Re: [PATCH] PR fortran/99205 - [10/11 Regression] Out of memory with undefined character length

[Tobias Burnus <tobias@codesourcery.com>]

Dear Harald, dear all,

On 09.03.21 20:45, Harald Anlauf via Fortran wrote:
> character variables with undefined length are not allowed as
> objects in DATA statements.  We better reject them.
>
> Regtested on x86_64-pc-linux-gnu.  OK for master / backport?
>
> PR fortran/99205 - Out of memory with undefined character length
>
> A variable that is a data statement object shall be a designator,
> thus a character variable shall have a constant length.

This comment is wrong: A designator does not imply this – nor is
F2018:C875 violated, not even the substring starting/ending point
const expr bit.


The reason that it is not permitted is the "automatic data object"
(see *...* highlighted parts in the quote):

C876   (R839) A *variable* whose *designator* appears as a
*data-stmt-object* or a data-i-do-object hall not be a
dummy argument, accessed by use or host association,
in a named common block unless the DATA statement is
in a block data program unit, in blank common, a function name,
a function result name, an *automatic* *data* *object,*
or an allocatable variable.

With the definition: "3.11 automatic data object
nondummy data object with a type parameter or array bound that
depends on the value of aspecification-expr that is not
a constant expression (8.3)"


In the following variant of the program, the invalid
variable declaration of 'c' itself is avoided by using
a block:

integer :: ll
ll = 4
block
   character(ll) :: c(2), cc(2)
   character(ll) :: c2(2), cc2(2)
   data c /'a', 'b'/
   data c2(:)(1:1) /'a', 'b'/
   common /block/ cc, cc2
end block
end

You may consider to update your testcase or to
augment your testcase.

The patch itself is OK, but you really need to
update the commit description.

Tobias

>
> gcc/fortran/ChangeLog:
>
>       PR fortran/99205
>       * data.c (gfc_assign_data_value): Reject non-constant character
>       length for lvalue.
>
> gcc/testsuite/ChangeLog:
>
>       PR fortran/99205
>       * gfortran.dg/pr99205.f90: New test.
>
>
> pr99205.patch
>
> diff --git a/gcc/fortran/data.c b/gcc/fortran/data.c
> index 25e97930169..71e2552025d 100644
> --- a/gcc/fortran/data.c
> +++ b/gcc/fortran/data.c
> @@ -595,6 +595,9 @@ gfc_assign_data_value (gfc_expr *lvalue, gfc_expr *rvalue, mpz_t index,
>         /* An initializer has to be constant.  */
>         if (lvalue->ts.u.cl->length == NULL && !(ref && ref->u.ss.length != NULL))
>       return false;
> +      if (lvalue->ts.u.cl->length
> +       && lvalue->ts.u.cl->length->expr_type != EXPR_CONSTANT)
> +     return false;
>         expr = create_character_initializer (init, last_ts, ref, rvalue);
>         if (!expr)
>       return false;
> diff --git a/gcc/testsuite/gfortran.dg/pr99205.f90 b/gcc/testsuite/gfortran.dg/pr99205.f90
> new file mode 100644
> index 00000000000..ed0782ce8a0
> --- /dev/null
> +++ b/gcc/testsuite/gfortran.dg/pr99205.f90
> @@ -0,0 +1,11 @@
> +! { dg-do compile }
> +! PR fortran/99205 - Out of memory with undefined character length
> +! { dg-options "-w" }
> +
> +program p
> +  character(l) :: c(2) ! { dg-error "must have constant character length" }
> +  data c /'a', 'b'/
> +  common c
> +end
> +
> +! { dg-error "cannot appear in the expression at" " " { target *-*-* } 6 }
-----------------
Mentor Graphics (Deutschland) GmbH, Arnulfstrasse 201, 80634 München Registergericht München HRB 106955, Geschäftsführer: Thomas Heurung, Frank Thürauf