[Patch, fortran] PR23232 - DATA implied DO variables

["Paul Richard Thomas" <paul dot richard dot thomas at gmail dot com>]

:ADDPATCH fortran:

This patch came about as I was tidying up and putting to bed the
ongoing work on PRs, for others to follow up.  I had written this some
months ago but could not get it to handle error conditions without
segfaulting.  I noticed what this was due to this morning.....
blush.....

       gfc_error ("Beginning of message at %L followed by ",
                     "end of message", &expr->where);

I was completely blind to the errant comma and put the patch to one
side.... more blushing....  Since it is error_on_valid, I thought it
best to submit it myself, since I am up to speed on it.

Beyond this, the fix is straight forward.  Since the iterators are not
available, whilst gfc_match_init_expr and check_init_expr are doing
their respective things, the appearance of variable expressions for
the iterator start, end or steps causes errors.  The way around this
is to signal that we are matching a data statement and use this to
avoid checking for variable references.  In this way, all the other
good things happen, like checking for inquiry functions, etc.  The
expressions then go on to resolve.c, where in looping through the
iterators, they are copied and simplified.  Since the iterators are on
the iterator stack, simplification now works and EXPR_CONSTANTs are
produced.  The previous check that iterator expressions were constant
has now been removed.  The testcase is a rejigging of the reporter's;
the array is reduced in size so that the correct emplacement of the
values can be checked.

Regtested on PIV/Cygwin_NT - OK for trunk and, in a week, for 4.2?

Paul

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