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PR c++/89089 - ICE with [[no_unique_address]]. 

In 89089, we were never actually setting DECL_SIZE on an empty data member,
because its type is a POD, so we didn't set it in the maybe-overlapping
section.  Fixed by also handling empty types there.

In 88865, we were failing to consider empty data members in
include_empty_classes.  Fixed by making end_of_class always include them.

While looking at these I noticed that the ABI says that a
potentially-overlapping data member makes its class non-layout-POD, and that
an empty data member doesn't prevent its class from being empty, so I've
implemented those points as well.

	PR c++/88865 - wrong layout with [[no_unique_address]].
	* class.c (check_field_decls): A potentially-overlapping field makes
	the class non-layout-POD, but not non-empty.
	(end_of_class): Always consider empty data members.
	(layout_class_type): Set DECL_SIZE for empty fields.

From-SVN: r268368
This commit is contained in:
Jason Merrill 2019-01-29 10:39:40 -05:00 committed by Jason Merrill
parent 6065f1c588
commit 7e574f68fa
5 changed files with 96 additions and 16 deletions
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9
gcc/cp/ChangeLog
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@ -1,3 +1,12 @@
2019-01-28 Jason Merrill <jason@redhat.com>
PR c++/89089 - ICE with [[no_unique_address]].
PR c++/88865 - wrong layout with [[no_unique_address]].
* class.c (check_field_decls): A potentially-overlapping field makes
the class non-layout-POD, but not non-empty.
(end_of_class): Always consider empty data members.
(layout_class_type): Set DECL_SIZE for empty fields.
2019-01-28 Marek Polacek <polacek@redhat.com>
PR c++/88358 - name wrongly treated as type.

48
gcc/cp/class.c
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@ -206,6 +206,7 @@ static int empty_base_at_nonzero_offset_p (tree, tree, splay_tree);
static tree end_of_base (tree);
static tree get_vcall_index (tree, tree);
static bool type_maybe_constexpr_default_constructor (tree);
static bool field_poverlapping_p (tree);
/* Return a COND_EXPR that executes TRUE_STMT if this execution of the
'structor is in charge of 'structing virtual bases, or FALSE_STMT
@ -3556,6 +3557,11 @@ check_field_decls (tree t, tree *access_decls,
/* We don't treat zero-width bitfields as making a class
non-empty. */
;
else if (field_poverlapping_p (x) && is_empty_class (type))
{
/* Empty data members also don't make a class non-empty. */
CLASSTYPE_CONTAINS_EMPTY_CLASS_P (t) = 1;
}
else
{
/* The class is non-empty. */
@ -3608,6 +3614,11 @@ check_field_decls (tree t, tree *access_decls,
to be allowed in POD structs. */
CLASSTYPE_NON_LAYOUT_POD_P (t) = 1;
if (field_poverlapping_p (x))
/* A potentially-overlapping non-static data member makes the class
non-layout-POD. */
CLASSTYPE_NON_LAYOUT_POD_P (t) = 1;
if (!std_layout_type_p (type))
CLASSTYPE_NON_STD_LAYOUT (t) = 1;
@ -5926,13 +5937,12 @@ end_of_base (tree binfo)
return size_binop (PLUS_EXPR, BINFO_OFFSET (binfo), size);
}
/* Returns the offset of the byte just past the end of the base class
with the highest offset in T. If INCLUDE_VIRTUALS_P is zero, then
only non-virtual bases are included. If INCLUDE_FIELDS_P is true,
then also consider non-static data members. */
/* Returns the offset of the byte just past the end of the base class or empty
data member with the highest offset in T. If INCLUDE_VIRTUALS_P is zero,
then only non-virtual bases are included. */
static tree
end_of_class (tree t, bool include_virtuals_p, bool include_fields_p = false)
end_of_class (tree t, bool include_virtuals_p)
{
tree result = size_zero_node;
vec<tree, va_gc> *vbases;
@ -5955,15 +5965,19 @@ end_of_class (tree t, bool include_virtuals_p, bool include_fields_p = false)
result = offset;
}
if (include_fields_p)
for (tree field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL)
{
offset = size_binop (PLUS_EXPR, DECL_FIELD_OFFSET (field),
DECL_SIZE_UNIT (field));
if (tree_int_cst_lt (result, offset))
result = offset;
}
/* Also consider empty data members. */
for (tree field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL
&& !DECL_ARTIFICIAL (field)
&& field_poverlapping_p (field)
&& is_empty_class (TREE_TYPE (field)))
{
/* Update sizeof(C) to max (sizeof(C), offset(D)+sizeof(D)) */
offset = size_binop (PLUS_EXPR, DECL_FIELD_OFFSET (field),
TYPE_SIZE_UNIT (TREE_TYPE (field)));
if (tree_int_cst_lt (result, offset))
result = offset;
}
if (include_virtuals_p)
for (vbases = CLASSTYPE_VBASECLASSES (t), i = 0;
@ -6154,12 +6168,14 @@ layout_class_type (tree t, tree *virtuals_p)
bool might_overlap = field_poverlapping_p (field);
if (might_overlap && CLASS_TYPE_P (type)
&& CLASSTYPE_NON_LAYOUT_POD_P (type))
&& (CLASSTYPE_NON_LAYOUT_POD_P (type) || CLASSTYPE_EMPTY_P (type)))
{
/* if D is a potentially-overlapping data member, update sizeof(C) to
max (sizeof(C), offset(D)+max (nvsize(D), dsize(D))). */
tree nvsize = CLASSTYPE_SIZE_UNIT (type);
tree dsize = end_of_class (type, /*vbases*/true, /*fields*/true);
/* end_of_class doesn't always give dsize, but it does in the case of
a class with virtual bases, which is when dsize > nvsize. */
tree dsize = end_of_class (type, /*vbases*/true);
if (tree_int_cst_le (dsize, nvsize))
{
DECL_SIZE_UNIT (field) = nvsize;

25
gcc/testsuite/g++.dg/abi/no_unique_address4.C Normal file
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@ -0,0 +1,25 @@
// Test that [[no_unique_address]] makes the enclosing class non-layout-POD.
// { dg-do compile { target c++11 } }
struct A {};
struct B1: A {
int i;
char c;
};
struct B2 {
[[no_unique_address]] A a;
int i;
char c;
};
struct C1: B1 {
char d;
};
struct C2: B2 {
char d;
};
#define SA(X) static_assert((X),#X)
SA(sizeof(C1) == sizeof(C2));

18
gcc/testsuite/g++.dg/abi/no_unique_address5.C Normal file
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@ -0,0 +1,18 @@
// PR c++/88865
// { dg-do compile { target c++11 } }
struct B {};
struct A {
[[no_unique_address]] B a;
[[no_unique_address]] B b;
[[no_unique_address]] B c;
[[no_unique_address]] B d;
};
#define SA(X) static_assert((X),#X)
SA(sizeof(A) == 4);
A a;
SA(&a.a != &a.b);
SA(&a.c != &a.b);
SA(&a.c != &a.d);

12
gcc/testsuite/g++.dg/cpp2a/no_unique_address2.C Normal file
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@ -0,0 +1,12 @@
// PR c++/89089
// { dg-do compile { target c++11 } }
template <typename...> struct A {};
template <typename T, typename... U> struct A<T, U...> {
private:
[[no_unique_address]] A<U...> a;
};
struct B {
template <typename... U> A<U...> operator()(U...) { return A<U...>(); }
} f;
auto fn = f (int{}, [] {});