Re: [patch, fortran] Fix PR 91443

[Janne Blomqvist <blomqvist dot janne at gmail dot com>]

On Thu, Aug 15, 2019 at 2:35 PM Thomas Koenig <tkoenig@netcologne.de> wrote:
>
> Hello world,
>
> this patch fixes PR 91443, in which we did not warn about a mismatched
> external procedure. The problem was that the module this was called in
> was resolved before parsing of the procedure ever started.
>
> The approach taken here is to move the checking of external procedures
> to a stage after normal resolution.  And, of course, fix the resulting
> fallout from regression-testing :-)
> There is also one policy change in the patch. Previously, we only warned
> about mismatched declarations.  Now, this is a hard error unless the
> user specifies -std=legacy.  The reason is that we have not yet solved
> our single declaration problem, but it cannot be solved unless all
> of a procedure's callers match.  People who have such broken code
> should at least be made aware that they have a problem. However, I would
> like to have some sort of agreement on this point before the patch
> is committed.  This can also be changed (see the code at the bottom
> of frontend-passes.c).

Personally, I'm fine with making this a hard error. As we've recently
seen with the varargs & missing charlengths in LAPACK saga, mismatches
can cause extremely subtle issues that can cause silent corruption and
take an expert to figure out.

> Once this is in, the next step is to issue errors for mismatching
> calls where the callee is not in the same file.  This can be done
> with the infrastructure of this patch.
>
> So, OK for trunk?

The patch itself looks Ok. One worry, are you introducing an
O(N**2)(?) algorithm (looping over all symbols for every symbol?), and
does this cause performance issues when compiling some gigantic F77
project?

If this worry is unfounded, Ok for trunk.

-- 
Janne Blomqvist