diff mbox series

c++: using non-dep array variable of unknown bound [PR115358]

Message ID 20240625010027.124995-1-ppalka@redhat.com
State New
Headers show
Series c++: using non-dep array variable of unknown bound [PR115358] | expand

Commit Message

Patrick Palka June 25, 2024, 1 a.m. UTC 
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
for trunk?  This fixes PR115358 whose testcase used a constexpr static
array variable, but it seems the general issue is not specific to
constexpr as illustrated by the below testcase.  Note that Clang
currently rejects the testcase for a similar reason to GCC...

-- >8 --

For a non-dependent array variable of unknown bound, it seems we need to
try instantiating its definition upon use in a template context for sake
of proper checking and typing of its expression context.  This seems
analogous to deducing the return type of a function which is similarly
done upon first use even in a template context.

	PR c++/115358

gcc/cp/ChangeLog:

	* decl2.cc (mark_used): Call maybe_instantiate_decl for an array
	variable with unknown bound.
	* semantics.cc (finish_decltype_type): Remove now redundant
	handling of array variables with unknown bound.
	* typeck.cc (cxx_sizeof_expr): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/template/array37.C: New test.
---
 gcc/cp/decl2.cc                         |  2 ++
 gcc/cp/semantics.cc                     |  7 -------
 gcc/cp/typeck.cc                        |  7 -------
 gcc/testsuite/g++.dg/template/array37.C | 16 ++++++++++++++++
 4 files changed, 18 insertions(+), 14 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/array37.C

Comments

Jason Merrill June 25, 2024, 1:44 a.m. UTC | #1 
On 6/24/24 21:00, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
> for trunk?  This fixes PR115358 whose testcase used a constexpr static
> array variable, but it seems the general issue is not specific to
> constexpr as illustrated by the below testcase.  Note that Clang
> currently rejects the testcase for a similar reason to GCC...

OK.

> -- >8 --
> 
> For a non-dependent array variable of unknown bound, it seems we need to
> try instantiating its definition upon use in a template context for sake
> of proper checking and typing of its expression context.  This seems
> analogous to deducing the return type of a function which is similarly
> done upon first use even in a template context.
> 
> 	PR c++/115358
> 
> gcc/cp/ChangeLog:
> 
> 	* decl2.cc (mark_used): Call maybe_instantiate_decl for an array
> 	variable with unknown bound.
> 	* semantics.cc (finish_decltype_type): Remove now redundant
> 	handling of array variables with unknown bound.
> 	* typeck.cc (cxx_sizeof_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/array37.C: New test.
> ---
>   gcc/cp/decl2.cc                         |  2 ++
>   gcc/cp/semantics.cc                     |  7 -------
>   gcc/cp/typeck.cc                        |  7 -------
>   gcc/testsuite/g++.dg/template/array37.C | 16 ++++++++++++++++
>   4 files changed, 18 insertions(+), 14 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/array37.C
> 
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index 6c3ef60d51f..cdd2b8aada2 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -6001,6 +6001,8 @@ mark_used (tree decl, tsubst_flags_t complain /* = tf_warning_or_error */)
>        find out its type.  For OpenMP user defined reductions, we need them
>        instantiated for reduction clauses which inline them by hand directly.  */
>     if (undeduced_auto_decl (decl)
> +      || (VAR_P (decl)
> +	  && VAR_HAD_UNKNOWN_BOUND (decl))
>         || (TREE_CODE (decl) == FUNCTION_DECL
>   	  && DECL_OMP_DECLARE_REDUCTION_P (decl)))
>       maybe_instantiate_decl (decl);
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index b4f626924af..3247521e03e 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12002,13 +12002,6 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
>         return error_mark_node;
>       }
>   
> -  /* To get the size of a static data member declared as an array of
> -     unknown bound, we need to instantiate it.  */
> -  if (VAR_P (expr)
> -      && VAR_HAD_UNKNOWN_BOUND (expr)
> -      && DECL_TEMPLATE_INSTANTIATION (expr))
> -    instantiate_decl (expr, /*defer_ok*/true, /*expl_inst_mem*/false);
> -
>     if (id_expression_or_member_access_p)
>       {
>         /* If e is an id-expression or a class member access (5.2.5
> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> index 5970ac3d398..9297948cfa5 100644
> --- a/gcc/cp/typeck.cc
> +++ b/gcc/cp/typeck.cc
> @@ -2127,13 +2127,6 @@ cxx_sizeof_expr (location_t loc, tree e, tsubst_flags_t complain)
>     location_t e_loc = cp_expr_loc_or_loc (e, loc);
>     STRIP_ANY_LOCATION_WRAPPER (e);
>   
> -  /* To get the size of a static data member declared as an array of
> -     unknown bound, we need to instantiate it.  */
> -  if (VAR_P (e)
> -      && VAR_HAD_UNKNOWN_BOUND (e)
> -      && DECL_TEMPLATE_INSTANTIATION (e))
> -    instantiate_decl (e, /*defer_ok*/true, /*expl_inst_mem*/false);
> -
>     if (TREE_CODE (e) == PARM_DECL
>         && DECL_ARRAY_PARAMETER_P (e)
>         && (complain & tf_warning))
> diff --git a/gcc/testsuite/g++.dg/template/array37.C b/gcc/testsuite/g++.dg/template/array37.C
> new file mode 100644
> index 00000000000..ed03b955f05
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/array37.C
> @@ -0,0 +1,16 @@
> +// PR c++/115358
> +// { dg-do compile { target c++14 } }
> +
> +template<class T>
> +struct A { static int STR[]; };
> +
> +template<class T>
> +int A<T>::STR[] = {1,2,3};
> +
> +void g(int(&)[3]);
> +
> +int main() {
> +  [](auto) {
> +    g(A<int>::STR); // { dg-bogus "int []" }
> +  };
> +}
diff mbox series

Patch

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 6c3ef60d51f..cdd2b8aada2 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -6001,6 +6001,8 @@  mark_used (tree decl, tsubst_flags_t complain /* = tf_warning_or_error */)
      find out its type.  For OpenMP user defined reductions, we need them
      instantiated for reduction clauses which inline them by hand directly.  */
   if (undeduced_auto_decl (decl)
+      || (VAR_P (decl)
+	  && VAR_HAD_UNKNOWN_BOUND (decl))
       || (TREE_CODE (decl) == FUNCTION_DECL
 	  && DECL_OMP_DECLARE_REDUCTION_P (decl)))
     maybe_instantiate_decl (decl);
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index b4f626924af..3247521e03e 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12002,13 +12002,6 @@  finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
       return error_mark_node;
     }
 
-  /* To get the size of a static data member declared as an array of
-     unknown bound, we need to instantiate it.  */
-  if (VAR_P (expr)
-      && VAR_HAD_UNKNOWN_BOUND (expr)
-      && DECL_TEMPLATE_INSTANTIATION (expr))
-    instantiate_decl (expr, /*defer_ok*/true, /*expl_inst_mem*/false);
-
   if (id_expression_or_member_access_p)
     {
       /* If e is an id-expression or a class member access (5.2.5
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 5970ac3d398..9297948cfa5 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -2127,13 +2127,6 @@  cxx_sizeof_expr (location_t loc, tree e, tsubst_flags_t complain)
   location_t e_loc = cp_expr_loc_or_loc (e, loc);
   STRIP_ANY_LOCATION_WRAPPER (e);
 
-  /* To get the size of a static data member declared as an array of
-     unknown bound, we need to instantiate it.  */
-  if (VAR_P (e)
-      && VAR_HAD_UNKNOWN_BOUND (e)
-      && DECL_TEMPLATE_INSTANTIATION (e))
-    instantiate_decl (e, /*defer_ok*/true, /*expl_inst_mem*/false);
-
   if (TREE_CODE (e) == PARM_DECL
       && DECL_ARRAY_PARAMETER_P (e)
       && (complain & tf_warning))
diff --git a/gcc/testsuite/g++.dg/template/array37.C b/gcc/testsuite/g++.dg/template/array37.C
new file mode 100644
index 00000000000..ed03b955f05
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/array37.C
@@ -0,0 +1,16 @@ 
+// PR c++/115358
+// { dg-do compile { target c++14 } }
+
+template<class T>
+struct A { static int STR[]; };
+
+template<class T>
+int A<T>::STR[] = {1,2,3};
+
+void g(int(&)[3]);
+
+int main() {
+  [](auto) {
+    g(A<int>::STR); // { dg-bogus "int []" }
+  };
+}