swiftlang/swift

Build Debug versions of `swiftrt.o` (`swiftrtd.o`)

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#87,468 opened on Feb 24, 2026

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Windowsgood first issueruntime

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Description

Windows does not provide a stable ABI between debug and release mode. This requires that we provide a debug build of swiftrt.obj and adjust the driver to select the proper version of swiftrt.obj when linking. This should allow us to build in Debug configurations without running into _ITERATOR_DEBUG_LEVEL mismatches.

Contributor guide

Research direction
Investigate how the Swift build system handles debug vs release builds on Windows, focusing on the need for a separate swiftrt debug library and the driver modifications required.
Tech stack
swiftc
Domain
build systemtooling
Issue type
Chore
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
cbuild systemWindows
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30