Re: [Patch, Fortran] PR 40881: warn for obsolescent features

["Manfred Schwarb" <manfred99 at gmx dot ch>]

> Hi all,
> 
> the Fortran 90 standard lists nine "obsolescent" f77 features, which
> continue to be supported in f90, but may be deleted in the future.
> Therefore their usage is discouraged by the standard. Currently, we
> only warn about two of them (arithmetic if and assumed length
> character functions). This patch adds warnings for four more:
> 
> * alternate return
> * computed goto
> * statement functions
> * old-style character lengths ["character*..." instead of
> "character(...)"]
> 
> That leaves three obsolescent features, which are not warned about:
> 
> * shared DO termination
> * DATA statements among executable statements
> * fixed form source
> 
> These may be added later.
> 
> The patch is technically very simple, but has a rather large impact on
> the testsuite, since lots of test cases use old-style character
> lengths. For most of them I just added -std=legacy. But some already
> use -std=f95, so I had to change the character lengths to f90 style or
> add a dg-warning. For the already-implemented obsolescent warnings I
> changed the message to unify it with the new ones, so I also had to
> change some dg-warnings in the testsuite.
> 

Janus,

I think this the wrong approach.
You should _NOT_ couple these Warnings with -std=legacy.

The description in the manual of -std=legacy is:
The `legacy' value is equivalent (to `gnu') but without the warnings for obsolete extensions.

Note the word "extensions", i.e. support for some old (vendor/compiler)
extensions not supported by a particular standards version. That's how 
I read this, at least.

For me there is a huge difference beween "extension" and 
"language feature", and between "supported", "obsolescent" and "deleted".

As long as a feature is supported by a standard, you should not
get warnings with default compiler settings, at least for things which
are only a style matter and do not bear the danger of unintentional
coding errors.

In the "legacy" compartment some obscure features are included which
very few people want to use, e.g. real do loops or implicit
integer/logical conversion.

So it would be very sad if all people wanting to compile old fortran
code are forced to use "legacy", and load the associated crap with it.

And if you think you can _ever_ delete these features from gfortran,
I think you are mistaken. Gfortran will have to support these
features even if they are _deleted_ from the fortran standards.


So could you couple these warnings with -Wextra, or even with
-Wall, or introduce a new "-std=" category, this would be great.

But to couple these (standards conforming) style matters with legacy
crap is simply not good, IMO.


Thanks, Manfred


> Regtested on x86_64-unknown-linux-gnu. Ok for trunk?
> 
> Cheers,
> Janus
> 
> 
> 2009-08-01  Janus Weil  <janus@gcc.gnu.org>
> 
> 	PR fortran/40881
> 	* decl.c (match_char_length): Warn about old-style character length
> 	declarations.
> 	* match.c (match_arithmetic_if,gfc_match_if): Modify warning message
> 	for arithmetic if.
> 	(gfc_match_goto): Warn about computed gotos.
> 	(gfc_match_return): Warn about alternate return.
> 	(gfc_match_st_function): Warn about statement functions.
> 	* resolve.c (resolve_fl_procedure): Modify warning message for
> 	assumed-length character functions.
> 
> 
> 2009-08-01  Janus Weil  <janus@gcc.gnu.org>
> 
> 	PR fortran/40881
> 	* gfortran.dg/aliasing_dummy_1.f90: Add -std=legacy.
> 	* gfortran.dg/altreturn_3.f90: Ditto.
> 	* gfortran.dg/altreturn_5.f90: Ditto.
> 	* gfortran.dg/altreturn_6.f90: Ditto.
> 	* gfortran.dg/altreturn_7.f90: Ditto.
> 	* gfortran.dg/array_constructor_13.f90: Ditto.
> 	* gfortran.dg/arrayio_7.f90: Ditto.
> 	* gfortran.dg/arrayio_8.f90: Ditto.
> 	* gfortran.dg/assumed_charlen_function_3.f90: Modified warning message.
> 	* gfortran.dg/assumed_charlen_function_4.f90: Add -std=legacy.
> 	* gfortran.dg/assumed_charlen_function_5.f90: Modified warning message.
> 	* gfortran.dg/backspace_8.f: Add -std=legacy.
> 	* gfortran.dg/backspace_9.f: Ditto.
> 	* gfortran.dg/char_comparison_1.f: Ditto.
> 	* gfortran.dg/char_decl_1.f90: Ditto.
> 	* gfortran.dg/char_initialiser_actual.f90: Ditto.
> 	* gfortran.dg/char_pointer_assign.f90: Ditto.
> 	* gfortran.dg/char_pointer_dependency.f90: Ditto.
> 	* gfortran.dg/char_pointer_dummy.f90: Ditto.
> 	* gfortran.dg/char_pointer_func.f90: Ditto.
> 	* gfortran.dg/common_8.f90: Ditto.
> 	* gfortran.dg/constant_substring.f: Ditto.
> 	* gfortran.dg/data_char_2.f90: Ditto.
> 	* gfortran.dg/der_array_io_1.f90: Ditto.
> 	* gfortran.dg/der_array_io_2.f90: Ditto.
> 	* gfortran.dg/der_array_io_3.f90: Ditto.
> 	* gfortran.dg/der_io_3.f90: Ditto.
> 	* gfortran.dg/dev_null.F90: Ditto.
> 	* gfortran.dg/direct_io_2.f90: Ditto.
> 	* gfortran.dg/do_iterator_2.f90: Ditto.
> 	* gfortran.dg/e_d_fmt.f90: Ditto.
> 	* gfortran.dg/empty_format_1.f90: Ditto.
> 	* gfortran.dg/entry_17.f90: Modified warning message.
> 	* gfortran.dg/entry_7.f90: Add -std=legacy.
> 	* gfortran.dg/eor_1.f90: Ditto.
> 	* gfortran.dg/equiv_2.f90: Ditto.
> 	* gfortran.dg/equiv_constraint_2.f90: Use new-style character length.
> 	* gfortran.dg/equiv_substr.f90: Add -std=legacy.
> 	* gfortran.dg/extended_char_comparison_1.f: Ditto.
> 	* gfortran.dg/fmt_bz_bn_err.f: Ditto.
> 	* gfortran.dg/fmt_error_2.f90: Ditto.
> 	* gfortran.dg/fmt_read_bz_bn.f90: Ditto.
> 	* gfortran.dg/fmt_tl.f: Ditto.
> 	* gfortran.dg/fmt_white.f: Ditto.
> 	* gfortran.dg/func_derived_1.f90: Ditto.
> 	* gfortran.dg/g77_intrinsics_funcs.f: Ditto.
> 	* gfortran.dg/g77_intrinsics_sub.f: Ditto.
> 	* gfortran.dg/global_references_2.f90: Ditto.
> 	* gfortran.dg/hollerith_1.f90: Ditto.
> 	* gfortran.dg/hollerith.f90: Use new-style character length.
> 	* gfortran.dg/hollerith_f95.f90: Ditto.
> 	* gfortran.dg/ichar_1.f90: Add -std=legacy.
> 	* gfortran.dg/implicit_6.f90: Ditto.
> 	* gfortran.dg/implicit_9.f90: Ditto.
> 	* gfortran.dg/inquire_13.f90: Ditto.
> 	* gfortran.dg/inquire_5.f90: Ditto.
> 	* gfortran.dg/inquire_6.f90: Ditto.
> 	* gfortran.dg/inquire.f90: Ditto.
> 	* gfortran.dg/io_constraints_1.f90: Use new-style character length.
> 	* gfortran.dg/io_constraints_2.f90: Ditto.
> 	* gfortran.dg/list_read_2.f90: Add -std=legacy.
> 	* gfortran.dg/loc_2.f90: Ditto.
> 	* gfortran.dg/logical_1.f90: Ditto.
> 	* gfortran.dg/longline.f: Ditto.
> 	* gfortran.dg/merge_char_1.f90: Ditto.
> 	* gfortran.dg/namelist_12.f: Ditto.
> 	* gfortran.dg/namelist_14.f90: Ditto.
> 	* gfortran.dg/namelist_18.f90: Ditto.
> 	* gfortran.dg/namelist_19.f90: Ditto.
> 	* gfortran.dg/namelist_21.f90: Ditto.
> 	* gfortran.dg/namelist_22.f90: Ditto.
> 	* gfortran.dg/namelist_37.f90: Ditto.
> 	* gfortran.dg/namelist_54.f90: Ditto.
> 	* gfortran.dg/namelist_55.f90: Ditto.
> 	* gfortran.dg/namelist_empty.f90: Ditto.
> 	* gfortran.dg/namelist_use.f90: Use new-style character length.
> 	* gfortran.dg/namelist_use_only.f90: Add -std=legacy.
> 	* gfortran.dg/nested_modules_4.f90: Ditto.
> 	* gfortran.dg/nested_modules_5.f90: Ditto.
> 	* gfortran.dg/open-options-blanks.f: Ditto.
> 	* gfortran.dg/output_exponents_1.f90: Ditto.
> 	* gfortran.dg/parens_5.f90: Ditto.
> 	* gfortran.dg/parens_6.f90: Ditto.
> 	* gfortran.dg/parent_result_ref_2.f90: Modified warning message.
> 	* gfortran.dg/pointer_function_actual_1.f90: Add -std=legacy.
> 	* gfortran.dg/pr15129.f90: Ditto.
> 	* gfortran.dg/pr15332.f: Ditto.
> 	* gfortran.dg/pr16597.f90: Ditto.
> 	* gfortran.dg/pr17143.f90: Ditto.
> 	* gfortran.dg/pr17164.f90: Ditto.
> 	* gfortran.dg/pr17229.f: Modified warning message.
> 	* gfortran.dg/pr18210.f90: Add -std=legacy.
> 	* gfortran.dg/pr19155.f: Ditto.
> 	* gfortran.dg/pr20086.f90: Ditto.
> 	* gfortran.dg/pr20124.f90: Ditto.
> 	* gfortran.dg/pr20755.f: Ditto.
> 	* gfortran.dg/pr20865.f90: Ditto.
> 	* gfortran.dg/pr20950.f: Ditto.
> 	* gfortran.dg/pr21730.f: Ditto.
> 	* gfortran.dg/pr22491.f: Ditto.
> 	* gfortran.dg/pr29713.f90: Ditto.
> 	* gfortran.dg/print_parentheses_1.f: Ditto.
> 	* gfortran.dg/print_parentheses_2.f90: Ditto.
> 	* gfortran.dg/proc_assign_1.f90: Ditto.
> 	* gfortran.dg/proc_decl_1.f90: Ditto.
> 	* gfortran.dg/proc_ptr_17.f90: Add dg-warning.
> 	* gfortran.dg/read_eor.f90: : Add -std=legacy.
> 	* gfortran.dg/read_float_1.f90: Ditto.
> 	* gfortran.dg/read_logical.f90: Ditto.
> 	* gfortran.dg/recursive_statement_functions.f90: Ditto.
> 	* gfortran.dg/return_1.f90: Ditto.
> 	* gfortran.dg/rewind_1.f90: Ditto.
> 	* gfortran.dg/runtime_warning_1.f90: Use new-style character length.
> 	* gfortran.dg/scalar_return_1.f90: Add -std=legacy.
> 	* gfortran.dg/stfunc_1.f90: Ditto.
> 	* gfortran.dg/stfunc_3.f90: Ditto.
> 	* gfortran.dg/stfunc_4.f90: Ditto.
> 	* gfortran.dg/stfunc_6.f90: Ditto.
> 	* gfortran.dg/streamio_2.f90: Ditto.
> 	* gfortran.dg/string_ctor_1.f90: Ditto.
> 	* gfortran.dg/string_null_compare_1.f: Ditto.
> 	* gfortran.dg/substr_6.f90: Ditto.
> 	* gfortran.dg/tl_editing.f90: Ditto.
> 	* gfortran.dg/unf_io_convert_1.f90: Use new-style character length.
> 	* gfortran.dg/warnings_are_errors_1.f90: Modified warning message.
> 	* gfortran.dg/x_slash_1.f: Add -std=legacy.
> 	* gfortran.dg/g77/1832.f: Ditto.
> 	* gfortran.dg/g77/19981216-0.f Ditto.
> 	* gfortran.dg/g77/19990525-0.f: Ditto.
> 	* gfortran.dg/g77/19990826-2.f: Ditto.
> 	* gfortran.dg/g77/20000630-2.f: Ditto.
> 	* gfortran.dg/g77/20010116.f: Ditto.
> 	* gfortran.dg/g77/20010519-1.f: Use new-style character length.
> 	* gfortran.dg/g77/980419-2.f: Add -std=legacy.
> 	* gfortran.dg/g77/980520-1.f: Ditto.
> 	* gfortran.dg/g77/check0.f: Ditto.
> 	* gfortran.dg/g77/cpp3.F: Ditto.
> 	* gfortran.dg/g77/cpp4.F: Use new-style character length.
> 	* gfortran.dg/g77/f77-edit-i-in.f: Add -std=legacy.
> 	* gfortran.dg/g77/f77-edit-t-in.f: Ditto.
> 	* gfortran.dg/g77/short.f: Ditto.

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