我在 Delphi 中遇到了线程如何工作以及为什么在线程应该引发异常的时候,却没有显示异常的困境。下面是带有注释的代码,也许有人可以向我解释一下该线程或 Delphi 如何处理访问冲突。
//线程代码
unit Unit2;
interface
uses
Classes,
Dialogs,
SysUtils,
StdCtrls;
type
TTest = class(TThread)
private
protected
j: Integer;
procedure Execute; override;
procedure setNr;
public
aBtn: tbutton;
end;
implementation
{ TTest }
procedure TTest.Execute;
var
i : Integer;
a : TStringList;
begin
// make severals operations only for having something to do
j := 0;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
for i := 0 to 100000000 do
j := j + 1;
Synchronize(setnr);
a[2] := 'dbwdbkbckbk'; //this should raise an AV!!!!!!
end;
procedure TTest.setNr;
begin
aBtn.Caption := IntToStr(j)
end;
end.
项目的代码unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs,
Unit2, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
public
nrthd:Integer;
acrit:TRTLCriticalSection;
procedure bla();
procedure bla1();
function bla2():boolean;
procedure onterm(Sender:TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.bla;
begin
try
bla1;
except on e:Exception do
ShowMessage('bla '+e.Message);
end;
end;
procedure TForm1.bla1;
begin
try
bla2
except on e:Exception do
ShowMessage('bla1 '+e.Message);
end;
end;
function TForm1.bla2: boolean;
var ath:TTest;
begin
try
ath:=TTest.Create(true);
InterlockedIncrement(nrthd);
ath.FreeOnTerminate:=True;
ath.aBtn:=Button1;
ath.OnTerminate:=onterm;
ath.Resume;
except on e:Exception do
ShowMessage('bla2 '+e.Message);
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
//
try
bla;
while nrthd>0 do
Application.ProcessMessages;
except on e:Exception do
ShowMessage('Button1Click '+e.Message);
end;
ShowMessage('done with this');
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
nrthd:=0;
end;
procedure TForm1.onterm(Sender: TObject);
begin
InterlockedDecrement(nrthd)
end;
end.
这个应用程序的目的仅是为了知道访问冲突在哪里被捕获,并且如何编写代码。
我不理解为什么在“a [2]:= 'dbwdbkbckbk';”这一行中不会引发访问冲突。