关于指针初始化的问题 - 回复"下雨天2"

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

var
i1: Integer; {会被自动初始化为 0}
p1: Pointer; {会被自动初始化为 0, 也就是空指针}
const
BoolStr: array[Boolean] of string = ('False','True');

procedure TForm1.FormCreate(Sender: TObject);
var
i2: Integer; {会被初始化为一个随机值}
p2: Pointer; {会被初始化为一个随机地址}
b: Boolean;
begin
ShowMessage(IntToStr(i1));          {0}
ShowMessage(IntToStr(i2));          {14909552}
ShowMessage(IntToStr(Integer(p1))); {0}
ShowMessage(IntToStr(Integer(p2))); {4570636}

{判断 p1、p2 两个指针是否是已赋值}
b := Assigned(p1);
ShowMessage(BoolStr[b]);  {False}
b := Assigned(p2);
ShowMessage(BoolStr[b]);  {True}

{释放指针后再判断}
p1 := nil;
p2 := nil;
b := Assigned(p1);
ShowMessage(BoolStr[b]);  {False}
b := Assigned(p2);
ShowMessage(BoolStr[b]);  {False}
end;

end.