x/tools/gopls: SEGV reading through bad *types.Func pointer returned by Scope.Lookup

[adonovan]

#!stacks
"sigpanic" && "types.(*Func).Pkg:+0,+0x0" && "pushDecl"

Issue created by stacks.

More memory corruption.

This stack 1K4m2A was reported by telemetry:

• crash/crash
• runtime.throw:+9,+0x47
• runtime.sigpanic:+33,+0x26b
• go/types.(*Func).Pkg:+0,+0x0
• golang.org/x/tools/internal/gcimporter.(*iexporter).pushDecl:+3,+0x29
• golang.org/x/tools/internal/gcimporter.iexportCommon:+47,+0x908
• golang.org/x/tools/internal/gcimporter.IExportShallow:+8,+0x73
• golang.org/x/tools/gopls/internal/cache.storePackageResults:+9,+0x3c8
• golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).getPackage.func1.gowrap1:+0,+0x2b
• runtime.goexit:+0,+0x0

golang.org/x/tools/gopls@v0.21.0 go1.25.2 linux/amd64 gopls.client=other,vscode (1)

Use this command to reproduce the executable:
(HOME=$(mktemp -d); GOOS=linux GOARCH=amd64 GOTOOLCHAIN=go1.25.2 go install golang.org/x/tools/gopls@v0.21.0 && find $HOME/go/bin -type f)
To disassemble: go tool objdump exe | less

[gabyhelp]

Related Issues

• x/tools/gopls: SEGV loading m.used field from non-nil map pointer (in types.Scope.elems map) #76979
• x/tools/gopls: SEGV in (*types.*Checker).Ident due to nil or invalid *ast.Ident in syntax tree #77078
• x/tools/go/analysis/passes/unusedwrite: SEGV accessing go/ssa.Store.Attr field #77165
• x/tools/gopls: impossible panic in BlockStmt.End (type checking IfStmt with nil Body) #76327
• x/tools/gopls: SEGV accessing g in function prolog (R28 is nil or invalid) #76158
• x/tools/gopls: impossible panic reading rtype.hash in type assertion #76328
• x/tools/gopls: SEGV in gcimporter.iexportCommon (bad SP) #72135
• x/tools/gopls: bug in Codec[...].Encode #76978
• x/tools/gopls: impossible crash in (*types.Checker).basicLit #76329
• x/tools/gopls: nil (or invalid) *ExprStmt pointer in AST #76747

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