x/tools/gopls: SEGV in gcimporter.iexportCommon (bad SP)

[adonovan]

#!stacks
"sigpanic" && "gcimporter.(*iexporter).pushDecl:+0"

Issue created by stacks.

	for _, pkg := range pkgs {
		scope := pkg.Scope()
		for _, name := range scope.Names() {
			if token.IsExported(name) {
				p.pushDecl(scope.Lookup(name))  <---- in this call

func (p *iexporter) pushDecl(obj types.Object) { <---- SEGV
	// Package unsafe is known to the compiler and predeclared.
	// Caller should not ask us to do export it.
	if obj.Pkg() == types.Unsafe {

All memory-operand instructions on that source line are indicated by the comments below. None can fail unless the SP register or g (R14) is bad.

TEXT golang.org/x/tools/internal/gcimporter.(*iexporter).pushDecl(SB) /Users/adonovan/w/xtools/internal/gcimporter
/iexport.go
  iexport.go:654        0x16cd9c0               493b6610                CMPQ SP, 0x10(R14)	// load g.stackguard_00
  iexport.go:654        0x16cd9c4               0f86d4000000            JBE 0x16cda9e
  iexport.go:654        0x16cd9ca               55                      PUSHQ BP		// save FP
  iexport.go:654        0x16cd9cb               4889e5                  MOVQ SP, BP
  iexport.go:654        0x16cd9ce               4883ec18                SUBQ $0x18, SP
  ...
  iexport.go:654        0x16cd9d7               48895c2430              MOVQ BX, 0x30(SP)	// spill obj.t
  iexport.go:654        0x16cd9dc               48894c2438              MOVQ CX, 0x38(SP)	// spill obj.v

This stack R1nKxA was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• golang.org/x/tools/internal/gcimporter.iexportCommon.func1:+7
• runtime.gopanic:+50
• runtime.panicmem:=262
• runtime.sigpanic:+19
• golang.org/x/tools/internal/gcimporter.(*iexporter).pushDecl:+0
• golang.org/x/tools/internal/gcimporter.iexportCommon:+40
• golang.org/x/tools/internal/gcimporter.IExportShallow:+8
• golang.org/x/tools/gopls/internal/cache.storePackageResults:+9
• golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).getPackage.func1.gowrap1:+0
• runtime.goexit:+0

golang.org/x/tools/gopls@v0.17.1 go1.23.4 darwin/amd64 neovim,vscode (1)

[adonovan]

cc: @prattmic

[gabyhelp]

Related Issues

• x/tools/gopls: crash exporting constant with partially defined type #60891 (closed)
• runtime: SEGV in mapaccess2 (go1.23.2 darwin/amd64) #71123
• x/tools/gopls: getImportPackage crash (PackagePath == "unsafe", id != "unsafe") (Bazel?) #60890 (closed)
• x/tools/gopls: SEGV while clearing memory in newobject #71561
• x/tools/gopls: panic in aeshashbody on behalf of mapaccess2_faststr: string memory corrupted #71367
• x/tools/gopls/internal/regtest/workspace: unrecognized failures #59080 (closed)
• x/tools/gopls/internal/test/integration/misc: unrecognized failures #65862 (closed)
• x/tools/imports: panic in (*moduleResolver).scan #30292 (closed)
• x/tools/gopls: panic in internal/lsp/cache.typeCheckBatch.importMap #61512 (closed)
• x/tools/internal/imports: invalid memory address or nil pointer dereference (crash) #57622 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[mknyszek]

In triage, @prattmic suggests this is either a bad line number or it crashed in the prologue. Both of which are pretty bad scenarios.

[mknyszek]

I think we need more information, so possibly just more crashes.