Re: [PATCH] Fortran: improve attribute conflict checking [PR93635]

[Mikael Morin <morin-mikael@orange.fr>]

Le 09/05/2024 à 22:30, Harald Anlauf a écrit :
> Hi Mikael,
> 
> Am 09.05.24 um 21:51 schrieb Mikael Morin:
>> Hello,
>>
>> Le 06/05/2024 à 21:33, Harald Anlauf a écrit :
>>> Dear all,
>>>
>>> I've been contemplating whether to submit the attached patch.
>>> It addresses an ICE-on-invalid as reported in the PR, and also
>>> fixes an accepts-invalid (see testcase), plus maybe some more,
>>> related due to incomplete checking of symbol attribute conflicts.
>>>
>>> The fix does not fully address the general issue, which is
>>> analyzed by Steve: some of the checks do depend on the selected
>>> Fortran standard, and under circumstances such as in the testcase
>>> the checking of other, standard-version-independent conflicts
>>> simply does not occur.
>>>
>>> Steve's solution would fix that, but unfortunately leads to issues
>>> with error recovery in notoriously fragile parts of the FE: e.g.
>>> testcase pr87907.f90 needs adjusting, and minor variations
>>> of it will lead to various other horrendous ICEs that remind
>>> of existing PRs where parsing or resolution goes sideways.
>>>
>>> I therefore propose a much simpler approach: move - if possible -
>>> selected of the standard-version-dependent checks after the
>>> version-independent ones.  I think this could help in getting more
>>> consistent error reporting and recovery.  However, I did *not*
>>> move those checks that are critical when processing interfaces.
>>> (-> pr87907.f90 / (sub)modules)
>>>
>> Your patch looks clean, but I'm concerned that the order of the checks
>> should be the important ones first, regardless of their standard
>> version.  I'm trying to look at the ICE caused by your other tentative
>> patch at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93635#c6 but I
>> can't reproduce the problem.  Do you by any chance have around some of
>> the variations causing "horrendous" ICEs?
> 
> Oh, that's easy.  Just move the block
> 
>    conf_std (allocatable, dummy, GFC_STD_F2003);
>    conf_std (allocatable, function, GFC_STD_F2003);
>    conf_std (allocatable, result, GFC_STD_F2003);
> 
> towards the end of the gfc_check_conflict before the return true.
> 
> While the error messages for the original gfortran.dg/pr87907.f90
> look harmless, commenting out the main program p I get:
> 
> pr87907.f90:15:18:
> 
>     15 |       subroutine g(x)   ! { dg-error "mismatch in argument" }
>        |                  1
> Error: FUNCTION attribute conflicts with SUBROUTINE attribute in 'g' at (1)
> f951: internal compiler error: Segmentation fault
> 0x13b8ec2 crash_signal
>          ../../gcc-trunk/gcc/toplev.cc:319
> 0xba530e free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4026
> 0xba5319 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4026
> 0xba5319 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4026
> 0xba5319 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4026
> 0xba5609 gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4168
> 0xba39c1 gfc_free_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3173
> 0xba3b89 gfc_release_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3216
> 0xba5339 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4029
> 0xba5609 gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4168
> 0xba58ef gfc_symbol_done_2()
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4236
> 0xb12ec8 gfc_done_2()
>          ../../gcc-trunk/gcc/fortran/misc.cc:387
> 0xb4ac7f clean_up_modules
>          ../../gcc-trunk/gcc/fortran/parse.cc:7057
> 0xb4af02 translate_all_program_units
>          ../../gcc-trunk/gcc/fortran/parse.cc:7122
> 0xb4b735 gfc_parse_file()
>          ../../gcc-trunk/gcc/fortran/parse.cc:7413
> 0xbb626f gfc_be_parse_file
>          ../../gcc-trunk/gcc/fortran/f95-lang.cc:241
> 
> 
> Restoring the main program but simply adding "end subroutine g"
> where it is naively expected gives:
> 
> pr87907.f90:15:18:
> 
>     15 |       subroutine g(x)   ! { dg-error "mismatch in argument" }
>        |                  1
> Error: FUNCTION attribute conflicts with SUBROUTINE attribute in 'g' at (1)
> pr87907.f90:16:9:
> 
>     16 |       end subroutine g
>        |         1
> Error: Expecting END SUBMODULE statement at (1)
> pr87907.f90:20:7:
> 
>     20 |    use m                ! { dg-error "has a type" }
>        |       1
>     21 |    integer :: x = 3
>     22 |    call g(x)            ! { dg-error "which is not consistent
> with" }
>        |
>      2
> Error: 'g' at (1) has a type, which is not consistent with the CALL at (2)
> f951: internal compiler error: in gfc_free_namespace, at
> fortran/symbol.cc:4164
> 0xba55e1 gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4164
> 0xba39c1 gfc_free_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3173
> 0xba3b89 gfc_release_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3216
> 0xba5339 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4029
> 0xba5609 gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4168
> 0xba58ef gfc_symbol_done_2()
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4236
> 0xb12ec8 gfc_done_2()
>          ../../gcc-trunk/gcc/fortran/misc.cc:387
> 0xb4ac7f clean_up_modules
>          ../../gcc-trunk/gcc/fortran/parse.cc:7057
> 0xb4af02 translate_all_program_units
>          ../../gcc-trunk/gcc/fortran/parse.cc:7122
> 0xb4b735 gfc_parse_file()
>          ../../gcc-trunk/gcc/fortran/parse.cc:7413
> 0xbb626f gfc_be_parse_file
>          ../../gcc-trunk/gcc/fortran/f95-lang.cc:241
> 
> Now adding -std=f2018 to the compiler flags I get:
> 
> pr87907.f90:15:18:
> 
>     15 |       subroutine g(x)   ! { dg-error "mismatch in argument" }
>        |                  1
> Error: FUNCTION attribute conflicts with SUBROUTINE attribute in 'g' at (1)
> pr87907.f90:16:9:
> 
>     16 |       end subroutine g
>        |         1
> Error: Expecting END SUBMODULE statement at (1)
> pr87907.f90:20:7:
> 
>     20 |    use m                ! { dg-error "has a type" }
>        |       1
>     21 |    integer :: x = 3
>     22 |    call g(x)            ! { dg-error "which is not consistent
> with" }
>        |
>      2
> Error: 'g' at (1) has a type, which is not consistent with the CALL at (2)
> free(): invalid pointer
> f951: internal compiler error: Aborted
> 0x13b8ec2 crash_signal
>          ../../gcc-trunk/gcc/toplev.cc:319
> 0xba584f gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4207
> 0xba39c1 gfc_free_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3173
> 0xba3b89 gfc_release_symbol(gfc_symbol*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:3216
> 0xba5339 free_sym_tree
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4029
> 0xba5609 gfc_free_namespace(gfc_namespace*&)
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4168
> 0xba58ef gfc_symbol_done_2()
>          ../../gcc-trunk/gcc/fortran/symbol.cc:4236
> 0xb12ec8 gfc_done_2()
>          ../../gcc-trunk/gcc/fortran/misc.cc:387
> 0xb4ac7f clean_up_modules
>          ../../gcc-trunk/gcc/fortran/parse.cc:7057
> 0xb4af02 translate_all_program_units
>          ../../gcc-trunk/gcc/fortran/parse.cc:7122
> 0xb4b735 gfc_parse_file()
>          ../../gcc-trunk/gcc/fortran/parse.cc:7413
> 0xbb626f gfc_be_parse_file
>          ../../gcc-trunk/gcc/fortran/f95-lang.cc:241
> 
> I'll stop here...
> 
Thanks. Go figure, I have no problem reproducing today.
It's PR99798 (and there is even a patch for it).

> We currently do not recover well from errors, and the prevention
> of corrupted namespaces is apparently a goal we aim at.
> 
Yes, and we are not there yet. But at least there is a sensible error 
message before the crash.

> Cheers,
> Harald
> 
>>> The patch therefore does not require any testsuite update and
>>> should not give any other surprises, so it should be very safe.
>>> The plan is also to leave the PR open for the time being.
>>>
>>> Regtesting on x86_64-pc-linux-gnu.  OK for mainline?
>>>
>>> Thanks,
>>> Harald
>>>
>>
>>
>