Implementing this proposal was a pretty straightforward matter of
changing the definition of aggregate and treating artificial base
fields as initializable in aggregate initialization. For this to work
with empty bases, I needed to create base fields for them, which we
haven't done in the past. build_base_field warned about problems with
empty base fields confusing the back end, but I wasn't able to find
any such trouble. For the time being I'm only creating them in C++17
mode, to limit any regressions.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 99ba4ce4ec3daa3897b6bc971381ca4b1cdc54b1
Author: Jason Merrill <ja...@redhat.com>
Date: Fri Oct 14 07:45:02 2016 -0400
Implement P0017R1, C++17 aggregates with bases.
* class.c (build_base_field_1): Split out from...
(build_base_field): ...here. In C++17 mode, build a field for
empty bases.
* decl.c (xref_basetypes): In C++17 aggregates can have bases.
(next_initializable_field): Allow base fields in C++17.
* typeck2.c (process_init_constructor_record): Likewise.
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 46f1bac..9a6ea97 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -4452,6 +4452,34 @@ layout_empty_base (record_layout_info rli, tree binfo,
return atend;
}
+/* Build the FIELD_DECL for BASETYPE as a base of T, add it to the chain of
+ fields at NEXT_FIELD, and return it. */
+
+static tree
+build_base_field_1 (tree t, tree basetype, tree *&next_field)
+{
+ /* Create the FIELD_DECL. */
+ gcc_assert (CLASSTYPE_AS_BASE (basetype));
+ tree decl = build_decl (input_location,
+ FIELD_DECL, NULL_TREE, CLASSTYPE_AS_BASE (basetype));
+ DECL_ARTIFICIAL (decl) = 1;
+ DECL_IGNORED_P (decl) = 1;
+ DECL_FIELD_CONTEXT (decl) = t;
+ DECL_SIZE (decl) = CLASSTYPE_SIZE (basetype);
+ DECL_SIZE_UNIT (decl) = CLASSTYPE_SIZE_UNIT (basetype);
+ SET_DECL_ALIGN (decl, CLASSTYPE_ALIGN (basetype));
+ DECL_USER_ALIGN (decl) = CLASSTYPE_USER_ALIGN (basetype);
+ DECL_MODE (decl) = TYPE_MODE (basetype);
+ DECL_FIELD_IS_BASE (decl) = 1;
+
+ /* Add the new FIELD_DECL to the list of fields for T. */
+ DECL_CHAIN (decl) = *next_field;
+ *next_field = decl;
+ next_field = &DECL_CHAIN (decl);
+
+ return decl;
+}
+
/* Layout the base given by BINFO in the class indicated by RLI.
*BASE_ALIGN is a running maximum of the alignments of
any base class. OFFSETS gives the location of empty base
@@ -4483,29 +4511,12 @@ build_base_field (record_layout_info rli, tree binfo,
CLASSTYPE_EMPTY_P (t) = 0;
/* Create the FIELD_DECL. */
- decl = build_decl (input_location,
- FIELD_DECL, NULL_TREE, CLASSTYPE_AS_BASE (basetype));
- DECL_ARTIFICIAL (decl) = 1;
- DECL_IGNORED_P (decl) = 1;
- DECL_FIELD_CONTEXT (decl) = t;
- if (CLASSTYPE_AS_BASE (basetype))
- {
- DECL_SIZE (decl) = CLASSTYPE_SIZE (basetype);
- DECL_SIZE_UNIT (decl) = CLASSTYPE_SIZE_UNIT (basetype);
- SET_DECL_ALIGN (decl, CLASSTYPE_ALIGN (basetype));
- DECL_USER_ALIGN (decl) = CLASSTYPE_USER_ALIGN (basetype);
- DECL_MODE (decl) = TYPE_MODE (basetype);
- DECL_FIELD_IS_BASE (decl) = 1;
+ decl = build_base_field_1 (t, basetype, next_field);
- /* Try to place the field. It may take more than one try if we
- have a hard time placing the field without putting two
- objects of the same type at the same address. */
- layout_nonempty_base_or_field (rli, decl, binfo, offsets);
- /* Add the new FIELD_DECL to the list of fields for T. */
- DECL_CHAIN (decl) = *next_field;
- *next_field = decl;
- next_field = &DECL_CHAIN (decl);
- }
+ /* Try to place the field. It may take more than one try if we
+ have a hard time placing the field without putting two
+ objects of the same type at the same address. */
+ layout_nonempty_base_or_field (rli, decl, binfo, offsets);
}
else
{
@@ -4541,6 +4552,13 @@ build_base_field (record_layout_info rli, tree binfo,
create CONSTRUCTORs for the class by iterating over the
FIELD_DECLs, and the back end does not handle overlapping
FIELD_DECLs. */
+ if (cxx_dialect >= cxx1z && !BINFO_VIRTUAL_P (binfo))
+ {
+ tree decl = build_base_field_1 (t, basetype, next_field);
+ DECL_FIELD_OFFSET (decl) = BINFO_OFFSET (binfo);
+ DECL_FIELD_BIT_OFFSET (decl) = bitsize_zero_node;
+ SET_DECL_OFFSET_ALIGN (decl, BITS_PER_UNIT);
+ }
/* An empty virtual base causes a class to be non-empty
-- but in that case we do not need to clear CLASSTYPE_EMPTY_P
@@ -6586,7 +6604,7 @@ layout_class_type (tree t, tree *virtuals_p)
/* Make sure that empty classes are reflected in RLI at this
point. */
- include_empty_classes(rli);
+ include_empty_classes (rli);
/* Make sure not to create any structures with zero size. */
if (integer_zerop (rli_size_unit_so_far (rli)) && CLASSTYPE_EMPTY_P (t))
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index f761d0d..d9850e7 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -5569,7 +5569,8 @@ next_initializable_field (tree field)
while (field
&& (TREE_CODE (field) != FIELD_DECL
|| (DECL_C_BIT_FIELD (field) && !DECL_NAME (field))
- || DECL_ARTIFICIAL (field)))
+ || (DECL_ARTIFICIAL (field)
+ && !(cxx_dialect >= cxx1z && DECL_FIELD_IS_BASE (field)))))
field = DECL_CHAIN (field);
return field;
@@ -13150,8 +13151,8 @@ xref_basetypes (tree ref, tree base_list)
if (max_bases)
{
vec_alloc (BINFO_BASE_ACCESSES (binfo), max_bases);
- /* An aggregate cannot have baseclasses. */
- CLASSTYPE_NON_AGGREGATE (ref) = 1;
+ /* A C++98 POD cannot have base classes. */
+ CLASSTYPE_NON_LAYOUT_POD_P (ref) = true;
if (TREE_CODE (ref) == UNION_TYPE)
error ("derived union %qT invalid", ref);
@@ -13179,6 +13180,13 @@ xref_basetypes (tree ref, tree base_list)
if (access == access_default_node)
access = default_access;
+ /* Before C++17, an aggregate cannot have base classes. In C++17, an
+ aggregate can't have virtual, private, or protected base classes. */
+ if (cxx_dialect < cxx1z
+ || access != access_public_node
+ || via_virtual)
+ CLASSTYPE_NON_AGGREGATE (ref) = true;
+
if (PACK_EXPANSION_P (basetype))
basetype = PACK_EXPANSION_PATTERN (basetype);
if (TREE_CODE (basetype) == TYPE_DECL)
diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index 121da32..022a478 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -1352,6 +1352,7 @@ process_init_constructor_record (tree type, tree init,
gcc_assert (TREE_CODE (type) == RECORD_TYPE);
gcc_assert (!CLASSTYPE_VBASECLASSES (type));
gcc_assert (!TYPE_BINFO (type)
+ || cxx_dialect >= cxx1z
|| !BINFO_N_BASE_BINFOS (TYPE_BINFO (type)));
gcc_assert (!TYPE_POLYMORPHIC_P (type));
@@ -1369,7 +1370,9 @@ process_init_constructor_record (tree type, tree init,
if (!DECL_NAME (field) && DECL_C_BIT_FIELD (field))
continue;
- if (TREE_CODE (field) != FIELD_DECL || DECL_ARTIFICIAL (field))
+ if (TREE_CODE (field) != FIELD_DECL
+ || (DECL_ARTIFICIAL (field)
+ && !(cxx_dialect >= cxx1z && DECL_FIELD_IS_BASE (field))))
continue;
/* If this is a bitfield, first convert to the declared type. */
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base1.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base1.C
new file mode 100644
index 0000000..37bb472
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base1.C
@@ -0,0 +1,23 @@
+// { dg-options -std=c++1z }
+// { dg-do run }
+
+struct base1 { int b1, b2 = 42; };
+struct base2 {
+ base2() {
+ b3 = 42;
+ }
+ int b3;
+};
+struct derived : base1, base2 {
+ int d;
+};
+
+derived d1{{1, 2}, {}, 4};
+derived d2{{}, {}, 4};
+
+#define assert(X) do { if (!(X)) __builtin_abort(); } while(0)
+int main()
+{
+ assert (d1.b1 == 1 && d1.b2 == 2 && d1.b3 == 42 && d1.d == 4);
+ assert (d2.b1 == 0 && d2.b2 == 42 && d2.b3 == 42 && d2.d == 4);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base1a.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base1a.C
new file mode 100644
index 0000000..4b28485
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base1a.C
@@ -0,0 +1,15 @@
+// { dg-do compile { target { c++11 && c++14_down } } }
+
+struct base1 { int b1, b2 = 42; };
+struct base2 {
+ base2() {
+ b3 = 42;
+ }
+ int b3;
+};
+struct derived : base1, base2 {
+ int d;
+};
+
+derived d1{{1, 2}, {}, 4}; // { dg-error "" }
+derived d2{{}, {}, 4}; // { dg-error "" }
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base2.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base2.C
new file mode 100644
index 0000000..9da5ebf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base2.C
@@ -0,0 +1,12 @@
+// { dg-options -std=c++1z }
+
+struct derived;
+struct base {
+ friend struct derived;
+private:
+ base();
+};
+struct derived : base {};
+
+derived d1{}; // { dg-error "" "" { target c++1z } }
+derived d2; // still OK
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base2a.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base2a.C
new file mode 100644
index 0000000..821dce1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base2a.C
@@ -0,0 +1,12 @@
+// { dg-do compile { target c++11 } }
+
+struct derived;
+struct base {
+ friend struct derived;
+private:
+ base();
+};
+struct derived : base {};
+
+derived d1{}; // { dg-error "" "" { target c++1z } }
+derived d2; // still OK
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base3.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base3.C
new file mode 100644
index 0000000..4acbc0b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base3.C
@@ -0,0 +1,11 @@
+// { dg-options -std=c++1z }
+
+struct derived;
+struct base { };
+struct derived : base {
+ int i;
+};
+
+derived d1{1}; // { dg-error "base" }
+derived d2{{},1}; // OK
+
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base4.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base4.C
new file mode 100644
index 0000000..fd93f4a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base4.C
@@ -0,0 +1,21 @@
+// { dg-options -std=c++1z }
+// { dg-do run }
+
+struct derived;
+struct base { };
+struct derived : base {
+ int i;
+};
+
+bool flag;
+base f() {
+ flag = true;
+ return base();
+}
+
+derived d2{f(),1};
+
+int main()
+{
+ return (!flag || d2.i != 1);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/aggr-base5.C
b/gcc/testsuite/g++.dg/cpp1z/aggr-base5.C
new file mode 100644
index 0000000..85dd365
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/aggr-base5.C
@@ -0,0 +1,14 @@
+// { dg-options "-std=c++1z -w" }
+// { dg-do run }
+
+struct A { };
+struct B: A { int i; };
+struct C: A, B { int j; };
+
+constexpr C c = { {}, { {}, 1 }, 2 };
+
+#define assert(X) do { if (!(X)) __builtin_abort(); } while(0)
+int main()
+{
+ assert (c.i == 1 && c.j == 2);
+}
