On Thu, Feb 04, 2021 at 11:03:10AM -0500, Jason Merrill wrote:
> > --- gcc/cp/decl.c.jj 2021-01-28 16:13:04.000000000 +0100
> > +++ gcc/cp/decl.c 2021-02-03 15:57:16.980557836 +0100
> > @@ -6837,7 +6837,8 @@ check_initializer (tree decl, tree init,
> > /* We will have already complained. */
> > return NULL_TREE;
> > - if (TREE_CODE (type) == ARRAY_TYPE)
> > + if (TREE_CODE (type) == ARRAY_TYPE
> > + && (!DECL_DECOMPOSITION_P (decl) || DECL_DECOMP_BASE (decl)))
>
> This needs a comment. Or handle this inside check_array_initializer, where
> we could give a more helpful diagnostic?
So like this?
2021-02-04 Jakub Jelinek <ja...@redhat.com>
PR c++/97878
* decl.c (check_array_initializer): For structured bindings, require
the array type to be complete.
* g++.dg/cpp1z/decomp54.C: New test.
--- gcc/cp/decl.c.jj 2021-02-03 17:13:58.567872007 +0100
+++ gcc/cp/decl.c 2021-02-04 18:42:35.347374198 +0100
@@ -6768,6 +6768,19 @@ check_array_initializer (tree decl, tree
{
tree element_type = TREE_TYPE (type);
+ /* Structured binding when initialized with an array type needs
+ to have complete type. */
+ if (decl
+ && DECL_DECOMPOSITION_P (decl)
+ && !DECL_DECOMP_BASE (decl)
+ && !COMPLETE_TYPE_P (type))
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "structured binding has incomplete type");
+ TREE_TYPE (decl) = error_mark_node;
+ return true;
+ }
+
/* The array type itself need not be complete, because the
initializer may tell us how many elements are in the array.
But, the elements of the array must be complete. */
--- gcc/testsuite/g++.dg/cpp1z/decomp54.C.jj 2021-02-04 18:33:34.829393825
+0100
+++ gcc/testsuite/g++.dg/cpp1z/decomp54.C 2021-02-04 18:33:34.829393825
+0100
@@ -0,0 +1,17 @@
+// PR c++/97878
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+extern int a[];
+auto [b] { a }; // { dg-error "has incomplete type" }
+ // { dg-warning "only available with" "" { target c++14_down }
.-1 }
+auto [c] = a; // { dg-error "has incomplete type" }
+ // { dg-warning "only available with" "" { target c++14_down }
.-1 }
+extern int d[0];
+auto [e] { d }; // { dg-error "too many initializers for" }
+ // { dg-error "1 name provided for structured binding" "" {
target *-*-* } .-1 }
+ // { dg-message "decomposes into 0 elements" "" { target *-*-*
} .-2 }
+ // { dg-warning "only available with" "" { target c++14_down }
.-3 }
+auto [f] = d; // { dg-error "1 name provided for structured binding" }
+ // { dg-message "decomposes into 0 elements" "" { target *-*-*
} .-1 }
+ // { dg-warning "only available with" "" { target c++14_down }
.-2 }
Jakub
