Re: [PATCH] c++ modules: partial variable template specializations [PR106826]

[Nathan Sidwell <nathan@acm.org>]

On 9/21/22 12:16, Patrick Palka wrote:
> With partial variable template specializations, it looks like we
> stream the VAR_DECL (i.e. the DECL_TEMPLATE_RESULT of the corresponding
> TEMPLATE_DECL) since process_partial_specialization adds it to the
> specializations table, but end up never streaming the corresponding
> TEMPLATE_DECL itself that appears only in the primary template's
> DECL_TEMPLATE_SPECIALIZATIONS list, which leads to the list being
> incomplete on stream-in.
> 
> The modules machinery already has special logic for streaming partial
> specializations of class templates; this patch generalizes it to handle
> those of variable templates as well.

looks good, I didn't realize template vars had partial specializations.

> 
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
> 
> 	PR c++/106826
> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc (trees_out::decl_value): Use get_template_info in
> 	the MK_partial case.
> 	(trees_out::key_mergeable): Likewise.
> 	(trees_in::key_mergeable): Likewise.
> 	(has_definition): Consider DECL_INITIAL of a partial variable
> 	template specialization.
> 	(depset::hash::make_dependency): Introduce a dependency of
> 	partial variable template specializations too.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/partial-2_a.C: New test.
> 	* g++.dg/modules/partial-2_b.C: New test.
> ---
>   gcc/cp/module.cc                           | 32 +++++++++-------
>   gcc/testsuite/g++.dg/modules/partial-2_a.C | 43 ++++++++++++++++++++++
>   gcc/testsuite/g++.dg/modules/partial-2_b.C | 21 +++++++++++
>   3 files changed, 82 insertions(+), 14 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/partial-2_a.C
>   create mode 100644 gcc/testsuite/g++.dg/modules/partial-2_b.C
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 9a9ef4e3332..334bde99b0f 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -7789,8 +7789,9 @@ trees_out::decl_value (tree decl, depset *dep)
>   	    }
>   	  else
>   	    {
> -	      tree_node (CLASSTYPE_TI_TEMPLATE (TREE_TYPE (inner)));
> -	      tree_node (CLASSTYPE_TI_ARGS (TREE_TYPE (inner)));
> +	      tree ti = get_template_info (inner);
> +	      tree_node (TI_TEMPLATE (ti));
> +	      tree_node (TI_ARGS (ti));
>   	    }
>   	}
>         tree_node (get_constraints (decl));
> @@ -10626,8 +10627,9 @@ trees_out::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
>   	case MK_partial:
>   	  {
>   	    key.constraints = get_constraints (inner);
> -	    key.ret = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (inner));
> -	    key.args = CLASSTYPE_TI_ARGS (TREE_TYPE (inner));
> +	    tree ti = get_template_info (inner);
> +	    key.ret = TI_TEMPLATE (ti);
> +	    key.args = TI_ARGS (ti);
>   	  }
>   	  break;
>   	}
> @@ -10866,8 +10868,8 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
>   	       spec; spec = TREE_CHAIN (spec))
>   	    {
>   	      tree tmpl = TREE_VALUE (spec);
> -	      if (template_args_equal (key.args,
> -				       CLASSTYPE_TI_ARGS (TREE_TYPE (tmpl)))
> +	      tree ti = get_template_info (tmpl);
> +	      if (template_args_equal (key.args, TI_ARGS (ti))
>   		  && cp_tree_equal (key.constraints,
>   				    get_constraints
>   				    (DECL_TEMPLATE_RESULT (tmpl))))
> @@ -11381,8 +11383,7 @@ has_definition (tree decl)
>   
>       case VAR_DECL:
>         if (DECL_LANG_SPECIFIC (decl)
> -	  && DECL_TEMPLATE_INFO (decl)
> -	  && DECL_USE_TEMPLATE (decl) < 2)
> +	  && DECL_TEMPLATE_INFO (decl))
>   	return DECL_INITIAL (decl);
>         else
>   	{
> @@ -12498,11 +12499,14 @@ depset::hash::make_dependency (tree decl, entity_kind ek)
>   
>     if (!dep)
>       {
> -      if (DECL_IMPLICIT_TYPEDEF_P (decl)
> -	  /* ... not an enum, for instance.  */
> -	  && RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
> -	  && TYPE_LANG_SPECIFIC (TREE_TYPE (decl))
> -	  && CLASSTYPE_USE_TEMPLATE (TREE_TYPE (decl)) == 2)
> +      if ((DECL_IMPLICIT_TYPEDEF_P (decl)
> +	   /* ... not an enum, for instance.  */
> +	   && RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
> +	   && TYPE_LANG_SPECIFIC (TREE_TYPE (decl))
> +	   && CLASSTYPE_USE_TEMPLATE (TREE_TYPE (decl)) == 2)
> +	  || (VAR_P (decl)
> +	      && DECL_LANG_SPECIFIC (decl)
> +	      && DECL_USE_TEMPLATE (decl) == 2))
>   	{
>   	  /* A partial or explicit specialization. Partial
>   	     specializations might not be in the hash table, because
> @@ -12515,7 +12519,7 @@ depset::hash::make_dependency (tree decl, entity_kind ek)
>   	     dep_hash, and then convert the dep we just found into a
>   	     redirect.  */
>   
> -	  tree ti = TYPE_TEMPLATE_INFO (TREE_TYPE (decl));
> +	  tree ti = get_template_info (decl);
>   	  tree tmpl = TI_TEMPLATE (ti);
>   	  tree partial = NULL_TREE;
>   	  for (tree spec = DECL_TEMPLATE_SPECIALIZATIONS (tmpl);
> diff --git a/gcc/testsuite/g++.dg/modules/partial-2_a.C b/gcc/testsuite/g++.dg/modules/partial-2_a.C
> new file mode 100644
> index 00000000000..2681bb59ce8
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/partial-2_a.C
> @@ -0,0 +1,43 @@
> +// PR c++/106826
> +// { dg-additional-options -fmodules-ts }
> +// { dg-module-cmi pr106826 }
> +export module pr106826;
> +
> +template<class T> constexpr bool is_reference_v = false;
> +template<class T> constexpr bool is_reference_v<T&> = true;
> +template<class T> constexpr bool is_reference_v<T&&> = true;
> +
> +struct A {
> +  template<class T> static constexpr bool is_reference_v = false;
> +};
> +
> +template<class T> constexpr bool A::is_reference_v<T&> = true;
> +template<class T> constexpr bool A::is_reference_v<T&&> = true;
> +
> +#if __cpp_concepts
> +namespace concepts {
> +  template<class T> bool is_reference_v;
> +
> +  template<class T> requires __is_same(T, T&)
> +  constexpr bool is_reference_v<T> = true;
> +
> +  template<class T> requires __is_same(T, T&&) && (!__is_same(T, T&))
> +  constexpr bool is_reference_v<T> = true;
> +
> +  template<class T> requires (!__is_same(T, T&)) && (!__is_same(T, T&&))
> +  constexpr bool is_reference_v<T> = false;
> +
> +  struct A {
> +    template<class T> static bool is_reference_v;
> +  };
> +
> +  template<class T> requires __is_same(T, T&)
> +  constexpr bool A::is_reference_v<T> = true;
> +
> +  template<class T> requires __is_same(T, T&&) && (!__is_same(T, T&))
> +  constexpr bool A::is_reference_v<T> = true;
> +
> +  template<class T> requires (!__is_same(T, T&)) && (!__is_same(T, T&&))
> +  constexpr bool A::is_reference_v<T> = false;
> +}
> +#endif
> diff --git a/gcc/testsuite/g++.dg/modules/partial-2_b.C b/gcc/testsuite/g++.dg/modules/partial-2_b.C
> new file mode 100644
> index 00000000000..0af41ef5e5e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/partial-2_b.C
> @@ -0,0 +1,21 @@
> +// PR c++/106826
> +// { dg-additional-options -fmodules-ts }
> +module pr106826;
> +
> +static_assert(is_reference_v<int&>);
> +static_assert(is_reference_v<int&&>);
> +static_assert(!is_reference_v<int>);
> +
> +static_assert(A::is_reference_v<long&>);
> +static_assert(A::is_reference_v<long&&>);
> +static_assert(!A::is_reference_v<long>);
> +
> +#if __cpp_concepts
> +static_assert(concepts::is_reference_v<char&>);
> +static_assert(concepts::is_reference_v<char&&>);
> +static_assert(!concepts::is_reference_v<char>);
> +
> +static_assert(concepts::A::is_reference_v<bool&>);
> +static_assert(concepts::A::is_reference_v<bool&&>);
> +static_assert(!concepts::A::is_reference_v<bool>);
> +#endif

-- 
Nathan Sidwell