Initial commit

vendor/github.com/cockroachdb/pebble/internal/cache/value_invariants.go

@@ -0,0 +1,55 @@
+// Copyright 2020 The LevelDB-Go and Pebble Authors. All rights reserved. Use
+// of this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+
+//go:build (invariants && !race) || (tracing && !race)
+// +build invariants,!race tracing,!race
+
+package cache
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/cockroachdb/pebble/internal/invariants"
+	"github.com/cockroachdb/pebble/internal/manual"
+)
+
+// newValue creates a Value with a manually managed buffer of size n.
+//
+// This definition of newValue is used when either the "invariants" or
+// "tracing" build tags are specified. It hooks up a finalizer to the returned
+// Value that checks for memory leaks when the GC determines the Value is no
+// longer reachable.
+func newValue(n int) *Value {
+	if n == 0 {
+		return nil
+	}
+	b := manual.New(n)
+	v := &Value{buf: b}
+	v.ref.init(1)
+	// Note: this is a no-op if invariants and tracing are disabled or race is
+	// enabled.
+	invariants.SetFinalizer(v, func(obj interface{}) {
+		v := obj.(*Value)
+		if v.buf != nil {
+			fmt.Fprintf(os.Stderr, "%p: cache value was not freed: refs=%d\n%s",
+				v, v.refs(), v.ref.traces())
+			os.Exit(1)
+		}
+	})
+	return v
+}
+
+func (v *Value) free() {
+	// When "invariants" are enabled set the value contents to 0xff in order to
+	// cache use-after-free bugs.
+	for i := range v.buf {
+		v.buf[i] = 0xff
+	}
+	manual.Free(v.buf)
+	// Setting Value.buf to nil is needed for correctness of the leak checking
+	// that is performed when the "invariants" or "tracing" build tags are
+	// enabled.
+	v.buf = nil
+}