[win] Fix truncated unwinds for Arm64 Windows#153202
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rust-bors[bot] merged 1 commit intorust-lang:mainfrom Mar 8, 2026
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[win] Fix truncated unwinds for Arm64 Windows#153202rust-bors[bot] merged 1 commit intorust-lang:mainfrom
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I still wonder why we don't subtract 1 in backtrace-rs, as suggested in the issue, but I guess this change is still fine if other unwinders need it.
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| @@ -347,7 +347,13 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine( | |||
| // option causes bugs in the LLVM WebAssembly backend. You should be able to | |||
| // remove this check when Rust's minimum supported LLVM version is >= 18 | |||
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I suppose we could try wasm again now, but not in this PR of course...
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[win] Fix truncated unwinds for Arm64 Windows Panic backtraces on ARM64 Windows are truncated because Rust's LLVM configuration sets `NoTrapAfterNoreturn = true`, which suppresses the generation of `brk #0x1` (trap) instructions after calls to `noreturn` functions. Without this trap instruction, the return address from a `noreturn` call points past the end of the calling function into an unrelated function, causing `RtlLookupFunctionEntry` to return the wrong unwind information, which terminates the stack walk prematurely. In general, `NoTrapAfterNoreturn = true` is recommended against for Windows, since we have seen security vulnerabilities in the past where an attacker has managed to return from a noreturn function, or the function wasn't actually noereturn, resulting in executing whatever was after the call. This change disables setting `NoTrapAfterNoreturn = true` for Windows. Fixes rust-lang#140489
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Rollup of 4 pull requests Successful merges: - #153202 ([win] Fix truncated unwinds for Arm64 Windows) - #153437 (coretest in miri: fix using unstable libtest features) - #153446 (Always use the ThinLTO pipeline for pre-link optimizations) - #153548 (add test for closure precedence in `TokenStream`s)
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Rollup merge of #153202 - dpaoliello:arm64unwind, r=cuviper [win] Fix truncated unwinds for Arm64 Windows Panic backtraces on ARM64 Windows are truncated because Rust's LLVM configuration sets `NoTrapAfterNoreturn = true`, which suppresses the generation of `brk #0x1` (trap) instructions after calls to `noreturn` functions. Without this trap instruction, the return address from a `noreturn` call points past the end of the calling function into an unrelated function, causing `RtlLookupFunctionEntry` to return the wrong unwind information, which terminates the stack walk prematurely. In general, `NoTrapAfterNoreturn = true` is recommended against for Windows, since we have seen security vulnerabilities in the past where an attacker has managed to return from a noreturn function, or the function wasn't actually noereturn, resulting in executing whatever was after the call. This change disables setting `NoTrapAfterNoreturn = true` for Windows. Fixes #140489
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Panic backtraces on ARM64 Windows are truncated because Rust's LLVM configuration sets
NoTrapAfterNoreturn = true, which suppresses the generation ofbrk #0x1(trap) instructions after calls tonoreturnfunctions. Without this trap instruction, the return address from anoreturncall points past the end of the calling function into an unrelated function, causingRtlLookupFunctionEntryto return the wrong unwind information, which terminates the stack walk prematurely.In general,
NoTrapAfterNoreturn = trueis recommended against for Windows, since we have seen security vulnerabilities in the past where an attacker has managed to return from a noreturn function, or the function wasn't actually noereturn, resulting in executing whatever was after the call.This change disables setting
NoTrapAfterNoreturn = truefor Windows.Fixes #140489