test if a variable is empty and give default value during qmake

qmake, qt

Solution

there is already the function isEmpty I didn't spot:

isEmpty(VARIABLE){
  VARIABLE = test
}    
isEmpty(VARIABLE ){
  message(variable is empty)
}

I don't understand why eval didnt work thought...

Problem

How can you test if a variable is empty or not defined in a `qmake` `.pro` file? I want to be able to set up a default value if the variable is not defined. I tried ``` eval("VARIABLE" = ""){ VARIABLE = test } eval("VARIABLE" = ""){ message(variable is empty) } ``` but I still get the message "variable is empty".

Original source