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c++: Handle structured bindings like anon unions in initializers [PR108474]

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As reported by Andrew Pinski, structured bindings (with the exception
of the ones using std::tuple_{size,element} and get which are really
standalone variables in addition to the binding one) also use
DECL_VALUE_EXPR and needs the same treatment in static initializers.

On Sun, Jan 22, 2023 at 07:19:07PM -0500, Jason Merrill wrote:
> Though, actually, why not instead fix expand_expr_real_1 (and staticp) to
> look through DECL_VALUE_EXPR?

Doing it when emitting the initializers seems to be too late to me,
we in various spots try to put parts of the static var DECL_INITIAL expressions
into the IL, or e.g. for varpool purposes remember which vars are referenced
there.

This patch moves it to record_reference, which is called from varpool_node::analyze
and so about the same time as gimplification of the bodies which also
replaces DECL_VALUE_EXPRs.

2023-01-24  Jakub Jelinek  <jakub@redhat.com>

	PR c++/108474
	* cp-gimplify.cc (cp_fold_r): Handle structured bindings
	vars like anon union artificial vars.

	* g++.dg/cpp1z/decomp57.C: New test.
	* g++.dg/cpp1z/decomp58.C: New test.

(cherry picked from commit b84e211157)
This commit is contained in:
Jakub Jelinek
2023-01-24 11:28:00 +01:00
parent a015ebe382
commit c153fb6a5b
3 changed files with 72 additions and 2 deletions
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8
gcc/cp/cp-gimplify.cc
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@@ -1006,8 +1006,12 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_)
case VAR_DECL:
/* In initializers replace anon union artificial VAR_DECLs
with their DECL_VALUE_EXPRs, as nothing will do it later. */
if (DECL_ANON_UNION_VAR_P (stmt) && !data->genericize)
with their DECL_VALUE_EXPRs, as nothing will do it later.
Ditto for structured bindings. */
if (!data->genericize
&& DECL_HAS_VALUE_EXPR_P (stmt)
&& (DECL_ANON_UNION_VAR_P (stmt)
|| (DECL_DECOMPOSITION_P (stmt) && DECL_DECOMP_BASE (stmt))))
{
*stmt_p = stmt = unshare_expr (DECL_VALUE_EXPR (stmt));
break;

27
gcc/testsuite/g++.dg/cpp1z/decomp57.C Normal file
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@@ -0,0 +1,27 @@
// PR c++/108474
// { dg-do link { target c++17 } }
struct T { int i, j; };
T h;
auto [i, j] = h;
int &r = i;
int s = i;
int *t = &i;
void
foo (int **p, int *q)
{
static int &u = i;
static int v = i;
static int *w = &i;
int &x = i;
int y = i;
int *z = &i;
*p = &i;
*q = i;
}
int
main ()
{
}

39
gcc/testsuite/g++.dg/cpp1z/decomp58.C Normal file
View File

@@ -0,0 +1,39 @@
// PR c++/108474
// { dg-do link { target c++17 } }
namespace std {
template <typename T> struct tuple_size;
template <int, typename> struct tuple_element;
}
struct A {
int i;
template <int I> int& get() { return i; }
};
template <> struct std::tuple_size <A> { static const int value = 2; };
template <int I> struct std::tuple_element <I, A> { using type = int; };
struct A a;
auto [i, j] = a;
int &r = i;
int s = i;
int *t = &i;
void
foo (int **p, int *q)
{
static int &u = i;
static int v = i;
static int *w = &i;
int &x = i;
int y = i;
int *z = &i;
*p = &i;
*q = i;
}
int
main ()
{
}