Reference/!ifmacrodef

!ifmacrodef

gflag [bcheck gflag [...]]]

This command, when paired with an !endif command, will tell the compiler whether or not to compile the lines in between the two lines. If the macro gflag exists, then the contained lines will be compiled. Otherwise, they will be skipped. 'bcheck' can be specified as & (boolean and) or | (boolean or) along with more gflags -- precedence is simple, left to right.

!macro SomeMacro
!macroend
!ifmacrodef SomeMacro
  !echo "SomeMacro is defined"
!endif

Command introduced with NSIS v2.0