Embarcadero的docwiki页面LLVM-based Delphi Compilers列出了Delphi XE8中的几种语言更改。其中一颗子弹说:



实际上这是什么意思?在Delphi XE7中曾经使用过哪些与指针相关的东西,而在Delphi XE8中不再使用那些与指针相关的东西?我似乎无法在Embarcadero的网站上找到对此的深入解释。例如,据说页面Migrating Delphi Code to Mobile from Desktop包含更多信息,但未提及单词“指针”。

最佳答案



那一定是文档中的错误。只需看一下RTL。使用指针很厚。

例如,CompareMem怎么样。定义如下:

function CompareMem(P1, P2: Pointer; Length: Integer): Boolean;

实现的运行方式如下:
function CompareMem(P1, P2: Pointer; Length: Integer): Boolean;
{$IF defined(POSIX)}
begin
  if Length <= 0 then
    Result := True
  else
    Result := memcmp(P1^, P2^, Length) = 0;
end;
{$ELSEIF defined(PUREPASCAL)}
....
{$ENDIF !PUREPASCAL}
POSIX代码由移动目标使用。

或如下所示的TObject怎么样:
type
  TObject = class
  public
    constructor Create;
    procedure Free;
    procedure DisposeOf; {$IFNDEF AUTOREFCOUNT} inline; {$ENDIF}
    class function InitInstance(Instance: Pointer): TObject {$IFDEF AUTOREFCOUNT} unsafe {$ENDIF};
    procedure CleanupInstance;
    function ClassType: TClass; inline;
    class function ClassName: string;
    class function ClassNameIs(const Name: string): Boolean;
    class function ClassParent: TClass;
    class function ClassInfo: Pointer; inline;
    class function InstanceSize: Integer; inline;
    class function InheritsFrom(AClass: TClass): Boolean;
    class function MethodAddress(const Name: _ShortStr): Pointer; overload;
    class function MethodAddress(const Name: string): Pointer; overload;
    class function MethodName(Address: Pointer): string;
    class function QualifiedClassName: string;
    function FieldAddress(const Name: _ShortStr): Pointer; overload;
    function FieldAddress(const Name: string): Pointer; overload;
    function GetInterface(const IID: TGUID; out Obj): Boolean;
    class function GetInterfaceEntry(const IID: TGUID): PInterfaceEntry;
    class function GetInterfaceTable: PInterfaceTable;
    class function UnitName: string;
    class function UnitScope: string;
{$IFDEF AUTOREFCOUNT}
    function __ObjAddRef: Integer; virtual;
    function __ObjRelease: Integer; virtual;
{$ENDIF}
    function Equals(Obj: TObject): Boolean; virtual;
    function GetHashCode: Integer; virtual;
    function ToString: string; virtual;
    function SafeCallException(ExceptObject: TObject;
      ExceptAddr: Pointer): HResult; virtual;
    procedure AfterConstruction; virtual;
    procedure BeforeDestruction; virtual;
    procedure Dispatch(var Message); virtual;
    procedure DefaultHandler(var Message); virtual;
    class function NewInstance: TObject {$IFDEF AUTOREFCOUNT} unsafe {$ENDIF}; virtual;
    procedure FreeInstance; virtual;
{$IFDEF AUTOREFCOUNT}
  protected
{$ENDIF}
    destructor Destroy; virtual;

{$IFDEF CPP_ABI_SUPPORT}
    procedure CPP_ABI_1; virtual;
    procedure CPP_ABI_2; virtual;
    procedure CPP_ABI_3; virtual;
{$ENDIF !CPP_ABI_SUPPORT}

  protected
    function GetDisposed: Boolean; inline;
    procedure CheckDisposed; {$IFNDEF AUTOREFCOUNT} inline; {$ENDIF}

{$IFDEF AUTOREFCOUNT}
  private const
    objDestroyingFlag = Integer($80000000);
    objDisposedFlag = Integer($40000000);
  protected
    [Volatile] FRefCount: Integer;
    class procedure __MarkDestroying(const Obj); static; inline;
    class function __SetDisposed(const Obj): Boolean; static; inline;
  public
    property RefCount: Integer read FRefCount;
{$ENDIF}
    property Disposed: Boolean read GetDisposed;
  end;

很明显,在移动平台上使用了指针。

阅读有关以下主题的Embarcadero白皮书:The Delphi Language for Mobile Development。同样,它涵盖了在多种情况下使用指针,并且很明显,它们也受支持。现在,不鼓励使用指针,如果可以轻易避免使用指针,那么也鼓励您这样做。但这与声明编译器不支持指针完全不同。

看起来至少有点讽刺意味的是,Embarcadero正在散布自己产品的FUD。

关于delphi - 在Delphi XE8的移动编译器中哪些指针相关的东西不起作用?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/31115037/

10-11 23:03
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