Re: [Patch, Fortran] PR fortran/83522 – reject array-valued substrings

[Tobias Burnus]

In light of the somehow missed test-suite fails and the discussion about 
rejecting too much, I have reverted the patch with commit r83522.

Tobias

Am 11.10.18 um 12:46 schrieb Jakub Jelinek:
> On Mon, Oct 08, 2018 at 09:44:57PM +0200, Tobias Burnus wrote:
>> as the PR (and the attached testcase) shows, gfortran doesn't handle
>> noncontiguous access with substrings. Namely, "str_array(:)(1:5)" is
>> mishandled (segfault while building the "tree" as expr == NULL).
>>
>> As Jerry has dug up in the standard (F2008, R610 alias F2018, R908),
>> substrings are only permitted on scalars (or array elements). – [gfortran
>> has some partial support for noncontiguous memory as actual argument the now
>> rejected test cases show.]
>>
>> In words of the standard (here: F2018):
>>
>> 9.4.1Â  Substrings
>>
>> A substring is a contiguous portion of a character string (7.4.4).
>>
>> R908   substring   is   parent-string  ( substring-range )
>>
>> R909Â Â  parent-string
>>              is   scalar-variable-name
>>              or  array-element
>>              or  coindexed-named-object
>>              or  scalar-structure-component
>>              or  scalar-constant
>>
>> The patch adds a check to the variable resolving – it comes too late to
>> print a nice error message for "string(:)(:)"; that statement gets matched
>> unsuccessfully and at the end the buffered error message of match_variable
>> (unexpected character "(") gets printed. – One could reject it earlier but
>> the code doesn't seem to be that nice. (See PR for a variant.)
>>
>> Build and regtested on x86_64-linux.
>> OK for the trunk?
> As I wrote in the PR, I believe it is incorrect and should be reverted.
> While for
>    character(kind=1,length=4) :: f(4,5)
> e.g.
>    f(:,:)(1:2)
> is not matching the substring non-terminal, it is IMNSHO matching the
> array-section non-terminal:
> R918   array-section
>  Â Â Â  Â Â Â  Â Â Â  is data-ref [ ( substring-range ) ]
>  Â Â Â  Â Â Â  Â Â Â  or complex-part-designator
> C925   (R918) Exactly one part-ref shall have nonzero rank, and either the final
> 	      part-ref shall have a section-subscript-list with nonzero rank, another
> 	      part-ref shall have nonzero rank, or the complex-part-designator
> 	      shall be an array.
> C926   (R918) If a substring-range appears, the rightmost part-name shall be of type
> 	      character.
> and in that case:
>
> An array element is a scalar. An array section is an array. If a substring-range
> appears in an array-section, each element is the designated substring of the
> corresponding element of the array section.
>
> applies.
>
> 	Jakub