API with and without null-terminated strings

[MakisH]

Closes #1, implementing (to the extent I understand) the suggestions of @ivan-pi.

I also tried to make the length an optional argument, to maintain compatibility with user code. I am also trying to avoid touching the preCICE C/Fortran bindings for now, as we just had a breaking release.

Currently, building the (unmodified) solverdummy.f90 leads to the following error:

fortran-module/examples/solverdummy [nullterminated]$ make
gfortran -g solverdummy.f90 -o solverdummy -I../.. -L/home/gc/repos/precice/precice/build -lprecice
/usr/bin/ld: /tmp/ccQ2PSRq.o: in function `MAIN__':
/home/gc/repos/precice/fortran-module/examples/solverdummy/solverdummy.f90:38: undefined reference to `__precice_MOD_precicef_create'

Any clue what I am doing wrong?

[MakisH]

I still want that users call precicef_create, so they should be outside the contains block. However, it looks like I cannot call subroutines from inside an interface. What would be the right way here?

[ivan-pi]

But you have it now as a module procedure (a thin wrapper of the preCICE C API). Isn't that what you want?

[MakisH]

I want that users call the precicef_create variant without having to provide neither null-terminated strings, nor placeholder lengths. For this, I would need the precicef_create to not be internal (inside the contains), no?

If I ask the users to call the precicec_create, then they need to provide null-terminated strings.

Should I maybe split it into two different modules? Not sure if I can modify the arguments in an interface.

[ivan-pi]

In Fortran parlance, interface blocks are like function declarations in C. They are specification statements (i.e. non-executable).

When you want to define a procedure, it must be in the "contains" part:

module precice
 ! ... specification ...
contains
 ! ... procedure definitions (including executable statements) ...
end module

[MakisH]

Ah, that helps! But then, I understand that both what I have in the interface and in the contains need to have the same name.