CMake Fortran Issues: Difference between revisions

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= Introduction =
This page has moved [https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/languages/fortran/Fortran-Issues here].
CMake has a number of Fortran issues that have been discussed many different times on list and duplicated a fair number of times in the bug tracker as well.
 
Maik Beckmann is trying to make sense of all the confusion by collecting information on all Fortran issues at http://www.cmake.org/Bug/view.php?id=5809
 
Please join the work there by
 
* Contributing patches.
* Testing the patches that already exist there.
* Reporting things that don't work.
* Sending simplified examples of things which don't work.
* Sharing your expert knowledge of CMake.
 
= Concepts expressed using Makefiles =
 
This section is intended to discuss the makefile rules which CMake has to
generate.
 
== A simple program ==
 
A f9x program which is build by compiling in linking two source files ''a.f90'' and ''main.f90''.
The tree structure is:
* example_simpleProgram
** build
***  Makefile
*** prog.dir
**** build.make
** main.f90
** a.f90
 
a.f90:
<pre>
SUBROUTINE printHello
    WRITE(*,*) "Hello f9x world"
END SUBROUTINE
</pre>
 
main.f90:
<pre>
PROGRAM hello
    CALL printHello
END PROGRAM
</pre>
 
Makefile:
<pre>
all: prog.dir/all
 
prog.dir/all:
$(MAKE) -f prog.dir/build.make prog.dir/all
 
clean:
$(MAKE) -f prog.dir/build.make prog.dir/clean
</pre>
 
build.make:
<pre>
prog.dir/all: prog.dir/prog
 
prog.dir/prog:  prog.dir/a.o prog.dir/main.o
gfortran -o prog.dir/prog  prog.dir/a.o prog.dir/main.o
prog.dir/a.o: ../a.f90
gfortran -o prog.dir/a.o  -c ../a.f90
prog.dir/main.o: ../main.f90
gfortran -o prog.dir/main.o  -c ../main.f90
prog.dir/clean:
rm prog.dir/a.o prog.dir/main.o prog.dir/prog
</pre>
 
Now change into ''build'' and type
: $ make
to build. The current CMake is able to build the same without any problems. This is also valid for any fortran code that doesn't use modules.
 
You can download this example as tarball example_simpleProgram.tar.gz at http://www.cmake.org/Bug/view.php?id=5809
 
== A simple program with module ==
 
The same as before, but now ''a.f90'' provides a module which ''main.f90'' uses.
The tree structure is:
* example_simpleProgram_withModule
** build
***  Makefile
*** prog.dir
**** build.make
** main.f90
** a.f90
 
a.f90:
<pre>
MODULE localMod
!
CONTAINS
    SUBROUTINE printHello
        WRITE(*,*) "Hello f9x world"
    END SUBROUTINE
END MODULE
</pre>
 
main.f90:
<pre>
PROGRAM hello
    USE localMod
    CALL printHello
END PROGRAM
</pre>
 
Makefile:
<pre>
all: prog.dir/all
 
prog.dir/all:
$(MAKE) -f prog.dir/build.make prog.dir/all
 
clean:
$(MAKE) -f prog.dir/build.make prog.dir/clean
</pre>
 
build.make:
<pre>
prog.dir/all: prog.dir/prog
 
 
prog.dir/prog:  prog.dir/a.o prog.dir/main.o
gfortran -o prog.dir/prog  prog.dir/a.o prog.dir/main.o
 
prog.dir/a.o: ../a.f90
gfortran -o prog.dir/a.o  -c ../a.f90 -M prog.dir
prog.dir/localmod.mod: prog.dir/a.o
prog.dir/main.o: ../main.f90 prog.dir/localmod.mod
gfortran -o prog.dir/main.o -c ../main.f90 -I prog.dir
prog.dir/clean:
rm prog.dir/localmod.mod prog.dir/a.o prog.dir/main.o prog.dir/prog
</pre>
 
Now change into ''build'' and type
: $ make
to build.  This is nothing the current CMake can't do.  Now
do (you're at the build directory)
  $ touch ../a.f90
and enter
  $ make
again.  You'll see that a.f90 is recompiled, like the current CMake does,
but main.f90  is recompiled too!  This is different from current CMake, but its
the right way, since a module dependency is a compile time dependency like an
include.

Latest revision as of 15:41, 30 April 2018


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