在XE5中,所有条件汇编如
{$IFDEF MSWINDOWS}
被替换
{$IF defined(MSWINDOWS)}
例如XE4中的System.Diagnostics.pas
...
implementation
{$IFDEF MSWINDOWS}
uses Winapi.Windows;
{$ENDIF}
{$IFDEF MACOS}
uses Macapi.Mach;
{$ENDIF}
{ TStopwatch }
...
现在在XE5它看起来像：
...
implementation
{$IF defined(MSWINDOWS)}
uses Winapi.Windows;
{$ELSEIF defined(MACOS)}
uses Macapi.Mach;
{$ELSEIF defined(POSIX)}
uses Posix.Time;
{$ENDIF}
{ TStopwatch }
...
有什么特别的原因我应该迁移我的类似的调用吗？
解决方法
根据Delphi文档：
http://docwiki.embarcadero.com/RADStudio/XE6/en/Conditional_compilation_%28Delphi%29
The conditional directives {$IFDEF},{$IFNDEF},{$IF},{$ELSEIF},{$ELSE},{$ENDIF},and {$IFEND} allow you to compile or suppress code based on the status of a conditional symbol.
{$IFDEF}和{$IFNDEF}只允许您使用{$DEFINE …}之前设置的定义.
然而,{$IF ..}指令更加灵活,因为：
Delphi identifiers cannot be referenced in any conditional directives other than {$IF} and {$ELSEIF}.
const LibVersion = 6; //One constant to define the libversion.
{$IF LibVersion >= 10.0}
do stuff that covers LibVersion 10,11 and 12
{$ELSEIF Libversion > 5.0}
do other stuff that covers LibVersion 6,7,8,9
{$IFEND}
如果你试图用定义做到这一点,你必须这样做
{$DEFINE Lib1}
{$DEFINE Lib2}
{$DEFINE Lib3}
{$DEFINE Lib4}
{$DEFINE Lib5}
{$DEFINE Lib6} //all prevIoUs versions have to be defined.
{$IFDEF Lib10}
do stuff that covers LibVersion 10,11 and 12
{$ELSE}
{$IFDEF Lib6}
do stuff that covers LibVersion 6,9
{$ENDIF}
{$ENDIF}
这只是一个稍微更高级的处理定义的版本.
{$IF ..}符号更强大,它允许您查询常量表达式,而不仅仅是定义.
{$IF ..}指令在Delphi 6中引入.
我猜Embarcadero决定清理代码库.