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stdlib: map wchar_t to UInt16 on Windows #69105

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Merged
merged 1 commit into from
Oct 27, 2023
Merged

stdlib: map wchar_t to UInt16 on Windows #69105

merged 1 commit into from
Oct 27, 2023

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compnerd
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This is an ABI breaking change for Windows. WCHAR on Windows is mapped to short (-fshort-wchar makes it unsigned short). When C++ interop is enabled, WCHAR will be mapped to wchar_t which is then mapped to short (or unsigned short if -fshort-wchar is specified). Correct the mapping type to get the desired behaviour.

@compnerd
stdlib: map wchar_t to UInt16 on Windows
0aba98e 
This is an ABI breaking change for Windows.  `WCHAR` on Windows is
mapped to `short` (`-fshort-wchar` makes it `unsigned short`).  When C++
interop is enabled, `WCHAR` will be mapped to `wchar_t` which is then
mapped to `short` (or `unsigned short` if `-fshort-wchar` is specified).
Correct the mapping type to get the desired behaviour.
@compnerd compnerd requested a review from a team as a code owner October 10, 2023 22:12
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@swift-ci please test

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@swift-ci please test Windows platform

@stephentyrone
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@compnerd is this already on main?

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@stephentyrone yeap!

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Can you link to the PR against main here, please?

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@stephentyrone #68397

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This is dependent on #69328

@compnerd compnerd requested review from hyp and DougGregor October 25, 2023 16:53
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Explanation: Adjust the mapping for CWideChar for Windows. Windows uses UTF-16 for unicode string representation, not UTF-32. This corrects the mapping which fixes a number of issues with Windows API calls.
Scope: This is an ABI breaking change on Windows, the other platforms are not impacted by the change as they use UTF-32.
Issue:
Risk: This would require testing for Windows to ensure that the tests do not regress.
Testing: Validated that we can now import functions that use wchar_t on Windows with C++ interop, ran through the unit tests. This change has been on main for a while now as well and has been tested with larger code bases.
Reviewer: @DougGregor

DougGregor
DougGregor approved these changes Oct 26, 2023
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Looks good! This is something we should probably note in the ChangeLog, since it's going to have an impact on Windows users

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@swift-ci please test Windows platform

@compnerd compnerd merged commit 0ba5de9 into swiftlang:release/5.10 Oct 27, 2023
@compnerd compnerd deleted the wchar branch October 27, 2023 16:01
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@glessard glessard glessard approved these changes

@DougGregor DougGregor DougGregor approved these changes

@egorzhdan egorzhdan egorzhdan approved these changes

@hyp hyp Awaiting requested review from hyp

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@compnerd @stephentyrone @glessard @DougGregor @egorzhdan