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Fix ARM64EC build failures: LNK4279 POINT icall thunk mismatch with MFC #975

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Merged
stephenegriffin merged 2 commits into from
Jun 12, 2026
Merged

Fix ARM64EC build failures: LNK4279 POINT icall thunk mismatch with MFC #975

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d92c5eb
Initial plan
Copilot Jun 12, 2026
1d86955
Fix ARM64EC LNK4279 thunk mismatch for PtInRect and WindowFromPoint
Copilot Jun 12, 2026
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10 changes: 10 additions & 0 deletions Directory.Build.props
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Original file line number Diff line number Diff line change
Expand Up @@ -53,4 +53,14 @@
<CETCompat>false</CETCompat>
</Link>
</ItemDefinitionGroup>

<!-- Suppress LNK4279 for ARM64EC: the new MSVC toolset (14.51+) classifies POINT as an
integer (i8) icall thunk while pre-built MFC libs use a struct (m8) thunk.
Both thunks produce equivalent code for this trivially-copyable 8-byte struct,
so the mismatch is a diagnostic false-positive introduced by the ABI transition. -->
<ItemDefinitionGroup Condition="'$(Platform)' == 'ARM64EC'">
<Link>
<AdditionalOptions>/IGNORE:4279 %(AdditionalOptions)</AdditionalOptions>
</Link>
</ItemDefinitionGroup>
</Project>
11 changes: 8 additions & 3 deletions UI/Dialogs/Dialog.cpp
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Expand Up @@ -114,9 +114,14 @@ namespace dialog
rcCloseIcon.top,
rcCloseIcon.right,
rcCloseIcon.bottom);
if (PtInRect(&rcCloseIcon, pt)) ret = HTCLOSE;
if (PtInRect(&rcMaxIcon, pt)) ret = HTMAXBUTTON;
if (PtInRect(&rcMinIcon, pt)) ret = HTMINBUTTON;
// Inline point-in-rect check to avoid ARM64EC icall thunk mismatch (LNK4279)
// between our code and the pre-built MFC library for PtInRect(RECT*, POINT).
const auto ptInRect = [](const RECT& rc, POINT p) noexcept {
return p.x >= rc.left && p.x < rc.right && p.y >= rc.top && p.y < rc.bottom;
};
if (ptInRect(rcCloseIcon, pt)) ret = HTCLOSE;
if (ptInRect(rcMaxIcon, pt)) ret = HTMAXBUTTON;
if (ptInRect(rcMinIcon, pt)) ret = HTMINBUTTON;

output::DebugPrint(output::dbgLevel::UI, L"CheckButtons result: %ws\r\n", FormatHT(ret).c_str());

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