x/tools/gopls: nil deref in Exporter.ProcessEvent

[adonovan]

#!stacks
"sigpanic" && "metric.(*HistogramInt64Data).Handle:+0"

Issue created by stacks.

This stack TDQj4A was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• runtime.panicmem:=262
• runtime.sigpanic:+19
• golang.org/x/tools/internal/event/export/metric.(*HistogramInt64Data).Handle:+0
• golang.org/x/tools/internal/event/export/prometheus.(*Exporter).ProcessEvent.func1:+1
• sort.Search:+7
• golang.org/x/tools/internal/event/export/prometheus.(*Exporter).ProcessEvent:+12
• golang.org/x/tools/gopls/internal/debug.makeInstanceExporter.func1:+5
• golang.org/x/tools/gopls/internal/debug.makeInstanceExporter.StdTrace.func2:+30
• golang.org/x/tools/gopls/internal/debug.makeInstanceExporter.(*Config).Exporter.func3:+20
• golang.org/x/tools/gopls/internal/debug.makeInstanceExporter.Spans.func4:+30
• golang.org/x/tools/gopls/internal/debug.makeInstanceExporter.Labels.func5:+14
• golang.org/x/tools/gopls/internal/debug.init.0.makeGlobalExporter.func1:+23
• golang.org/x/tools/internal/event/core.deliver:+4
• golang.org/x/tools/internal/event/core.Export:=55
• golang.org/x/tools/internal/event.Metric:+1
• golang.org/x/tools/internal/jsonrpc2.(*conn).run:+23
• golang.org/x/tools/internal/jsonrpc2.(*conn).Go.gowrap1:+0

golang.org/x/tools/gopls@v0.17.1 go1.23.6 linux/amd64 vscode (1)

[gabyhelp]

Related Issues

• x/tools/gopls: Hover: nil deref in parseDocLink #70635 (closed)
• x/tools/internal/telemetry/export/metric: panic in (*HistogramFloat64Data).modify #38102 (closed)
• x/tools/gopls: Hover: nil deref in golang.StdSymbolOf #70969 (closed)
• x/tools/gopls: analysisinternal.ZeroValue crash on (presumably) unsafe.Pointer #70585 (closed)
• x/tools/gopls: Hover: invalid nil entry in types.Defs map #69362
• x/tools/gopls: "slice bounds out of range" crash in ExtractToNewFile #70553
• x/tools/gopls: OOB index crash in completion.expectedReturnStmtType #70636 (closed)
• x/tools/gopls: Rename: crash due to Info.Defs[id]=nil bug in checkStructField #70968
• x/tools/gopls: CodeAction: nil panic in findMatchingDiagnostics #71028 (closed)
• x/tools/gopls: stubmethods: nil deref of FuncType.Results in fromReturnStmt #70967 (closed)

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

[adonovan]

The panic is here:

func (data *HistogramInt64Data) Handle() string          { return data.Info.Name }

which means that either data is nil or data.Info is nil. The latter cannot be the case because the only place that HistogramInt64Data variables are constructed are this function:

func (info HistogramInt64) Record(e *Config, key *keys.Int64) {
	data := &HistogramInt64Data{Info: &info, key: key}
	e.subscribe(key, data.record)
}

which ensures that info is non-nil, and HistogramInt64Data.modify, which returns a non-nil data with a non-nil Info.

I also don't see any way a nil *HistogramInt64Data pointer can find its way into the prometheus.Exporter.metrics array.

Perhaps @ianthehat has ideas.