Untabified and resubmitted: Patch to gfortran PR13742

[Tobias Schlüter]

Victor Leikehman wrote:
>>
>>Is there a way to get this error to the front end?
> 
> 
> In theory, it may and should be reported in the front end.
> In practice, it is inconvenient. There are several errors
> in this area that are reported just like that --
> grep trans-common.c for gfc_error to see more examples. So
> this particular error message does not  make the situation
> any worse than it used to be.
> 

In that case it wasn't inconvenient. After looking up the language 
rules, enforcing the rules for initialization of COMMON variables meant 
putting two if's in the right places and emitting errors, unless I've 
missed something, of course.

[tobi@marktplatz fortran]$ grep -n gfc_error trans-common.c
460:        gfc_error ("bad array reference at %L", &s->where);
468:        gfc_error ("illegal reference type at %L as EQUIVALENCE object",
512:    gfc_error ("inconsistent equivalence rules involving '%s' at %L 
and "
625:        gfc_error ("the equivalence set for '%s' cause an invalid 
extension "

These are now PR15313 and I'm the assignee. The first two should be 
internal errors, I think the latter two can be caught in the frontend.

- Tobi