| Message ID | CAKwh3qjqYF3ozbX36hEpvjCVB0HrjbcbpadX7j_Zz8xb9GHDfg@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
ping! 2016-11-19 10:12 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: > Hi all, > >> I previously assumed that the test case for this PR would be legal, >> but by now I think that's wrong. The test case should be rejected, and >> we already have checking mechanisms for this (see >> resolve_fl_variable), but apparently they are not working. >> >> My current suspicion is that 'gfc_is_constant_expr' has a bug, because >> it claims the call to the function 'get_i' to be a constant >> expression. This is not true, because get_i() can not be reduced to a >> compile-time constant. > > some more reading in the standard confirms this suspicion: In > gfc_is_constant_expr there is a piece of code which claims that > specification functions are constant. That is certainly not true, and > so what I'm doing in the attached fix is to remove that code and add > some references to the standard to make things clearer. > > The code that I'm removing has last been touched in this commit by > Jerry six years ago: > > https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520 > > However, this did not introduce the bug in the first place (not sure > when that happened). > > In any case the new patch in the attachment regtests cleanly and > correctly rejects the original test case as well as one of the cases > mentioned by Dominique. Ok for trunk? > > Cheers, > Janus > > > > 2016-11-19 Janus Weil <janus@gcc.gnu.org> > > PR fortran/78392 > * expr.c (gfc_is_constant_expr): Specification functions are not > compile-time constants. Update documentation (add reference to F08 > standard), add a FIXME. > (external_spec_function): Add reference to F08 standard. > * resolve.c (resolve_fl_variable): Ditto. > > 2016-11-19 Janus Weil <janus@gcc.gnu.org> > > PR fortran/78392 > * gfortran.dg/constant_shape.f90: New test case.
> Le 26 nov. 2016 à 10:45, Janus Weil <janus@gcc.gnu.org> a écrit : > > ping! > The patch is working has expected. Note the removed block has been introduced by Daniel Franke at r126826. Dominique.
2016-11-26 17:37 GMT+01:00 Dominique d'Humières <dominiq@lps.ens.fr>: > >> Le 26 nov. 2016 à 10:45, Janus Weil <janus@gcc.gnu.org> a écrit : >> >> ping! >> > The patch is working has expected. Note the removed block has been introduced by Daniel Franke at r126826. Right, thanks for the reference. I think that commit is plain wrong, at least the part that says "Specification functions are constant". One can easily construct a specification function that is not a compile-time constant. For example, just take the module function "get_i" in the test case and have it depend on a variable declared in the module header. module mytypes implicit none integer, save :: i = 13 contains pure integer function get_i () get_i = i end function subroutine set_i (j) integer, intent(in) :: j i = j end subroutine end module Cheers, Janus
double-ping! 2016-11-26 10:45 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: > ping! > > > 2016-11-19 10:12 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >> Hi all, >> >>> I previously assumed that the test case for this PR would be legal, >>> but by now I think that's wrong. The test case should be rejected, and >>> we already have checking mechanisms for this (see >>> resolve_fl_variable), but apparently they are not working. >>> >>> My current suspicion is that 'gfc_is_constant_expr' has a bug, because >>> it claims the call to the function 'get_i' to be a constant >>> expression. This is not true, because get_i() can not be reduced to a >>> compile-time constant. >> >> some more reading in the standard confirms this suspicion: In >> gfc_is_constant_expr there is a piece of code which claims that >> specification functions are constant. That is certainly not true, and >> so what I'm doing in the attached fix is to remove that code and add >> some references to the standard to make things clearer. >> >> The code that I'm removing has last been touched in this commit by >> Jerry six years ago: >> >> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520 >> >> However, this did not introduce the bug in the first place (not sure >> when that happened). >> >> In any case the new patch in the attachment regtests cleanly and >> correctly rejects the original test case as well as one of the cases >> mentioned by Dominique. Ok for trunk? >> >> Cheers, >> Janus >> >> >> >> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >> >> PR fortran/78392 >> * expr.c (gfc_is_constant_expr): Specification functions are not >> compile-time constants. Update documentation (add reference to F08 >> standard), add a FIXME. >> (external_spec_function): Add reference to F08 standard. >> * resolve.c (resolve_fl_variable): Ditto. >> >> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >> >> PR fortran/78392 >> * gfortran.dg/constant_shape.f90: New test case.
Hi all, I hate to ping this patch once more, but somehow we need to come to a conclusion here. The issue boils down to the fact that there is a piece of code in the gfortran code which claims that specification functions are 'constant', but I doubt that this is true. To my understanding the concept of specification expressions and specification functions (see section 7.1.6 in the F03 standard) was introduced essentially to refer to side-effect-free expressions that can be used e.g. in a type-specification context (array bounds, char-length parameters etc). However I think 'specification functions' do not necessarily need to be 'constants', in the sense that subsequent invocations give always the same (constant) result and their value can be determined at compile time. My patch is at: https://gcc.gnu.org/ml/fortran/2016-11/msg00188.html Further discussion at: https://gcc.gnu.org/ml/fortran/2016-11/msg00243.html Any comments, please!?! Cheers, Janus 2016-12-03 8:05 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: > double-ping! > > > 2016-11-26 10:45 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >> ping! >> >> >> 2016-11-19 10:12 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>> Hi all, >>> >>>> I previously assumed that the test case for this PR would be legal, >>>> but by now I think that's wrong. The test case should be rejected, and >>>> we already have checking mechanisms for this (see >>>> resolve_fl_variable), but apparently they are not working. >>>> >>>> My current suspicion is that 'gfc_is_constant_expr' has a bug, because >>>> it claims the call to the function 'get_i' to be a constant >>>> expression. This is not true, because get_i() can not be reduced to a >>>> compile-time constant. >>> >>> some more reading in the standard confirms this suspicion: In >>> gfc_is_constant_expr there is a piece of code which claims that >>> specification functions are constant. That is certainly not true, and >>> so what I'm doing in the attached fix is to remove that code and add >>> some references to the standard to make things clearer. >>> >>> The code that I'm removing has last been touched in this commit by >>> Jerry six years ago: >>> >>> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520 >>> >>> However, this did not introduce the bug in the first place (not sure >>> when that happened). >>> >>> In any case the new patch in the attachment regtests cleanly and >>> correctly rejects the original test case as well as one of the cases >>> mentioned by Dominique. Ok for trunk? >>> >>> Cheers, >>> Janus >>> >>> >>> >>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>> >>> PR fortran/78392 >>> * expr.c (gfc_is_constant_expr): Specification functions are not >>> compile-time constants. Update documentation (add reference to F08 >>> standard), add a FIXME. >>> (external_spec_function): Add reference to F08 standard. >>> * resolve.c (resolve_fl_variable): Ditto. >>> >>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>> >>> PR fortran/78392 >>> * gfortran.dg/constant_shape.f90: New test case.
Hi Janus, The patch is good - OK for trunk. Thanks Paul On 12 December 2016 at 16:52, Janus Weil <janus@gcc.gnu.org> wrote: > Hi all, > > I hate to ping this patch once more, but somehow we need to come to a > conclusion here. > > The issue boils down to the fact that there is a piece of code in the > gfortran code which claims that specification functions are > 'constant', but I doubt that this is true. To my understanding the > concept of specification expressions and specification functions (see > section 7.1.6 in the F03 standard) was introduced essentially to refer > to side-effect-free expressions that can be used e.g. in a > type-specification context (array bounds, char-length parameters etc). > > However I think 'specification functions' do not necessarily need to > be 'constants', in the sense that subsequent invocations give always > the same (constant) result and their value can be determined at > compile time. > > My patch is at: https://gcc.gnu.org/ml/fortran/2016-11/msg00188.html > Further discussion at: https://gcc.gnu.org/ml/fortran/2016-11/msg00243.html > > Any comments, please!?! > > Cheers, > Janus > > > > 2016-12-03 8:05 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >> double-ping! >> >> >> 2016-11-26 10:45 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>> ping! >>> >>> >>> 2016-11-19 10:12 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>>> Hi all, >>>> >>>>> I previously assumed that the test case for this PR would be legal, >>>>> but by now I think that's wrong. The test case should be rejected, and >>>>> we already have checking mechanisms for this (see >>>>> resolve_fl_variable), but apparently they are not working. >>>>> >>>>> My current suspicion is that 'gfc_is_constant_expr' has a bug, because >>>>> it claims the call to the function 'get_i' to be a constant >>>>> expression. This is not true, because get_i() can not be reduced to a >>>>> compile-time constant. >>>> >>>> some more reading in the standard confirms this suspicion: In >>>> gfc_is_constant_expr there is a piece of code which claims that >>>> specification functions are constant. That is certainly not true, and >>>> so what I'm doing in the attached fix is to remove that code and add >>>> some references to the standard to make things clearer. >>>> >>>> The code that I'm removing has last been touched in this commit by >>>> Jerry six years ago: >>>> >>>> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520 >>>> >>>> However, this did not introduce the bug in the first place (not sure >>>> when that happened). >>>> >>>> In any case the new patch in the attachment regtests cleanly and >>>> correctly rejects the original test case as well as one of the cases >>>> mentioned by Dominique. Ok for trunk? >>>> >>>> Cheers, >>>> Janus >>>> >>>> >>>> >>>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>>> >>>> PR fortran/78392 >>>> * expr.c (gfc_is_constant_expr): Specification functions are not >>>> compile-time constants. Update documentation (add reference to F08 >>>> standard), add a FIXME. >>>> (external_spec_function): Add reference to F08 standard. >>>> * resolve.c (resolve_fl_variable): Ditto. >>>> >>>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>>> >>>> PR fortran/78392 >>>> * gfortran.dg/constant_shape.f90: New test case.
2016-12-12 18:37 GMT+01:00 Paul Richard Thomas <paul.richard.thomas@gmail.com>: > Hi Janus, > > The patch is good - OK for trunk. Thanks, Paul. Committed as r243580. Cheers, Janus > On 12 December 2016 at 16:52, Janus Weil <janus@gcc.gnu.org> wrote: >> Hi all, >> >> I hate to ping this patch once more, but somehow we need to come to a >> conclusion here. >> >> The issue boils down to the fact that there is a piece of code in the >> gfortran code which claims that specification functions are >> 'constant', but I doubt that this is true. To my understanding the >> concept of specification expressions and specification functions (see >> section 7.1.6 in the F03 standard) was introduced essentially to refer >> to side-effect-free expressions that can be used e.g. in a >> type-specification context (array bounds, char-length parameters etc). >> >> However I think 'specification functions' do not necessarily need to >> be 'constants', in the sense that subsequent invocations give always >> the same (constant) result and their value can be determined at >> compile time. >> >> My patch is at: https://gcc.gnu.org/ml/fortran/2016-11/msg00188.html >> Further discussion at: https://gcc.gnu.org/ml/fortran/2016-11/msg00243.html >> >> Any comments, please!?! >> >> Cheers, >> Janus >> >> >> >> 2016-12-03 8:05 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>> double-ping! >>> >>> >>> 2016-11-26 10:45 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>>> ping! >>>> >>>> >>>> 2016-11-19 10:12 GMT+01:00 Janus Weil <janus@gcc.gnu.org>: >>>>> Hi all, >>>>> >>>>>> I previously assumed that the test case for this PR would be legal, >>>>>> but by now I think that's wrong. The test case should be rejected, and >>>>>> we already have checking mechanisms for this (see >>>>>> resolve_fl_variable), but apparently they are not working. >>>>>> >>>>>> My current suspicion is that 'gfc_is_constant_expr' has a bug, because >>>>>> it claims the call to the function 'get_i' to be a constant >>>>>> expression. This is not true, because get_i() can not be reduced to a >>>>>> compile-time constant. >>>>> >>>>> some more reading in the standard confirms this suspicion: In >>>>> gfc_is_constant_expr there is a piece of code which claims that >>>>> specification functions are constant. That is certainly not true, and >>>>> so what I'm doing in the attached fix is to remove that code and add >>>>> some references to the standard to make things clearer. >>>>> >>>>> The code that I'm removing has last been touched in this commit by >>>>> Jerry six years ago: >>>>> >>>>> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=166520 >>>>> >>>>> However, this did not introduce the bug in the first place (not sure >>>>> when that happened). >>>>> >>>>> In any case the new patch in the attachment regtests cleanly and >>>>> correctly rejects the original test case as well as one of the cases >>>>> mentioned by Dominique. Ok for trunk? >>>>> >>>>> Cheers, >>>>> Janus >>>>> >>>>> >>>>> >>>>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>>>> >>>>> PR fortran/78392 >>>>> * expr.c (gfc_is_constant_expr): Specification functions are not >>>>> compile-time constants. Update documentation (add reference to F08 >>>>> standard), add a FIXME. >>>>> (external_spec_function): Add reference to F08 standard. >>>>> * resolve.c (resolve_fl_variable): Ditto. >>>>> >>>>> 2016-11-19 Janus Weil <janus@gcc.gnu.org> >>>>> >>>>> PR fortran/78392 >>>>> * gfortran.dg/constant_shape.f90: New test case. > > > > -- > If you're walking down the right path and you're willing to keep > walking, eventually you'll make progress. > > Barack Obama
Index: gcc/fortran/expr.c =================================================================== --- gcc/fortran/expr.c (Revision 242620) +++ gcc/fortran/expr.c (Arbeitskopie) @@ -883,8 +883,9 @@ done: } -/* Function to determine if an expression is constant or not. This - function expects that the expression has already been simplified. */ +/* Determine if an expression is constant in the sense of F08:7.1.12. + * This function expects that the expression has already been simplified. + * FIXME: Return a bool, not an int. */ int gfc_is_constant_expr (gfc_expr *e) @@ -891,7 +892,6 @@ gfc_is_constant_expr (gfc_expr *e) { gfc_constructor *c; gfc_actual_arglist *arg; - gfc_symbol *sym; if (e == NULL) return 1; @@ -920,25 +920,6 @@ gfc_is_constant_expr (gfc_expr *e) return 0; } - /* Specification functions are constant. */ - /* F95, 7.1.6.2; F2003, 7.1.7 */ - sym = NULL; - if (e->symtree) - sym = e->symtree->n.sym; - if (e->value.function.esym) - sym = e->value.function.esym; - - if (sym - && sym->attr.function - && sym->attr.pure - && !sym->attr.intrinsic - && !sym->attr.recursive - && sym->attr.proc != PROC_INTERNAL - && sym->attr.proc != PROC_ST_FUNCTION - && sym->attr.proc != PROC_UNKNOWN - && gfc_sym_get_dummy_args (sym) == NULL) - return 1; - if (e->value.function.isym && (e->value.function.isym->elemental || e->value.function.isym->pure @@ -2741,7 +2722,8 @@ restricted_args (gfc_actual_arglist *a) /************* Restricted/specification expressions *************/ -/* Make sure a non-intrinsic function is a specification function. */ +/* Make sure a non-intrinsic function is a specification function, + * see F08:7.1.11.5. */ static bool external_spec_function (gfc_expr *e) Index: gcc/fortran/resolve.c =================================================================== --- gcc/fortran/resolve.c (Revision 242620) +++ gcc/fortran/resolve.c (Arbeitskopie) @@ -11831,8 +11831,8 @@ resolve_fl_variable (gfc_symbol *sym, int mp_flag) && !sym->attr.pointer && is_non_constant_shape_array (sym)) { - /* The shape of a main program or module array needs to be - constant. */ + /* F08:C541. The shape of an array defined in a main program or module + * needs to be constant. */ gfc_error ("The module or main program array %qs at %L must " "have constant shape", sym->name, &sym->declared_at); specification_expr = saved_specification_expr;