[Flang] macro + comment + line continuation

[ye-luo]

main.f90

#define DEV_ACC !!!

program aa
implicit none

integer i,j,a
DEV_ACC data &
DEV_ACC & copyin(i)
do i=1,10
do j=1,10
  a=1
enddo
enddo
end program

got

$ flang-new -cpp main.f90 
error: Could not parse main.f90
./main.f90:13:4: error: expected end of statement
  enddo
     ^
./main.f90:13:1: in the context: END PROGRAM statement
  enddo
  ^
./main.f90:3:1: in the context: main program
  program aa
  ^

gfortran -cpp main.f90 works

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Ye Luo (ye-luo)

main.f90 ``` #define DEV_ACC !!!

program aa
implicit none

integer i,j,a
DEV_ACC data &
DEV_ACC & copyin(i)
do i=1,10
do j=1,10
a=1
enddo
enddo
end program

got

$ flang-new -cpp main.f90
error: Could not parse main.f90
./main.f90:13:4: error: expected end of statement
enddo
^
./main.f90:13:1: in the context: END PROGRAM statement
enddo
^
./main.f90:3:1: in the context: main program
program aa
^

`gfortran -cpp main.f90` works


</details>

[llvmbot]

@llvm/issue-subscribers-bug

Author: Ye Luo (ye-luo)

main.f90 ``` #define DEV_ACC !!!

program aa
implicit none

integer i,j,a
DEV_ACC data &
DEV_ACC & copyin(i)
do i=1,10
do j=1,10
a=1
enddo
enddo
end program

got

$ flang-new -cpp main.f90
error: Could not parse main.f90
./main.f90:13:4: error: expected end of statement
enddo
^
./main.f90:13:1: in the context: END PROGRAM statement
enddo
^
./main.f90:3:1: in the context: main program
program aa
^

`gfortran -cpp main.f90` works


</details>

[jeffhammond]

The code used in this test is just terrible and should be removed from whatever app is doing it.

It doesn't compile with Intel Fortran either.

$ ifx bad.F90
bad.F90(8): error #5082: Syntax error, found END-OF-STATEMENT when expecting one of: ( , % . /
 & copyin(i)
------------^
compilation aborted for bad.F90 (code 1)
$ ifort bad.F90
bad.F90(8): error #5082: Syntax error, found END-OF-STATEMENT when expecting one of: ( , % . /
 & copyin(i)
------------^
compilation aborted for bad.F90 (code 1)

[ye-luo]

@jeffhammond This is mock-up code. To use Intel compilers, one additional compiler option -allow nofpp_comments is needed.

$ ifx -fpp -allow nofpp_comments main.f90 # works.
$ ifx -fpp main.f90
main.f90(8): error #5082: Syntax error, found END-OF-STATEMENT when expecting one of: ( , % . /
 & copyin(i)
------------^
compilation aborted for main.f90 (code 1)

[ye-luo]

The preprocessor seems buggy.

flang-new -cpp repro.f90 -E
#line "./repro.f90" 3
      program aa
      implicit none

      integer i,j,a



      do j=1,10
      a=1
      enddo
      enddo
      end program

the loop i went missing.

[ye-luo]

@klausler I assigned you because I saw you working on the preprocessor. Do you mind taking a look?

[klausler]

f18 processes Fortran continuation lines before performing macro replacement, so

DEV_ACC data &
DEV_ACC & copyin(i)
do I=1,10

becomes

DEV_ACC data DEV_ACC do I=1,10

with a warning about extraneous tokens (copyin(i)) after the continuation marker

and then is ignored as a comment when DEV_ACC is replaced with !!!.

I suggest that you try using a macro for & if you want to play these games with preprocessing and also want code portability.

[jeffhammond]

This is not a bug. There is no standard Fortran preprocessor. This code only works with GCC cpp. If you want that, then put it in the build system explicitly the way that NWChem does (for a different reason than the one here). You cannot expect Flang to support cpp in the front-end.