delphi - ARC : is there a memory leak in TNetEncoding. 获取Base64Encoding？

Question

下面是TNetEncoding.GetBase64Encoding的Delphi原始源代码。但我怀疑万一AtomicCmpExchange(Pointer(FBase64Encoding), Pointer(LEncoding), nil) <> nil会出现内存泄漏

 TNetEncoding = class
  private
    class var
      FBase64Encoding: TNetEncoding;

与

class function TNetEncoding.GetBase64Encoding: TNetEncoding;
var
  LEncoding: TBase64Encoding;
begin
  if FBase64Encoding = nil then
  begin
    LEncoding := TBase64Encoding.Create;
    if AtomicCmpExchange(Pointer(FBase64Encoding), Pointer(LEncoding), nil) <> nil then
      LEncoding.Free;
{$IFDEF AUTOREFCOUNT}
    FBase64Encoding.__ObjAddRef;
{$ENDIF AUTOREFCOUNT}
  end;
  Result := FBase64Encoding;
end;

我认为应该写成:

class function TNetEncoding.GetBase64Encoding: TNetEncoding;
var
  LEncoding: TBase64Encoding;
begin
  if FBase64Encoding = nil then
  begin
    LEncoding := TBase64Encoding.Create;
    if AtomicCmpExchange(Pointer(FBase64Encoding), Pointer(LEncoding), nil) <> nil then
      LEncoding.Free
{$IFDEF AUTOREFCOUNT}
    !!!ELSE!!! FBase64Encoding.__ObjAddRef;
{$ENDIF AUTOREFCOUNT}
  end;
  Result := FBase64Encoding;
end;

我错了吗？

Answer 1

你是对的。当 if 语句计算结果为 true 时，代码失败。当发生这种情况时，另一个线程已设法首先分配单例，并且已经增加了引用计数。引用计数不应再次增加。

您应该提交错误报告。