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c++: Fix ICE with structured binding initialized to incomplete array [PR97878]

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We ICE on the following testcase, for incomplete array a on auto [b] { a }; without
giving any kind of diagnostics, with auto [c] = a; during error-recovery.
The problem is that we get too far through check_initializer and e.g.
store_init_value -> constexpr stuff can't deal with incomplete array types.

As the type of the structured binding artificial variable is always deduced,
I think it is easiest to diagnose this early, even if they have array types
we'll need their deduced type to be complete rather than just its element
type.

2021-02-05  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2021-02-05 10:22:07 +01:00
parent d9bb52150d
commit b229baa75c
2 changed files with 30 additions and 0 deletions
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13
gcc/cp/decl.c
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@ -6768,6 +6768,19 @@ check_array_initializer (tree decl, tree type, tree init)
{
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 %qT", 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. */

17
gcc/testsuite/g++.dg/cpp1z/decomp54.C Normal file
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@ -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 }