[Bug fortran/114922] fsyntax-only need the modules

["mikael at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114922

Mikael Morin <mikael at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |mikael at gcc dot gnu.org

--- Comment #4 from Mikael Morin <mikael at gcc dot gnu.org> ---
(In reply to Axel Ehrich from comment #3)

> In my understanding, the intention of the option -fsyntax-only is to
> construct the module files needed to compile the code. A  build process
> would involve two steps: Step 1: construct all module files with gfortran
> -fsyntax only. Step 2: construct the object files without this option, while
> relying on the presence of all module files. (I have found this recipe on
> the internet and consider it valuable.)
> 
The normal process is to compile directly the files (without -fsyntax-only) in
the right order, in a single step.  Some people prefer to do it in two steps,
depending on their needs.

> Alternatively, the purpose of -fsyntax-only could be to save compile time by
> a doing quick first check before entering the time consuming parts of the
> compilation. 
Yes, that's the main purpose.

> If this syntax check goes so far that it requires the module
> files already, the goal mentioned above cannot be reached.

Yes, it can.  The files have to be compiled in the right order.

Keep in mind that the compiler processes one file at a time and doesn't have
a global knowledge of all the files together.

Consider this example:
  module m2
    use m1
  end module m2

What symbols should be made available in the module file for m2?
Don't you think that the knowledge of the content of m1 is needed?