Re: [PATCH] c++/modules: relax diagnostic about GMF contents

[Patrick Palka <ppalka@redhat.com>]

On Thu, 15 Feb 2024, Patrick Palka wrote:

> On Thu, 15 Feb 2024, Jason Merrill wrote:
> 
> > On 2/15/24 16:10, Patrick Palka wrote:
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > > OK for trunk?
> > > 
> > > -- >8 --
> > > 
> > > Issuing a hard error when the GMF doesn't contain preprocessing
> > > directives is inconvenient for automated testcase reduction via cvise.
> > > This patch relaxes this diagnostic into a pedwarn.
> > > 
> > > gcc/cp/ChangeLog:
> > > 
> > > 	* parser.cc (cp_parser_translation_unit): Relax GMF contents
> > > 	error into a pedwarn.
> > > 
> > > gcc/testsuite/ChangeLog:
> > > 
> > > 	* g++.dg/modules/friend-6_a.C: Remove now unnecessary
> > > 	preprocessing directives from GMF.
> > > ---
> > >   gcc/cp/parser.cc                          | 6 +++---
> > >   gcc/testsuite/g++.dg/modules/friend-6_a.C | 2 --
> > >   2 files changed, 3 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> > > index 9d0914435fb..e60f0425035 100644
> > > --- a/gcc/cp/parser.cc
> > > +++ b/gcc/cp/parser.cc
> > > @@ -5253,9 +5253,9 @@ cp_parser_translation_unit (cp_parser* parser)
> > >   	      if (!warned)
> > >   		{
> > >   		  warned = true;
> > > -		  error_at (token->location,
> > > -			    "global module fragment contents must be"
> > > -			    " from preprocessor inclusion");
> > > +		  pedwarn (token->location, OPT_Wpedantic,
> > > +			   "global module fragment contents must be"
> > > +			   " from preprocessor inclusion");
> > 
> > Relaxing to pedwarn is fine, but I think it should be on by default, not just
> > with -pedantic.  So it should get a new option.
> 
> Ah, like so?  I'm not sure about naming the option Wmodules-gmf-contents
> vs just Wgmf-contents, or something else...

Ping.

> 
> -- >8 --
> 
> Subject: [PATCH] c++/modules: relax diagnostic about GMF contents
> 
> Issuing a hard error when the GMF doesn't contain preprocessing
> directives is inconvenient for automated testcase reduction via cvise.
> This patch relaxes this diagnostic into a pedwarn that can be disabled
> with -Wno-modules-gmf-contents.
> 
> gcc/c-family/ChangeLog:
> 
> 	* c.opt (Wmodules-gmf-contents): New warning.
> 
> gcc/cp/ChangeLog:
> 
> 	* parser.cc (cp_parser_translation_unit): Relax GMF contents
> 	error into a pedwarn.
> 
> gcc/ChangeLog:
> 
> 	* doc/invoke.texi (-Wno-modules-gmf-contents): Document.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/friend-6_a.C: Pass -Wno-modules-gmf-contents
> 	instead of -Wno-pedantic.  Remove now unnecessary preprocessing
> 	directives from GMF.
> ---
>  gcc/c-family/c.opt                        | 4 ++++
>  gcc/cp/parser.cc                          | 6 +++---
>  gcc/doc/invoke.texi                       | 7 +++++++
>  gcc/testsuite/g++.dg/modules/friend-6_a.C | 4 +---
>  4 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index b7a4a1a68e3..6d5f3199b33 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -993,6 +993,10 @@ Wmissing-variable-declarations
>  C ObjC Var(warn_missing_variable_declarations) Warning
>  Warn about global variables without previous declarations.
>  
> +Wmodules-gmf-contents
> +C++ ObjC++ Var(warn_modules_gmf_contents) Warning Init(1)
> +Warn about the global module fragment not containing only preprocessing directives.
> +
>  Wmudflap
>  C ObjC C++ ObjC++ WarnRemoved
>  
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 9d0914435fb..eb709fc9e38 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -5253,9 +5253,9 @@ cp_parser_translation_unit (cp_parser* parser)
>  	      if (!warned)
>  		{
>  		  warned = true;
> -		  error_at (token->location,
> -			    "global module fragment contents must be"
> -			    " from preprocessor inclusion");
> +		  pedwarn (token->location, OPT_Wmodules_gmf_contents,
> +			   "global module fragment contents must be"
> +			   " from preprocessor inclusion");
>  		}
>  	    }
>  	}
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 511114cde59..e27fda88bc4 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -261,6 +261,7 @@ in the following sections.
>  -Winvalid-constexpr -Winvalid-imported-macros
>  -Wno-invalid-offsetof  -Wno-literal-suffix
>  -Wmismatched-new-delete -Wmismatched-tags
> +-Wno-modules-gmf-contents
>  -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing
>  -Wnoexcept  -Wnoexcept-type  -Wnon-virtual-dtor
>  -Wpessimizing-move  -Wno-placement-new  -Wplacement-new=@var{n}
> @@ -4568,6 +4569,12 @@ unresolved references due to the difference in the mangling of symbols
>  declared with different class-keys.  The option can be used either on its
>  own or in conjunction with @option{-Wredundant-tags}.
>  
> +@opindex Wno-modules-gmf-contents
> +@opindex Wmodules-gmf-contents
> +@item -Wno-modules-gmf-contents @r{(C++ and Objective-C++ only)}
> +Disable the diagnostic for when the global module fragment of a module
> +unit does not consist only of preprocessor directives.
> +
>  @opindex Wmultiple-inheritance
>  @opindex Wno-multiple-inheritance
>  @item -Wmultiple-inheritance @r{(C++ and Objective-C++ only)}
> diff --git a/gcc/testsuite/g++.dg/modules/friend-6_a.C b/gcc/testsuite/g++.dg/modules/friend-6_a.C
> index 7493e8f262f..429fb460eea 100644
> --- a/gcc/testsuite/g++.dg/modules/friend-6_a.C
> +++ b/gcc/testsuite/g++.dg/modules/friend-6_a.C
> @@ -1,11 +1,9 @@
> -// { dg-additional-options "-fmodules-ts -Wno-pedantic" }
> +// { dg-additional-options "-fmodules-ts -Wno-modules-gmf-contents" }
>  // { dg-module-cmi friend_6 }
>  
>  module;
> -# 1 "" 1
>  template <typename> struct Trans_NS___cxx11_basic_string {
>    template <typename> friend class basic_stringbuf;
>  };
>  template struct Trans_NS___cxx11_basic_string<char>;
> -# 6 "" 2
>  export module friend_6;
> -- 
> 2.44.0.rc1.15.g4fc51f00ef
> 
>