bug: compiling a source file which calls a subroutine contained entirely in a single file fails

[kmr-srbh]

Minimum Reproducible Example

test_subroutine.f90

SUBROUTINE test_subroutine
   PRINT *, "Call Result: SUCCESS"
END SUBROUTINE test_subroutine

test_program.f90

PROGRAM test_program
   CALL test_subroutine
END PROGRAM test_program

Output

GFortran

We compile and execute this with GFortran using the below commands:

gfortran -c ./examples/test_subroutine.f90 -o ./examples/test_subroutine.o  # compile subroutine to binary
gfortran -c ./examples/test_program.f90 -o ./examples/test_program.o  # compile program to binary
gfortran -o ./examples/my_program ./examples/test_program.o ./examples/test_subroutine.o  # link binaries
./examples/my_program  # execute the program

The output is as expected:

(base) saurabh-kumar@Awadh:~/Projects/System/lfortran$ ./examples/my_program
 Call Result: SUCCESS

LFortran

LFortran compiles the subroutine file successfully, but fails to compile the program file.

(base) saurabh-kumar@Awadh:~/Projects/System/lfortran$ lfortran -c ./examples/test_subroutine.f90 -o ./examples/test_subroutine.o  # compile subroutine to binary
(base) saurabh-kumar@Awadh:~/Projects/System/lfortran$ lfortran -c ./examples/test_program.f90 -o ./examples/test_program.o  # compile program to binary
semantic error: Function 'test_subroutine' not found or not implemented yet (if it is intrinsic)
 --> ./examples/test_program.f90:2:4
  |
2 |    CALL test_subroutine
  |    ^^^^^^^^^^^^^^^^^^^^ 


Note: Please report unclear, confusing or incorrect messages as bugs at
https://github.com/lfortran/lfortran/issues.

This bug was caught when trying to compile the file snap_main.f90 which has a call to a subroutine translv contained in a file of it's own - translv.f90. I feel this is an important issue because separating subroutines into their own files is commonly observed in legacy code-bases.

[assem2002]

Try these commands

lfortran test_subroutine.f90  --generate-object-code -c
lfortran test_program.f90  --implicit-interface -c
lfortran test_program.o test_subroutine.o

Call Result: SUCCESS

I had similar issue here #4008

[assem2002]

I think we need just to add these flags --generate-object-code , --implicit-interface to makefile

[kmr-srbh]

Try these commands. I had similar issue here #4008

Ah! Right! I am not sure if GFortran is doing the same internally, but the approach provided by you can surely work for us. Thanks! 👍

[certik]

The --generate-object-code does not work for modules though as well as for many modern features, since they are often implemented using a global ASR->ASR pass which changes the signature.

You can try to compile the global subroutines using --generate-object-code, but it might not work. In that case I recommend adding them to a module, compile as usual, and import it from the module where they are used. Once we fully compile SNAP, we'll get back to this issue.