[lldb] [Windows] Lldb-dap crashes when trying to step over breakpoint

[ktraunmueller]

I have a swift-winrt based Windows desktop app.

Debugging works fine in the app executable, but when trying to step over (some, not all) breakpoints in other modules (see Package.swift below), the debugger crashes with

Assertion failed: Out.empty(), file D:\r\_work\swift-build\swift-build\SourceCache\llvm-project\llvm\lib\Support\ConvertUTFWrapper.cpp, line 85
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: E:\\Swift\\Toolchains\\0.0.0+Asserts\\usr\\bin\\lldb-dap.exe
Exception Code: 0x80000003
 #0 0x00007ff7caa94b10 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x64b10)
 #1 0x00007ffb5b47b030 (C:\WINDOWS\System32\ucrtbase.dll+0x7b030)
 #2 0x00007ffb5b47bc3c (C:\WINDOWS\System32\ucrtbase.dll+0x7bc3c)
 #3 0x00007ffb5b47d5d4 (C:\WINDOWS\System32\ucrtbase.dll+0x7d5d4)
 #4 0x00007ffb5b47cbe0 (C:\WINDOWS\System32\ucrtbase.dll+0x7cbe0)
 #5 0x00007ffb5b47d70c (C:\WINDOWS\System32\ucrtbase.dll+0x7d70c)
 #6 0x00007ffa86d13628 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\liblldb.dll+0xcd3628)
 #7 0x00007ffa86a94108 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\liblldb.dll+0xa54108)
 #8 0x00007ffa862fc978 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\liblldb.dll+0x2bc978)
 #9 0x00007ff7caa6bfa0 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x3bfa0)
#10 0x00007ff7caa520bc (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x220bc)
#11 0x00007ff7caa5be08 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x2be08)
#12 0x00007ff7caa5c220 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x2c220)
#13 0x00007ff7caa55240 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x25240)
#14 0x00007ff7caaa84e4 (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x784e4)
#15 0x00007ff7caaa857c (E:\Swift\Toolchains\0.0.0+Asserts\usr\bin\lldb-dap.exe+0x7857c)
#16 0x00007ffb5d4a8740 (C:\WINDOWS\System32\KERNEL32.DLL+0x8740)
#17 0x00007ffb600d0eb4 (C:\WINDOWS\SYSTEM32\ntdll.dll+0xd0eb4)

lldb command-line debugging is working fine, so it looks this is an issue in the toolchain's lldb-dap debug adapter, not some general problem with my debugger setup.

Sorry, I know this is very thin information, unfortunately I haven't found more clues on how to reproduce or narrow this down.

Environment:

• Windows 11 arm64
• VS Code with swiftlang.swift-vscode Version 2.0.2
• current TBC Swift toolchain

The app's Package.swift

// swift-tools-version: 6.2

import PackageDescription

let GUILinkerSettings: [LinkerSetting] = [
    .unsafeFlags(["-Xlinker", "/SUBSYSTEM:WINDOWS"], .when(configuration: .release)),
    // Update the entry point to point to the generated swift function, this lets us keep the same main method
    // for debug/release
    .unsafeFlags(["-Xlinker", "/ENTRY:mainCRTStartup"], .when(configuration: .release)),
]

let package = Package(
    name: "Compositor-Windows",
    products: [
        .executable(
            name: "Compositor",
            targets: ["Compositor"]),
    ],
    dependencies: [
        // .package(url: "https://github.com/ktraunmueller/swift-cwinrt", branch: "main"),
        // .package(url: "https://github.com/ktraunmueller/swift-uwp", branch: "main"),
        // .package(url: "https://github.com/ktraunmueller/swift-windowsfoundation", branch: "main"),
        // .package(url: "https://github.com/ktraunmueller/swift-windowsappsdk", branch: "main"),
        // .package(url: "https://github.com/ktraunmueller/swift-winui", branch: "main"),
        // .package(url: "https://github.com/ktraunmueller/swift-plugins", branch: "main")
        .package(path: "../../../winrt/swift-cwinrt"),
        .package(path: "../../../winrt/swift-uwp"),
        .package(path: "../../../winrt/swift-win2d"),
        .package(path: "../../../winrt/swift-windowsappsdk"),
        .package(path: "../../../winrt/swift-windowsfoundation"),
        .package(path: "../../../winrt/swift-winui"),
        .package(path: "../Core")
    ],
    targets: [
        .executableTarget(
            name: "Compositor",
            dependencies: [
                .product(name: "CompositorCore", package: "Core"),
                .product(name: "CWinRT", package: "swift-cwinrt"),
                .product(name: "UWP", package: "swift-uwp"),
                .product(name: "Win2D", package: "swift-win2d"),
                .product(name: "WinAppSDK", package: "swift-windowsappsdk"),
                .product(name: "WindowsFoundation", package: "swift-windowsfoundation"),
                .product(name: "WinUI", package: "swift-winui"),
            ],
            swiftSettings: [.interoperabilityMode(.Cxx)],
            linkerSettings: GUILinkerSettings
        ),
    ],
    swiftLanguageModes: [.v5]
)