conditional compiling

wenbinyu · ‎05-20-2022

I am interested in using conditional compiling using ifort. I have the following simple code with name test.f90

program ConditionalCompiling
implicit none

#IFDEF Flag
write(*,*)"Compiled with Flag defined"
#ELIF
write(*,*)"Not Compiled with Flag defined or compiled with Flag not defined"
#ENDIF
end program ConditionalCompiling

However, when I use ifort -c test.f90. It gives me the following message. Can you help me to get it compiled and behave as expected? Thanks a lot!

test.F90(4): warning #5117: Bad # preprocessor line
#IFDEF Flag
-^
test.F90(6): warning #5117: Bad # preprocessor line
#ELIF
-^
test.F90(8): warning #5117: Bad # preprocessor line
#ENDIF
-^

Steve_Lionel · ‎05-20-2022

Add the -fpp switch.

wenbinyu · ‎05-20-2022

Steve, thanks a lot for your quick response. When I use

ifort -c -fpp test.f90

I got:

test.f90(6): #error: #if: parse error.

mecej4 · ‎05-20-2022

Your program contains the directive #ELIF instead of #ELSE.

#IFDEF <symbol>

..

#ELIF <condition>

..

#ENDIF

versus

#IFDEF <symbol>

..

#ELSE

..

#ENDIF

wenbinyu · ‎05-20-2022

Yes, this fixes the issue. Thanks a lot! Now I have another question. If defined flag, I want to include file1.f90, if not defined include file2.f90. How can this be done? I tried the following. It does not work.
#IFDEF Flag
include 'file1.f90'

#else

include 'file2.f90'

#ENDIF

mecej4 · ‎05-20-2022

Did you remember to use the /fpp or -fpp option?

Simply saying "It does not work" is not helpful. You have to describe the command that you used, provide information regarding the contents of the source file, and display the error messages that you saw.

wenbinyu · ‎05-21-2022

Attached are three files. When I compile using

ifort -fpp test.f90 -o test

I execute test and obtain
15.00000
Not Compiled with Flag defined or compiled with Flag not defined

When I compile using

ifort -DFlag -fpp test.f90 -o test

I execute test and obtain
15.00000
Compiled with Flag defined

I was expecting the second number to be 200.00000

mecej4 · ‎05-21-2022

Preprocessors (originating in relation to C rather than Fortran) are usually case sensitive. Make sure that your preprocessor macros such as #ifdef are lowercase, and that macro arguments such as FLAG, etc., are uppercase (or at least consistently cased). You spelled "include" as "inlcude" in one place.

wenbinyu · ‎05-21-2022

Thanks a lot. After fixing a few typos, now it works.