Re: [PATCH] c++: Check module attachment instead of purview when necessary [PR112631]

[Nathan Sidwell <nathan@acm.org>]

On 11/20/23 04:47, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu. I don't have write
> access.
> 
> -- >8 --
> 
> Block-scope declarations of functions or extern values are not allowed
> when attached to a named module. Similarly, class member functions are
> not inline if attached to a named module. However, in both these cases
> we currently only check if the declaration is within the module purview;
> it is possible for such a declaration to occur within the module purview
> but not be attached to a named module (e.g. in an 'extern "C++"' block).
> This patch makes the required adjustments.


Ah I'd been puzzling over the default inlinedness of  member-fns of block-scope 
structs.  Could you augment the testcase to make sure that's right too?

Something like:

// dg-module-do link
export module Mod;

export auto Get () {
   struct X { void Fn () {} };
   return X();
}


///
import Mod
void Frob () { Get().Fn(); }

> 
> 	PR c++/112631
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-tree.h (named_module_attach_p): New function.
> 	* decl.cc (start_decl): Use named_module_attach_p instead of
> 	named_module_purview_p.
> 	(grokmethod): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/pr112631.C: New test.
> ---
>   gcc/cp/cp-tree.h                        |  2 ++
>   gcc/cp/decl.cc                          | 10 +++++-----
>   gcc/testsuite/g++.dg/modules/pr112631.C |  8 ++++++++
>   3 files changed, 15 insertions(+), 5 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/pr112631.C
> 
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 7b0b7c6a17e..9a3981cef58 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7315,6 +7315,8 @@ inline bool module_attach_p ()
>   
>   inline bool named_module_purview_p ()
>   { return named_module_p () && module_purview_p (); }
> +inline bool named_module_attach_p ()
> +{ return named_module_p () && module_attach_p (); }
>   
>   /* We're currently exporting declarations.  */
>   inline bool module_exporting_p ()
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index e6f75d771e0..395f108aec7 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -5917,10 +5917,10 @@ start_decl (const cp_declarator *declarator,
>       {
>         /* A function-scope decl of some namespace-scope decl.  */
>         DECL_LOCAL_DECL_P (decl) = true;
> -      if (named_module_purview_p ())
> +      if (named_module_attach_p ())
>   	error_at (declarator->id_loc,
> -		  "block-scope extern declaration %q#D not permitted"
> -		  " in module purview", decl);
> +		  "block-scope extern declaration %q#D must not be"
> +		  " attached to a named module", decl);
>       }
>   
>     /* Enter this declaration into the symbol table.  Don't push the plain
> @@ -18513,10 +18513,10 @@ grokmethod (cp_decl_specifier_seq *declspecs,
>     check_template_shadow (fndecl);
>   
>     /* p1779 ABI-Isolation makes inline not a default for in-class
> -     definitions in named module purview.  If the user explicitly
> +     definitions attached to a named module.  If the user explicitly
>        made it inline, grokdeclarator will already have done the right
>        things.  */
> -  if ((!named_module_purview_p ()
> +  if ((!named_module_attach_p ()
>          || flag_module_implicit_inline
>         /* Lambda's operator function remains inline.  */
>          || LAMBDA_TYPE_P (DECL_CONTEXT (fndecl)))
> diff --git a/gcc/testsuite/g++.dg/modules/pr112631.C b/gcc/testsuite/g++.dg/modules/pr112631.C
> new file mode 100644
> index 00000000000..b5e81a1041b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/pr112631.C
> @@ -0,0 +1,8 @@
> +// { dg-additional-options "-fmodules-ts" }
> +// { dg-module-cmi bla }
> +
> +export module bla;
> +
> +extern "C++" inline void fun() {
> +  void oops();  // { dg-bogus "block-scope extern declaration" }
> +}

-- 
Nathan Sidwell