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C++0x constexpr patch #3: implicit constexpr
- From: Jason Merrill <jason at redhat dot com>
- To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 27 Oct 2010 16:10:25 -0400
- Subject: C++0x constexpr patch #3: implicit constexpr
This patch adds support for constexpr on implicitly-declared
constructors; a trivial copy constructor is constexpr, as is a
synthesized default constructor for a class where all the members and
bases have constexpr default constructors.
Tested x86_64-pc-linux-gnu, applied to trunk.
commit 0b1009b4f069adc502a70aa1e0e9f985007b08e9
Author: Jason Merrill <jason@redhat.com>
Date: Wed Oct 27 14:25:09 2010 -0400
* method.c (synthesized_method_walk): Track constexprness too.
(process_subob_fn, walk_field_subobs): Likewise.
(implicitly_declare_fn): Set DECL_DECLARED_CONSTEXPR_P.
(defaulted_late_check): Handle DECL_DECLARED_CONSTEXPR_P.
* class.c (add_implicitly_declared_members): Handle
constexpr default ctor.
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index c3e3c53..a31aad3 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -2672,7 +2672,20 @@ add_implicitly_declared_members (tree t,
if (! TYPE_HAS_USER_CONSTRUCTOR (t))
{
TYPE_HAS_DEFAULT_CONSTRUCTOR (t) = 1;
- CLASSTYPE_LAZY_DEFAULT_CTOR (t) = 1;
+ if (TYPE_HAS_TRIVIAL_DFLT (t))
+ {
+ /* A trivial default constructor is constexpr
+ if there is nothing to initialize. */
+ if (cxx_dialect >= cxx0x && is_really_empty_class (t))
+ TYPE_HAS_CONSTEXPR_CTOR (t) = 1;
+ CLASSTYPE_LAZY_DEFAULT_CTOR (t) = 1;
+ }
+ else if (cxx_dialect >= cxx0x)
+ /* We need to go ahead and declare this to set
+ TYPE_HAS_CONSTEXPR_CTOR. */
+ lazily_declare_fn (sfk_constructor, t);
+ else
+ CLASSTYPE_LAZY_DEFAULT_CTOR (t) = 1;
}
/* [class.ctor]
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 1083e16..6687c75 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -903,7 +903,8 @@ get_copy_assign (tree type)
static void
process_subob_fn (tree fn, bool move_p, tree *spec_p, bool *trivial_p,
- bool *deleted_p, const char *msg, tree arg)
+ bool *deleted_p, bool *constexpr_p,
+ const char *msg, tree arg)
{
if (!fn || fn == error_mark_node)
goto bad;
@@ -935,6 +936,9 @@ process_subob_fn (tree fn, bool move_p, tree *spec_p, bool *trivial_p,
goto bad;
}
+ if (constexpr_p && !DECL_DECLARED_CONSTEXPR_P (fn))
+ *constexpr_p = false;
+
return;
bad:
@@ -949,7 +953,7 @@ static void
walk_field_subobs (tree fields, tree fnname, special_function_kind sfk,
int quals, bool copy_arg_p, bool move_p,
bool assign_p, tree *spec_p, bool *trivial_p,
- bool *deleted_p, const char *msg,
+ bool *deleted_p, bool *constexpr_p, const char *msg,
int flags, tsubst_flags_t complain)
{
tree field;
@@ -1005,6 +1009,13 @@ walk_field_subobs (tree fields, tree fnname, special_function_kind sfk,
if (bad && deleted_p)
*deleted_p = true;
+
+ /* For an implicitly-defined default constructor to be constexpr,
+ every member must have a user-provided default constructor. */
+ /* FIXME will need adjustment for non-static data member
+ initializers. */
+ if (constexpr_p && !CLASS_TYPE_P (mem_type))
+ *constexpr_p = false;
}
if (!CLASS_TYPE_P (mem_type))
@@ -1014,7 +1025,7 @@ walk_field_subobs (tree fields, tree fnname, special_function_kind sfk,
{
walk_field_subobs (TYPE_FIELDS (mem_type), fnname, sfk, quals,
copy_arg_p, move_p, assign_p, spec_p, trivial_p,
- deleted_p, msg, flags, complain);
+ deleted_p, constexpr_p, msg, flags, complain);
continue;
}
@@ -1031,7 +1042,7 @@ walk_field_subobs (tree fields, tree fnname, special_function_kind sfk,
rval = locate_fn_flags (mem_type, fnname, argtype, flags, complain);
process_subob_fn (rval, move_p, spec_p, trivial_p, deleted_p,
- msg, field);
+ constexpr_p, msg, field);
}
}
@@ -1044,7 +1055,7 @@ walk_field_subobs (tree fields, tree fnname, special_function_kind sfk,
static void
synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
tree *spec_p, bool *trivial_p, bool *deleted_p,
- bool diag)
+ bool *constexpr_p, bool diag)
{
tree binfo, base_binfo, scope, fnname, rval, argtype;
bool move_p, copy_arg_p, assign_p, expected_trivial, check_vdtor;
@@ -1078,6 +1089,41 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
*deleted_p = false;
}
+ ctor_p = false;
+ assign_p = false;
+ check_vdtor = false;
+ switch (sfk)
+ {
+ case sfk_move_assignment:
+ case sfk_copy_assignment:
+ assign_p = true;
+ fnname = ansi_assopname (NOP_EXPR);
+ break;
+
+ case sfk_destructor:
+ check_vdtor = true;
+ /* The synthesized method will call base dtors, but check complete
+ here to avoid having to deal with VTT. */
+ fnname = complete_dtor_identifier;
+ break;
+
+ case sfk_constructor:
+ case sfk_move_constructor:
+ case sfk_copy_constructor:
+ ctor_p = true;
+ fnname = complete_ctor_identifier;
+ break;
+
+ default:
+ gcc_unreachable ();
+ }
+
+ /* If that user-written default constructor would satisfy the
+ requirements of a constexpr constructor (7.1.5), the
+ implicitly-defined default constructor is constexpr. */
+ if (constexpr_p)
+ *constexpr_p = ctor_p;
+
move_p = false;
switch (sfk)
{
@@ -1114,35 +1160,6 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
return;
#endif
- ctor_p = false;
- assign_p = false;
- check_vdtor = false;
- switch (sfk)
- {
- case sfk_move_assignment:
- case sfk_copy_assignment:
- assign_p = true;
- fnname = ansi_assopname (NOP_EXPR);
- break;
-
- case sfk_destructor:
- check_vdtor = true;
- /* The synthesized method will call base dtors, but check complete
- here to avoid having to deal with VTT. */
- fnname = complete_dtor_identifier;
- break;
-
- case sfk_constructor:
- case sfk_move_constructor:
- case sfk_copy_constructor:
- ctor_p = true;
- fnname = complete_ctor_identifier;
- break;
-
- default:
- gcc_unreachable ();
- }
-
++cp_unevaluated_operand;
++c_inhibit_evaluation_warnings;
@@ -1183,7 +1200,7 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
rval = locate_fn_flags (base_binfo, fnname, argtype, flags, complain);
process_subob_fn (rval, move_p, spec_p, trivial_p, deleted_p,
- msg, basetype);
+ constexpr_p, msg, basetype);
if (ctor_p && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (basetype))
{
/* In a constructor we also need to check the subobject
@@ -1191,7 +1208,8 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
rval = locate_fn_flags (base_binfo, complete_dtor_identifier,
NULL_TREE, flags, complain);
process_subob_fn (rval, false, &cleanup_spec, &cleanup_trivial,
- &cleanup_deleted, NULL, basetype);
+ &cleanup_deleted, NULL, NULL,
+ basetype);
}
if (check_vdtor && type_has_virtual_destructor (basetype))
@@ -1221,6 +1239,8 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
if (diag)
msg = ("virtual base %qT does not have a move constructor "
"or trivial copy constructor");
+ if (vbases && constexpr_p)
+ *constexpr_p = false;
FOR_EACH_VEC_ELT (tree, vbases, i, base_binfo)
{
tree basetype = BINFO_TYPE (base_binfo);
@@ -1229,13 +1249,14 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
rval = locate_fn_flags (base_binfo, fnname, argtype, flags, complain);
process_subob_fn (rval, move_p, spec_p, trivial_p, deleted_p,
- msg, basetype);
+ constexpr_p, msg, basetype);
if (ctor_p && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (basetype))
{
rval = locate_fn_flags (base_binfo, complete_dtor_identifier,
NULL_TREE, flags, complain);
process_subob_fn (rval, false, &cleanup_spec, &cleanup_trivial,
- &cleanup_deleted, NULL, basetype);
+ &cleanup_deleted, NULL, NULL,
+ basetype);
}
}
}
@@ -1249,12 +1270,13 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p,
"constructor or trivial copy constructor");
walk_field_subobs (TYPE_FIELDS (ctype), fnname, sfk, quals,
copy_arg_p, move_p, assign_p, spec_p, trivial_p,
- deleted_p, msg, flags, complain);
+ deleted_p, constexpr_p, msg, flags, complain);
if (ctor_p)
walk_field_subobs (TYPE_FIELDS (ctype), complete_dtor_identifier,
sfk_destructor, TYPE_UNQUALIFIED, false,
false, false, &cleanup_spec, &cleanup_trivial,
- &cleanup_deleted, NULL, flags, complain);
+ &cleanup_deleted, NULL,
+ NULL, flags, complain);
pop_scope (scope);
@@ -1333,7 +1355,7 @@ maybe_explain_implicit_delete (tree decl)
"definition would be ill-formed:", decl);
pop_scope (scope);
synthesized_method_walk (ctype, sfk, const_p,
- NULL, NULL, NULL, true);
+ NULL, NULL, NULL, NULL, true);
}
input_location = loc;
@@ -1362,6 +1384,7 @@ implicitly_declare_fn (special_function_kind kind, tree type, bool const_p)
HOST_WIDE_INT saved_processing_template_decl;
bool deleted_p;
bool trivial_p;
+ bool constexpr_p;
/* Because we create declarations for implicitly declared functions
lazily, we may be creating the declaration for a member of TYPE
@@ -1431,7 +1454,15 @@ implicitly_declare_fn (special_function_kind kind, tree type, bool const_p)
}
synthesized_method_walk (type, kind, const_p, &raises, &trivial_p,
- &deleted_p, false);
+ &deleted_p, &constexpr_p, false);
+ /* Don't bother marking a deleted constructor as constexpr. */
+ if (deleted_p)
+ constexpr_p = false;
+ /* A trivial copy/move constructor is also a constexpr constructor. */
+ else if (trivial_p && cxx_dialect >= cxx0x
+ && (kind == sfk_copy_constructor
+ || kind == sfk_move_constructor))
+ gcc_assert (constexpr_p);
if (!trivial_p && type_has_trivial_fn (type, kind))
type_set_nontrivial_flag (type, kind);
@@ -1481,7 +1512,10 @@ implicitly_declare_fn (special_function_kind kind, tree type, bool const_p)
DECL_ARTIFICIAL (fn) = 1;
DECL_DEFAULTED_FN (fn) = 1;
if (cxx_dialect >= cxx0x)
- DECL_DELETED_FN (fn) = deleted_p;
+ {
+ DECL_DELETED_FN (fn) = deleted_p;
+ DECL_DECLARED_CONSTEXPR_P (fn) = constexpr_p;
+ }
DECL_NOT_REALLY_EXTERN (fn) = 1;
DECL_DECLARED_INLINE_P (fn) = 1;
gcc_assert (!TREE_USED (fn));
@@ -1521,6 +1555,19 @@ defaulted_late_check (tree fn)
{
tree eh_spec = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (implicit_fn));
TREE_TYPE (fn) = build_exception_variant (TREE_TYPE (fn), eh_spec);
+ if (DECL_DECLARED_CONSTEXPR_P (implicit_fn))
+ /* Hmm...should we do this for out-of-class too? Should it be OK to
+ add constexpr later like inline, rather than requiring
+ declarations to match? */
+ DECL_DECLARED_CONSTEXPR_P (fn) = true;
+ }
+
+ if (!DECL_DECLARED_CONSTEXPR_P (implicit_fn)
+ && DECL_DECLARED_CONSTEXPR_P (fn))
+ {
+ if (!CLASSTYPE_TEMPLATE_INSTANTIATION (ctx))
+ error ("%qD cannot be declared as constexpr", fn);
+ DECL_DECLARED_CONSTEXPR_P (fn) = false;
}
if (DECL_DELETED_FN (implicit_fn))
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-delete.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-delete.C
new file mode 100644
index 0000000..67c9503
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-delete.C
@@ -0,0 +1,3 @@
+// { dg-options -std=c++0x }
+
+constexpr bool never() = delete; // useless, but OK