DELPHI是怎么實現跨平台的？
首先跨平台必須要兼容原來的語法，以線程的臨界區對象為例：
TCriticalSection = class(TSynchroObject)
{$IFDEF POSIX}
private type
TCritSec = record
FSync: TObject;
procedure Initialize; inline;
procedure Free; inline;
procedure Enter; inline;
procedure Leave; inline;
function TryEnter: Boolean; inline;
end;
{$ENDIF POSIX}
protected
{$IFDEF MSWINDOWS}
FSection: TRTLCriticalSection;
{$ENDIF MSWINDOWS}
{$IFDEF POSIX}
FSection: TCritSec;
{$ENDIF POSIX}
public
constructor Create;
destructor Destroy; override;
procedure Acquire; override;
procedure Release; override;
function TryEnter: Boolean;
procedure Enter; inline;
procedure Leave; inline;
end;
可以看出，已經不單是原來的從WINDOWS OS臨界封裝，通過{$IFDEF POSIX}跨平台編譯開關，增加了跨平台的封裝。
下面再以線程類TThread為例：
TThread = class
private type
PSynchronizeRecord = ^TSynchronizeRecord;
TSynchronizeRecord = record
FThread: TObject;
FMethod: TThreadMethod;
FProcedure: TThreadProcedure;
FSynchronizeException: TObject;
end;
private class var
FProcessorCount: Integer;
private
FThreadID: TThreadID;
{$IF Defined(MSWINDOWS)}
FHandle: THandle platform;
{$ELSEIF Defined(POSIX)}
FCreateSuspendedMutex: pthread_mutex_t;
FInitialSuspendDone: Boolean;
{$ENDIF POSIX}
FStarted: Boolean;
FCreateSuspended: Boolean;
FTerminated: Boolean;
FSuspended: Boolean;
FFreeOnTerminate: Boolean;
FFinished: Boolean;
FReturnValue: Integer;
。。。。。。
也和臨界區類一樣用跨平台編譯開關封裝了跨平台代碼進來。
從上面的2個例子可以看出，DELPHI為了跨平台，對RTL進行了艱苦卓絕的巨大修改，這個工程無疑是浩大的。