Harden Windows macros against dangling-else ambiguity

[Eamon (Eamon2009)]

Summary of the Pull Request

Hardens EMIT_USER_WARNING and THROW_HR_WITH_USER_ERROR_IF in src/windows/common/ExecutionContext.h by wrapping them in do { ... } while (false) statement wrappers. This is the Windows counterpart to the Linux fix in #41504.

PR Checklist

• Closes: Fixes dangling-else vulnerability on Windows (follow-up to Fix dangling-else bugs in FAIL_FAST_IF and EMIT_USER_WARNING macros #41504)
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

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Detailed Description of the Pull Request / Additional comments

Both EMIT_USER_WARNING and THROW_HR_WITH_USER_ERROR_IF were defined as bare if statements, leaving Windows callers vulnerable to dangling-else misassociation when the macros are used without braces:

if (condition)
    EMIT_USER_WARNING(L"msg");
else
    // This else incorrectly binds to the macro's inner if

This change wraps both macros in do { ... } while (false) so they always expand to a single statement. This brings the Windows header into parity with the already-hardened Linux definition from #41504 and prevents the outer else from binding to the inner if generated by the macro.

Validation Steps Performed

• Verified that EMIT_USER_WARNING and THROW_HR_WITH_USER_ERROR_IF now expand to single statements when used in if/else contexts without braces.
• Reviewed the Linux counterpart (Fix dangling-else bugs in FAIL_FAST_IF and EMIT_USER_WARNING macros #41504) to ensure consistency between platforms.

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[Copilot]

🟡 Changes recommended

The new do { ... } while (false) macro expansions are missing the trailing semicolons, making them inconsistent with other macros in the header and potentially breaking existing call sites that omitted ; previously.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR hardens Windows-side user warning / user-error helper macros in ExecutionContext.h by wrapping them in do { ... } while (false) so they behave as a single statement and avoid dangling-else misassociation in if/else constructs.

Changes:

• Wrap THROW_HR_WITH_USER_ERROR_IF in a do { ... } while (false) guard.
• Wrap EMIT_USER_WARNING in a do { ... } while (false) guard.

File summaries

File	Description
src/windows/common/ExecutionContext.h	Wrapes the two macros in do { ... } while (false) to prevent dangling-else ambiguity in caller code.

Review details

Suppressed comments (1)

src/windows/common/ExecutionContext.h:47

• This do { ... } while (false) wrapper is missing the trailing semicolon. Adding it makes the macro a complete statement (matching other macros in this header) and avoids forcing all call sites to include a trailing ; where the previous if (...) { ... } form did not require one.

#define EMIT_USER_WARNING(Warning) \
    do \
    { \
        if (::wsl::windows::common::ExecutionContext* context = ::wsl::windows::common::ExecutionContext::Current(); context != nullptr) \
        { \
            context->EmitUserWarning(Warning); \
        } \
    } while (false)

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🟢 Approval recommended

The change is a small, well-scoped macro hardening that preserves behavior while eliminating a confirmed control-flow ambiguity.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0 new
• Review effort level: Lite

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[Ben Hillis (benhillis)]

/azp run

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Successfully started running 1 pipeline(s).

[Ben Hillis (benhillis)]

Change looks good to me, thank you for the contribution!