@二小姐

这个更加不明白,理应会崩溃死掉的,偏偏跑得很欢乐一点事都没有.
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics,
Vcl.Controls, System.SynCObjs, Vcl.Forms, Vcl.Dialogs, System.Threading,
Vcl.StdCtrls;
var
v: integer;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
Lck: TCriticalSection;
tasks: array of ITask;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
i: integer;
begin
SetLength(tasks, 100);
for i := Low(tasks) to High(tasks) do
begin
tasks[i] := TTask.Create(
procedure()
var
i, j: integer;
begin
for i := 1 to 50000000 do
begin
v := i; //并发给全局V赋值，但不会出错？
j := v; //并发读取v的值
if j > 0 then
begin
// sleep(1);
if TTaskStatus.Canceled = TTask.CurrentTask.Status then
begin
break;
end;
end;
end;
OutputDebugString('Thread Finished');
end);
tasks[i].Start;
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
var
i: integer;
begin
for i := Low(tasks) to High(tasks) do
begin
tasks[i].Cancel;
end;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Lck := TCriticalSection.Create; //根本用不上...
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
FreeAndNil(Lck);
end;
end.

1、没有写的话没问题
2、天知道属性在背后做了什么，没有保证，除非你查看了源码确认没问题
3、有问题，结果难以预料
4、同上

注意：有问题不等价于会崩溃死掉
你写的这代码，也就是出现会读到脏数据的问题，还不至于崩溃掉
你在j := v后再加句 if j <> i then OutputDebugString(PChar(i.ToString() + ',' + j.ToString()));看看不就一目了然

真那么想崩溃的话，试下这样：
var
t: string;
function MyThreadFun(p: Pointer): Integer; stdcall;
var
i: Integer;
begin
for i := 1 to 100000 do
begin
t := i.ToString();
end;
Result := 0;
end;
procedure TForm1.Button3Click(Sender: TObject);
var
ID: DWORD;
hThread: THandle;
begin
IsMultiThread := False;
hThread := CreateThread(nil, 0, @MyThreadFun, nil, CREATE_SUSPENDED, ID);
ResumeThread(hThread);
hThread := CreateThread(nil, 0, @MyThreadFun, nil, CREATE_SUSPENDED, ID);
ResumeThread(hThread);
hThread := CreateThread(nil, 0, @MyThreadFun, nil, CREATE_SUSPENDED, ID);
ResumeThread(hThread);
Button3.Enabled := False;
end;
分分钟秒崩，当然如果把IsMultiThread设置为true的话，一样死不了

好了,将v的类型从integer换为string,无论是将v作为独立公共变量还是对象里面的属性,都不会出错, Delphi真是碉堡了,...
SetLength(tasks, 150);
for i := Low(tasks) to High(tasks) do
begin
tasks[i] := TTask.Create(
procedure()
var
i, j: integer;
begin
for i := 1 to 500000000 do
begin
Form1.v := inttostr(i); // 并发给全局V赋值，但不会出错？
j := strtoint(Form1.v); // 并发读取v的值
if j <> i then
begin
// OutputDebugString(pchar(format('%d,%d',[j,i])));
end;
if TTaskStatus.Canceled = TTask.CurrentTask.Status then
begin
break;
end;
sleep(random(5));
end;
OutputDebugString('Thread Finished');
end);
tasks[i].Start;

用TThread.createanonymousThread来创建独立线程,也跑得挺好, @二小姐
这原子锁加得好,但如题要避免并发的IO操作就要自己加锁了.