runtime: make MemStats available to leaking collector

src/runtime/mstats_leaking.go

@@ -0,0 +1,18 @@
+//go:build gc.leaking
+// +build gc.leaking
+
+package runtime
+
+// ReadMemStats populates m with memory statistics.
+//
+// The returned memory statistics are up to date as of the
+// call to ReadMemStats. This would not do GC implicitly for you.
+func ReadMemStats(m *MemStats) {
+	m.HeapIdle = 0
+	m.HeapInuse = uint64(heapptr - heapStart)
+	m.HeapReleased = 0 // always 0, we don't currently release memory back to the OS.
+
+	m.HeapSys = m.HeapInuse + m.HeapIdle
+	m.GCSys = 0
+	m.Sys = uint64(heapEnd - heapStart)
+}