[🍒 release/6.1.1] [lldb] Clear thread name container before writing UTF8 bytes (#134150) #10696
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…4150) `llvm::convertUTF16ToUTF8String` opens with an assertion that the output container is empty: https://github.com/llvm/llvm-project/blob/3bdf9a08804a5b424fd32fef3b0089f3a6db839d/llvm/lib/Support/ConvertUTFWrapper.cpp#L83-L84 It's not clear to me why this function requires the output container to be empty instead of just overwriting it, but the callsite in `TargetThreadWindows::GetName` may reuse the container without clearing it out first, resulting in an assertion failure: ``` # Child-SP RetAddr Call Site 00 000000d2`44b8ea48 00007ff8`beefc12e ntdll!NtTerminateProcess+0x14 01 000000d2`44b8ea50 00007ff8`bcf518ab ntdll!RtlExitUserProcess+0x11e 02 000000d2`44b8ea80 00007ff8`bc0e0143 KERNEL32!ExitProcessImplementation+0xb 03 000000d2`44b8eab0 00007ff8`bc0e4c49 ucrtbase!common_exit+0xc7 04 000000d2`44b8eb10 00007ff8`bc102ae6 ucrtbase!abort+0x69 05 000000d2`44b8eb40 00007ff8`bc102cc1 ucrtbase!common_assert_to_stderr<wchar_t>+0x6e 06 000000d2`44b8eb80 00007fff`b8e27a80 ucrtbase!wassert+0x71 07 000000d2`44b8ebb0 00007fff`b8b821e1 liblldb!llvm::convertUTF16ToUTF8String+0x30 [D:\r\_work\swift-build\swift-build\SourceCache\llvm-project\llvm\lib\Support\ConvertUTFWrapper.cpp @ 88] 08 000000d2`44b8ec30 00007fff`b83e9aa2 liblldb!lldb_private::TargetThreadWindows::GetName+0x1b1 [D:\r\_work\swift-build\swift-build\SourceCache\llvm-project\lldb\source\Plugins\Process\Windows\Common\TargetThreadWindows.cpp @ 198] 09 000000d2`44b8eca0 00007ff7`2a3c3c14 liblldb!lldb::SBThread::GetName+0x102 [D:\r\_work\swift-build\swift-build\SourceCache\llvm-project\lldb\source\API\SBThread.cpp @ 432] 0a 000000d2`44b8ed70 00007ff7`2a3a5ac6 lldb_dap!lldb_dap::CreateThread+0x1f4 [S:\SourceCache\llvm-project\lldb\tools\lldb-dap\JSONUtils.cpp @ 877] 0b 000000d2`44b8ef10 00007ff7`2a3b0ab5 lldb_dap!`anonymous namespace'::request_threads+0xa6 [S:\SourceCache\llvm-project\lldb\tools\lldb-dap\lldb-dap.cpp @ 3906] 0c 000000d2`44b8f010 00007ff7`2a3b0fe8 lldb_dap!lldb_dap::DAP::HandleObject+0x1c5 [S:\SourceCache\llvm-project\lldb\tools\lldb-dap\DAP.cpp @ 796] 0d 000000d2`44b8f130 00007ff7`2a3a8b96 lldb_dap!lldb_dap::DAP::Loop+0x78 [S:\SourceCache\llvm-project\lldb\tools\lldb-dap\DAP.cpp @ 812] 0e 000000d2`44b8f1d0 00007ff7`2a4b5fbc lldb_dap!main+0x1096 [S:\SourceCache\llvm-project\lldb\tools\lldb-dap\lldb-dap.cpp @ 5319] 0f (Inline Function) --------`-------- lldb_dap!invoke_main+0x22 [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl @ 78] 10 000000d2`44b8fb80 00007ff8`bcf3e8d7 lldb_dap!__scrt_common_main_seh+0x10c [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl @ 288] 11 000000d2`44b8fbc0 00007ff8`beefbf6c KERNEL32!BaseThreadInitThunk+0x17 12 000000d2`44b8fbf0 00000000`00000000 ntdll!RtlUserThreadStart+0x2c ``` This stack trace was captured from the lldb distributed in the Swift toolchain. The issue is easy to reproduce by resuming from a breakpoint twice in VS Code. I've verified that clearing out the container here fixes the assertion failure. (cherry picked from commit be3abfc)
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Some folks ran into this bug on the 6.1 release, so backport the fix to 6.1.1 while we can: https://forums.swift.org/t/lldb-crashes-during-vs-code-debug-session-on-windows-10/79902 cc @compnerd |
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@swift-ci please test |
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CC: @bnbarham @shahmishal |
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Explanation:
Clear out the thread name container before refilling it to avoid triggering an assertion that the target string container is empty in
llvm::convertUTF16ToUTF8String.Scope:
This change is trivial. Either the string container was already empty, in which case clearing it does nothing, or it was not empty, in which case clearing it prevents a crash.
Issues:
[lldb] [Windows] Lldb-dap crashes when trying to step over breakpoint llvm/llvm-project#133904
Original PRs:
[lldb] Clear thread name container before writing UTF8 bytes llvm/llvm-project#134150
Risk:
Very low risk. This code is Windows only and the change is small, easy to understand, and fixes a known crash that has been observed by users.
Testing:
No additional testing on this release specifically, but the fix has been verified externally: https://forums.swift.org/t/lldb-crashes-during-vs-code-debug-session-on-windows-10/79902/3
Reviewers:
@compnerd
(cherry picked from commit be3abfc)