C++ library is used on Windows.

To reproduce

No response

Environment

No response

Additional context

No response

[aelovikov-intel]

What compiler did you use to reproduce? 6.2 or trunk?

[robertszafa]

6.2. Is this fixed on tip?

[aelovikov-intel]

I haven't tried myself, but the test is in tree and seems to be passing in CI:
https://github.com/intel/llvm/actions/runs/18928825688/job/54043225009

...

so I'd be rather surprised if it wasn't.

Also, JFYI, post commit jobs have artifacts with toolchain binaries for both Linux/Windows. We also have nightly packages at https://github.com/intel/llvm/releases. CI status for can be seen at https://github.com/intel/llvm/actions/workflows/sycl-nightly.yml.

[robertszafa]

Thanks for the pointers! I've also tested v6.3-rc1 on my local machine and the test passes. It seems that PR #19897 fixed the issue.

[AlexeySachkov]

To add some info here:

a) Just fix the std_array E2E test by adding -D_ITERATOR_DEBUG_LEVEL=0 to its compilation command.

We shouldn't do this, because the whole idea of a test is to check that std::array just works in device code. Of course, the test isn't exactly thorough and the SYCL spec does not require std::array to be supported, but that is something we would like to have that test is a start.

b) Add -D_ITERATOR_DEBUG_LEVEL=0 to the SYCL clang driver whenever a debug C++ library is used on Windows.

I believe that we had such customization in the clang-cl driver, but we removed in #18252. Mainly that happened because depending on MSVC version installed on a machine, it may result in compilation errors saying that this macro cannot be set because it is not supported anymore. Plus, it created inconsistencies in behavior between clang-cl and clang driver on Windows which also caused some confusion for users.

As such, our current strategy is to provide stubs for any MSVC library functions that may be used under the hood of their std::array implementation to make it work.