Write my main program and module in different files

Help
1

When I write my main program and module in different files, it can’t work well.

I give an example.
Since I’m a newcomer, I can only put up one picture and I’ll give the details in words. I have two files, one is bin.f90, the other is bin_module.f90. These two files are in the same folder, in which bin is my main program, it uses bin_module.f90, but the compilation has not been able to pass!
bin.f90

program bin
use bin_module

implicit none
i = 1
write (*, *) i
end program bin

bin_module.f90

module bin_module
implicit none

! Trival variables
integer :: i

contains

end module bin_module

Here’s the result.

image
image1680×126 27.2 KB

It confuses me for many days.

2

Welcome to the forum.

The file bin_module.f90 need not contain a contains line when there are no subroutines or functions that are to be contained.

Your build system may have to be coaxed into ensure that it has compiled bin_module.f90 without errors before attempting to compile bin.f90. It may also need encouragement to get it to display build errors to the user.

3

Although the contains statement is unnecessary, as pointed out, using either PowerShell (which the OP is using, based on the error message) or Windows CMD, the command gfortran bin_module.f90 bin.f90 creates an executable.

4

I tried your suggestion, unfortunately the compilation still doesn’t pass.
bin_module.f90 just has few lines.I think no error in bin_module.f90.

image
image1721×1025 81.6 KB

5

Your build system is not issuing the correct gfortran command to compile and link the two source files. Note that the first command in your screenshot should have contained bin_module.f90 (or bin_module.o, if that file has already been compiled).

6

This is my folder.If I have a .mod file, does that mean bin_module_f90 has been compiled?

image
image2165×348 36.4 KB

If not, how I can compile it?

7

When bin_module.f90 is compiled, two files are generated – bin_module.mod and bin_module.o . Your IDE is showing the .mod file. Presumably, the same subdirectory also contains the object file bin_module.o, which should be linked with bin.o .

8

This post requires an understanding of the need for .mod files to be present for subsequent .f90 files that reference the .mod files via “use bin_module”. Order is important, which is not guaranteed by “gfortran -c *.f90”

I am also confused as to when bin_module.o is generated or required for linking. Certainly an empty contains section in the module definition does not help.

In the example above, only bin_module.mod is required to be present for bin.f90 to be compiled.

A set of interactive commands for cmd.exe that should work are:
gfortran -c bin_module.f90
grortran -c bin.f90
gfortran bin.o -o bin.exe
(or)
gfortran bin.o bin_module.o -o bin.exe
(or possibly)
gfortran *.o -o bin.exe

If this does not work, then there is a problem with the IDE being used ?

9

image
image1193×215 42 KB

I tried what you say, but it still not work. :smiling_face_with_tear:
I guess there is something wrong with my launch.json and task.json, because I found them myself from the web, after all, I’m not very familiar with this area.

10

I use JohnCampbell’s suggestion.

It has bin_module.o and bin.o.
image

11

The correct sequence of commands to perform is:

gfortran -c bin_module.f90
gfortran -c bin.f90
gfortran bin_module.o bin.o -o bin.exe

All .o files must be provided in the last command (link).