[SR-11170] SyntaxRewriter visitation exhausts the stack space that dispatch threads get

[tonyarnold]

Previous ID	SR-11170
Radar	None
Original Reporter	@tonyarnold
Type	Bug
Status	Resolved
Resolution	Done

Environment

macOS 10.14.5, Xcode 11 beta 4

Additional Detail from JIRA

Votes	0
Component/s	swift-format, SwiftSyntax
Labels	Bug
Assignee	@ahoppen
Priority	Medium

md5: 1b490d131fc3f34c23c544d465e9bd6f

Issue Description:

I've been working on putting together an Xcode Source Editor Extension that will allow me to format code from within Xcode using the SwiftFormat library, however when I use essentially the same code to reformat the source as the command line `swift-format` utility, I get a crash in SwiftSyntax, as shown in the backtrace below:

* thread #​3, queue = 'com.apple.NSXPCConnection.user.16716', stop reason = EXC_BAD_ACCESS (code=2, address=0x70000b360ff8)
    frame #&#8203;0: 0x00000001087ac09b SwiftFormatter`initializeBufferWithCopyOfBuffer for IdentifierPatternSyntax at <compiler-generated>:0
    frame #&#8203;1: 0x0000000108311bf8 SwiftFormatter`outlined init with copy of SyntaxData at <compiler-generated>:0
  * frame #&#8203;2: 0x00000001084e47aa SwiftFormatter`makeSyntax(data=SwiftSyntax.SyntaxData @ 0x000070000b365370) at SyntaxKind.swift:456:15
    frame #&#8203;3: 0x00000001087d3698 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b365418, node=SwiftSyntax.IdentifierPatternSyntax @ 0x00007fea3ed0dbb0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:20
    frame #&#8203;4: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;5: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;6: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;7: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.IdentifierPatternSyntax @ 0x00007fea3ed0db60, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;8: 0x00000001087c275f SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.IdentifierPatternSyntax @ 0x000070000b36fc10, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:862:12
    frame #&#8203;9: 0x00000001087d1af4 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.IdentifierPatternSyntax @ 0x00007fea3ed0dae0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1155:37
    frame #&#8203;10: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b370568, node=SwiftSyntax.PatternBindingSyntax @ 0x00007fea3ed0da40, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;11: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;12: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;13: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;14: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.PatternBindingSyntax @ 0x00007fea3ed0d9f0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;15: 0x00000001087bb648 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.PatternBindingSyntax @ 0x000070000b3780e0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:486:12
    frame #&#8203;16: 0x00000001087cbb1a SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.PatternBindingSyntax @ 0x00007fea3ed0d7c0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1061:34
    frame #&#8203;17: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b37b658, node=SwiftSyntax.PatternBindingListSyntax @ 0x00007fea3ed0d720, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;18: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;19: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;20: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;21: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.PatternBindingListSyntax @ 0x00007fea3ed0d6d0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;22: 0x00000001087bb748 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.PatternBindingListSyntax @ 0x000070000b383238, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:490:12
    frame #&#8203;23: 0x00000001087cbbe2 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.PatternBindingListSyntax @ 0x00007fea3ed0d8d0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1062:38
    frame #&#8203;24: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b386748, node=SwiftSyntax.VariableDeclSyntax @ 0x00007fea3ed0d650, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;25: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;26: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;27: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;28: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.VariableDeclSyntax @ 0x00007fea3ed0d600, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;29: 0x00000001087bb85f SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.VariableDeclSyntax @ 0x000070000b38e3f0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:494:12
    frame #&#8203;30: 0x00000001087cbcaa SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.VariableDeclSyntax @ 0x00007fea3ed0d580, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1063:32
    frame #&#8203;31: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b391898, node=SwiftSyntax.MemberDeclListItemSyntax @ 0x00007fea3ed0d0f0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;32: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;33: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;34: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;35: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.MemberDeclListItemSyntax @ 0x00007fea3ed0d0a0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;36: 0x00000001087ba248 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclListItemSyntax @ 0x000070000b398c38, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:418:12
    frame #&#8203;37: 0x00000001087caa48 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclListItemSyntax @ 0x00007fea3ed0d050, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1044:38
    frame #&#8203;38: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b39c988, node=SwiftSyntax.MemberDeclListSyntax @ 0x00007fea3ed0cfb0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;39: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;40: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;41: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;42: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.MemberDeclListSyntax @ 0x00007fea3ed0d450, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;43: 0x00000001087ba148 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclListSyntax @ 0x000070000b3a3cc0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:414:12
    frame #&#8203;44: 0x00000001087ca980 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclListSyntax @ 0x00007fea3ed0d3d0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1043:34
    frame #&#8203;45: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b3a7a78, node=SwiftSyntax.MemberDeclBlockSyntax @ 0x00007fea3ed0c660, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;46: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;47: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;48: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;49: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.MemberDeclBlockSyntax @ 0x00007fea3ed0cea0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;50: 0x00000001087ba048 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclBlockSyntax @ 0x000070000b3aed48, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:410:12
    frame #&#8203;51: 0x00000001087ca8b8 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.MemberDeclBlockSyntax @ 0x00007fea3ed0d220, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1042:35
    frame #&#8203;52: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b3b2b68, node=SwiftSyntax.ClassDeclSyntax @ 0x00007fea3ed0c610, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;53: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;54: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;55: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;56: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.ClassDeclSyntax @ 0x00007fea3ed0c5c0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;57: 0x00000001087b9a5f SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.ClassDeclSyntax @ 0x000070000b3b9c58, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:394:12
    frame #&#8203;58: 0x00000001087ca33c SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.ClassDeclSyntax @ 0x00007fea3ed0c910, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1038:29
    frame #&#8203;59: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b3bdcb8, node=SwiftSyntax.CodeBlockItemSyntax @ 0x00007fea3ed0c870, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;60: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;61: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;62: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;63: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.CodeBlockItemSyntax @ 0x00007fea3ed0c7d0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;64: 0x00000001087b2ac8 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.CodeBlockItemSyntax @ 0x000070000b3c2248, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:46:12
    frame #&#8203;65: 0x00000001087c425d SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.CodeBlockItemSyntax @ 0x00007fea3ed0cb90, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:951:33
    frame #&#8203;66: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b3c8da8, node=SwiftSyntax.CodeBlockItemListSyntax @ 0x00007fea3ed0c570, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;67: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;68: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;69: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;70: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.CodeBlockItemListSyntax @ 0x00007fea3ed0c520, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;71: 0x00000001087b2bc8 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.CodeBlockItemListSyntax @ 0x000070000b3cd3a0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:50:12
    frame #&#8203;72: 0x00000001087c4325 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.CodeBlockItemListSyntax @ 0x00007fea3ed0c4d0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:952:37
    frame #&#8203;73: 0x00000001087d3761 SwiftFormatter`closure #&#8203;1 in SyntaxRewriter.visitChildren(n=(Swift.Optional<SwiftSyntax.RawSyntax>, SwiftSyntax.AbsoluteSyntaxInfo) @ 0x000070000b3d3e98, node=SwiftSyntax.SourceFileSyntax @ 0x00007fea3ed0bb80, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1182:14
    frame #&#8203;74: 0x00000001087d393d SwiftFormatter`thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;75: 0x00000001087d39b4 SwiftFormatter`partial apply for thunk for @callee_guaranteed (@guaranteed RawSyntax?, @unowned AbsoluteSyntaxInfo) -> (@owned RawSyntax?, @error @owned Error) at <compiler-generated>:0
    frame #&#8203;76: 0x00007fff639bdc23 libswiftCore.dylib`(extension in Swift):Swift.Sequence.map<A>((A.Element) throws -> A1) throws -> Swift.Array<A1> + 1331
    frame #&#8203;77: 0x00000001087d2ee4 SwiftFormatter`SyntaxRewriter.visitChildren(nodeS=SwiftSyntax.SourceFileSyntax @ 0x00007fea3ed0b8b0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1177:45
    frame #&#8203;78: 0x00000001087ba348 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.SourceFileSyntax @ 0x000070000b3db2a0, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:422:12
    frame #&#8203;79: 0x00000001087cab10 SwiftFormatter`SyntaxRewriter.visit(node=SwiftSyntax.SourceFileSyntax @ 0x00007fea3ed03420, self=0x00007fea3ed019c0) at SyntaxRewriter.swift:1045:30
    frame #&#8203;80: 0x00000001082cd468 SwiftFormatter`FormatPipeline.visit(node=SwiftSyntax.SourceFileSyntax @ 0x00007fea3ed060f0, self=SwiftFormat.FormatPipeline @ 0x000070000b3df878) at Pipelines+Generated.swift:280:48
    frame #&#8203;81: 0x00000001082cf54a SwiftFormatter`SwiftFormatter.format<Output>(syntax=SwiftSyntax.SourceFileSyntax @ 0x000070000b3e00d0, url=Foundation.URL @ 0x000070000b3dfb50, outputStream=<no summary available>, self=0x00007fea88a0b590) at SwiftFormatter.swift:79:38
    frame #&#8203;82: 0x00000001081be67c SwiftFormatter`FormatEntireFileCommand.perform(invocation=0x00007fea5ef00d80, completionHandler=0x00000001081bf360 SwiftFormatter`partial apply forwarder for reabstraction thunk helper from @escaping @callee_unowned @convention(block) (@unowned Swift.Optional<__C.NSError>) -> () to @escaping @callee_guaranteed (@guaranteed Swift.Optional<Swift.Error>) -> () at <compiler-generated>, self=0x00007fea5ef04230) at FormatEntireFileCommand.swift:27:27
    frame #&#8203;83: 0x00000001081bf2fb SwiftFormatter`@objc FormatEntireFileCommand.perform(with:completionHandler:) at <compiler-generated>:0
    frame #&#8203;84: 0x0000000109b80ba1 XcodeKit`-[_XCSourceEditorService performCommandInvocation:commandIdentifier:request:reply:] + 469
    frame #&#8203;85: 0x00007fff3a4b3efb Foundation`__NSXPCCONNECTION_IS_CALLING_OUT_TO_EXPORTED_OBJECT_S4__ + 12
    frame #&#8203;86: 0x00007fff3a458e7f Foundation`-[NSXPCConnection _decodeAndInvokeMessageWithEvent:flags:] + 2499
    frame #&#8203;87: 0x00007fff3a458253 Foundation`message_handler + 215
    frame #&#8203;88: 0x00007fff64350f08 libxpc.dylib`_xpc_connection_call_event_handler + 56
    frame #&#8203;89: 0x00007fff6434ee9e libxpc.dylib`_xpc_connection_mach_event + 933
    frame #&#8203;90: 0x00007fff640cf6dd libdispatch.dylib`_dispatch_client_callout4 + 9
    frame #&#8203;91: 0x00007fff640e40d6 libdispatch.dylib`_dispatch_mach_msg_invoke + 436
    frame #&#8203;92: 0x00007fff640d5792 libdispatch.dylib`_dispatch_lane_serial_drain + 268
    frame #&#8203;93: 0x00007fff640e4c19 libdispatch.dylib`_dispatch_mach_invoke + 481
    frame #&#8203;94: 0x00007fff640d5792 libdispatch.dylib`_dispatch_lane_serial_drain + 268
    frame #&#8203;95: 0x00007fff640d63c6 libdispatch.dylib`_dispatch_lane_invoke + 433
    frame #&#8203;96: 0x00007fff640de6ed libdispatch.dylib`_dispatch_workloop_worker_thread + 598
    frame #&#8203;97: 0x00007fff6430f611 libsystem_pthread.dylib`_pthread_wqthread + 421
    frame #&#8203;98: 0x00007fff6430f3fd libsystem_pthread.dylib`start_wqthread + 13

I've uploaded the current state of the project to https://github.com/tonyarnold/XcodeSwiftFormatter as a reproduction of this crash.

Please let me know if you'd like more detail on anything - I'm happy to help!

[akyrtzi]

The problem is that the `SyntaxRewriter` visitation exhausts the stack space that dispatch threads get. This can be reproduced from a command-line tool by doing the formatting call on a dispatch queue other than the main one.

To workaround this run the formatting transformation under a pthread thread (which you can customize its stack allocation).

[akyrtzi]

Reproducer from a command-line tool:

import Foundation
import SwiftFormat
import SwiftFormatConfiguration
import SwiftSyntax

func doit() throws {
    let configuration = Configuration()
    let formatter = SwiftFormatter(configuration: configuration)
    let syntax = try SyntaxParser.parse(URL(fileURLWithPath: "/path/to/swift/file.swift"))
    let dummyFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(UUID().uuidString + ".swift")
    var output = String()
    try formatter.format(syntax: syntax, assumingFileURL: dummyFileURL, to: &output)
    print(output)
}
let q = DispatchQueue(label: "queue")
q.async {
    try! doit()
}
sleep(1)

[akyrtzi]

Here's how to fix this using `Thread`:

let work = DispatchWorkItem {
    doFormatting()
}
let thread = Thread {
    work.perform()
}
thread.stackSize = 8 << 20 // 8 MB.
thread.start()
work.wait()

[tonyarnold]

That did the trick! Thanks so much for the workaround, @akyrtzi - it works really nicely now.

[ahoppen]

The root issue of this is being tackled in swiftlang/swift-syntax#147 Once it‘s merged, the workaround using Thread should not be necessary anymore.