From 23397701ff1ad787e0a2852720fb5aa38495f50f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan-Otto=20Kr=C3=B6pke?= <mail@jkroepke.de>
Date: Fri, 20 Mar 2026 20:27:02 +0100
Subject: [PATCH] pdh/registry: fix panic when T is a struct type (#2366)
 (#2367)

Co-authored-by: Kayla Ondracek <112117836+kondracek-nr@users.noreply.github.com>
---
 internal/pdh/registry/collector.go    |  2 +-
 internal/pdh/registry/perflib_test.go | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/internal/pdh/registry/collector.go b/internal/pdh/registry/collector.go
index a868e977..f4200f74 100644
--- a/internal/pdh/registry/collector.go
+++ b/internal/pdh/registry/collector.go
@@ -53,7 +53,7 @@ func NewCollector[T any](object string, _ []string) (*Collector, error) {
 		counters:       make(map[string]Counter),
 	}
 
-	valueType := reflect.TypeFor[T]().Elem()
+	valueType := reflect.TypeFor[T]()
 
 	if f, ok := valueType.FieldByName("Name"); ok {
 		if f.Type.Kind() == reflect.String {
diff --git a/internal/pdh/registry/perflib_test.go b/internal/pdh/registry/perflib_test.go
index ecc74359..c3340b4d 100644
--- a/internal/pdh/registry/perflib_test.go
+++ b/internal/pdh/registry/perflib_test.go
@@ -21,6 +21,22 @@ import (
 	"testing"
 )
 
+// TestNewCollectorStructTypeParam guards against a regression where
+// reflect.TypeFor[T]().Elem() panicked when T is a plain struct (not a pointer).
+// See https://github.com/prometheus-community/windows_exporter/issues/2365
+func TestNewCollectorStructTypeParam(t *testing.T) {
+	type systemCounterValues struct {
+		Name string
+
+		ProcessorQueueLength float64 `perfdata:"Processor Queue Length"`
+	}
+
+	_, err := NewCollector[systemCounterValues]("System", nil)
+	if err != nil {
+		t.Skipf("skipping: failed to create collector: %v", err)
+	}
+}
+
 func BenchmarkQueryPerformanceData(b *testing.B) {
 	for b.Loop() {
 		_, _ = QueryPerformanceData("Global", "")