[patch, fortran] Compile-time check for change in DO variable in contained procedures

Paul Richard Thomas paul.richard.thomas@gmail.com
Wed Aug 5 15:17:33 GMT 2020

Hi Thomas,

This is OK by me.

Is it worth testing the INTENT variants?



On Tue, 4 Aug 2020 at 20:03, Thomas Koenig via Fortran <fortran@gcc.gnu.org>

> Hello world,
> the attached patch issues an error for something that I am sure most
> people did at least once (I know I did), something like
>    do i=1,10
>       call foo
>    end do
> ...
> contains
>    subroutine foo
>      do i=1,5
>     ...
>      end do
> which is, of course, illegal, but the programmer's fault. We issue an
> error with -fcheck=all, but a compile-time is better, of course.
> As you can see from the modification of do_check_4.f90, you have to go
> to some lengths to fool the compiler with this patch.
> As an aside, I could really have used three places for the error
> message here.  As is, I settled for the place of the call from
> the DO loop checked, and the place where it is modified.  With
> the name of the variable, the user should be able to figure out
> what's wrong.
> Regression-tested. OK for trunk?
> Best regards
>         Thomas
> Static analysis for definition of DO index variables in contained
> procedures.
> When encountering a procedure call in a DO loop, this patch checks if
> the call is to a contained procedure, and if it is, check for
> changes in the index variable.
> gcc/fortran/ChangeLog:
>         PR fortran/96469
>         * frontend-passes.c (doloop_contained_function_call): New
>         function.
>         (doloop_contained_procedure_code): New function.
>         (CHECK_INQ): Macro for inquire checks.
>         (doloop_code): Invoke doloop_contained_procedure_code and
>         doloop_contained_function_call if appropriate.
>         (do_intent): Likewise.
> gcc/testsuite/ChangeLog:
>         PR fortran/96469
>         * gfortran.dg/do_check_4.f90: Hide change in index variable
>         from compile-time analysis.
>         * gfortran.dg/do_check_4.f90: New test.

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