x/tools/gopls: SEGV accessing g in function prolog (R28 is nil or invalid)

[adonovan]

#!stacks
"sigpanic" && "encoding/gob.(*Decoder).decodeValue:+0,+0x0"

Issue created by stacks.

This stack XnTGJw was reported by telemetry:

• crash/crash
• runtime.throw:+9,+0x33
• runtime.sigpanic:+33,+0x213
• encoding/gob.(*Decoder).decodeValue:+0,+0x0
• encoding/gob.(*Decoder).recvType:+9,+0xeb
• encoding/gob.(*Decoder).decodeTypeSequence:+22,+0x6b
• encoding/gob.(*Decoder).DecodeValue:+14,+0x16b
• encoding/gob.(*Decoder).Decode:+11,+0xd7
• golang.org/x/tools/internal/facts.(*Decoder).Decode:+23,+0x10f
• golang.org/x/tools/gopls/internal/cache.(*action).exec:+55,+0x2cf
• golang.org/x/tools/gopls/internal/cache.execActions.func1.1:+2,+0x47
• sync.(*Once).doSlow:+5,+0xdf
• sync.(*Once).Do:=69,+0x73
• golang.org/x/tools/gopls/internal/cache.execActions.func1:+2,+0x44
• runtime.goexit:+0,+0x3

golang.org/x/tools/gopls@v0.20.0 go1.25.1 darwin/arm64 gopls.client=other,vscode (1)

Use this command to reproduce the executable:
(HOME=$(mktemp -d); GOOS=darwin GOARCH=arm64 GOTOOLCHAIN=go1.25.1 go install golang.org/x/tools/gopls@v0.20.0 && find $HOME/go/bin -type f)
To disassemble: go tool objdump exe | less

[gabyhelp]

Related Issues

• x/tools/gopls: SEGV in string comparison in mapaccess #76159
• x/tools/gopls: SEGV in json.Marshal #75740
• x/tools/gopls: growslice crashes while zeroing #74932
• x/tools/gopls: SEGV in prolog of metadata.Graph.Update (bad g or sp) #74256
• x/tools/gopls: DidChangeWatchedFiles: impossible crash in growslice #75465
• x/tools/gopls: corrupt g in printf.run #75232
• x/tools/gopls: SEGV in mapassign #75673
• x/tools/gopls: SEGV in gcimporter.iexportCommon (bad SP) #72135
• x/tools/gopls: SEGV accessing map[string]... #73387
• x/tools/gopls: objectpath: panic due to nil *types.Signature #75575

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