delphi 下 用assert 来完成错误的捕捉

delphi 下用assert 来完成错误的捕捉

delphi 下用assert 来完成错误的捕捉

Assert 过程原形procedure Assert (expr :Boolean [; const msg: string]);在system.pas 里Assert 的实现是:

procedure _Assert(const Message, Filename: AnsiString; LineNumber: Integer);

{$IFDEF PUREPASCAL}

begin

if Assigned(AssertErrorProc) then

AssertErrorProc(Message, Filename, LineNumber, Pointer(-1)) else

Error(reAssertionFailed);

// loses return addressend;

{$ELSE}

asm PUSH EBX

{$IFDEF PIC}

PUSH EAX

PUSH ECX

CALL GetGOT

MOV EBX, EAX

MOV EAX, [EBX].

AssertErrorProc

CMP [EAX], 0

POP ECX POP EAX

{$ELSE}

CMP AssertErrorProc,0{$ENDIF} JNZ @@1

MOV AL,reAssertionFailed

CALL Error

JMP @@exit

@@1: PUSH [ESP+4].Pointer

{$IFDEF PIC}

MOV EBX, [EBX].AssertErrorProc

CALL [EBX]

{$ELSE}

CALL AssertErrorProc

{$ENDIF}

@@exit: POP EBX

end;

{$ENDIF}

可以看出AssertErrorProc() 是没有初值的,通过对其赋值可以定义自己的Assert处理过程,

另如果未对AssertErrorProc赋值,将调用Error()处理过程来做为异常处理.

TAssertErrorProc = procedure (const Message, Filename: string; LineNumber: Integer; ErrorAddr: Pointer);

{$ASSERTIONS OFF/ON} 开关来决定Assert是否被调用. 可以在project-option-complier里设置.

这样就可以在beta或debug版本是打开,而最终发布时关闭调试输出了.

一个简单的AssertErrorProc 例程:

unit AssertLogs;

interface

implementation

uses

Windows,

SysUtils;

var

runErrMsg : String;

oldAssertErrorProc : TAssertErrorProc;

procedure LogAssert(const Message, Filename: string; LineNumber: Integer; ErrorAddr: Pointer);

begin

runErrMsg := format('Error: %s, Addr: %p, in file(%d): %s ', [Message, ErrorAddr, LineNumber, FileName]);

if IsConsole then

Writeln(runErrMsg)

else

MessageBox(0, pChar(runErrMsg), 'Error Log by AssertLogs', 0);

end;

initialization

oldAssertErrorProc := AssertErrorProc;

AssertErrorProc := @LogAssert;

finalization

AssertErrorProc := oldAssertErrorProc;

end.

************************************* 那么在output debug信息时只需要: Assert(false,outputstring);