Syntax:
#IFDEF name
Lines following #IFDEF are read only if the keyword name following it is defined.
They are read until the keywords #ELSE or #ENDIF are encountered, after which normal processing is resumed.
Example :
#IFDEF VER2_6_0 -Fu/usr/lib/fpc/2.6.0/linuxunits #ENDIF
In the above example, /usr/lib/fpc/2.6.0/linuxunits will be added to the path if you’re compiling with version 2.6.0 of the compiler.