Fortran Undefined Reference Error

Question

I've installed gfortran through the MinGW-get installer. I'm facing issues when I call a subroutine in Fortran and try to compile. I have written a small program Hello.F and a subroutine World.F such that program Hello.F calls Subroutine World.F

When I compile Hello.f using the command gfortran Hello.F I see an error as below,

Undefined Reference to 'World_'

collect2.exe: error: Id returned 1 exit status

Below is Hello.F,

PROGRAM HELLO
CALL WORLD
STOP
END

Below is World.F

SUBROUTINE WORLD
print *, "Hello World!"
RETURN
END

Both programs Hello.F and World.F reside in the same folder and I cd to this folder before typing in the command gfortran hello.f to compile the program.

I suggest you to find some good textbook or tutorial from this century for your beginnings. You are programming in a 40 years old style which should be forgotten. Learn particularly about Fortran 95, free form source and other more recent stuff (25 years old). Learn about line indentation and why you do not need all the `RETURN` and `STOP`. — Vladimir F Героям слава, Oct 18 '17 at 08:59

score 0 · Accepted Answer · answered Oct 17 '17 at 09:24

0

You may want to read up a bit here:

https://gcc.gnu.org/wiki/GFortranUsage

Specifically, you need to tell the compiler about all your files, for instance like this:

gfortran -o executable source1.f90 source2.f90

Or in your case:

gfortran -o helloworld Hello.F World.F

answered Oct 17 '17 at 09:24

NichtJens

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Thanx so much, this one worked. but in my actual scenario I have 100s of subroutine files. Is there a way to automate this? – Giri Oct 17 '17 at 09:46
Great! The standard way of automatizing this is a Makefile. See here: https://stackoverflow.com/questions/5871780/creating-a-fortran-makefile – NichtJens Oct 17 '17 at 10:47

Fortran Undefined Reference Error

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