constexpr functions. These routines are used both during actual parsing
and during the instantiation of template functions.
- Copyright (C) 1998-2019 Free Software Foundation, Inc.
+ Copyright (C) 1998-2020 Free Software Foundation, Inc.
This file is part of GCC.
static bool
cx_check_missing_mem_inits (tree ctype, tree body, bool complain)
{
+ /* We allow uninitialized bases/fields in C++20. */
+ if (cxx_dialect >= cxx2a)
+ return false;
+
unsigned nelts = 0;
if (body)
continue;
if (ANON_AGGR_TYPE_P (TREE_TYPE (field)))
{
- /* Recurse to check the anonummous aggregate member. */
+ /* Recurse to check the anonymous aggregate member. */
bad |= cx_check_missing_mem_inits
(TREE_TYPE (field), NULL_TREE, complain);
if (bad && !complain)
return NULL;
}
- if (!potential_rvalue_constant_expression (massaged))
- {
- if (!DECL_GENERATED_P (fun))
- require_potential_rvalue_constant_expression (massaged);
- return NULL;
- }
+ bool potential = potential_rvalue_constant_expression (massaged);
+ if (!potential && !DECL_GENERATED_P (fun))
+ require_potential_rvalue_constant_expression (massaged);
if (DECL_CONSTRUCTOR_P (fun)
&& cx_check_missing_mem_inits (DECL_CONTEXT (fun),
massaged, !DECL_GENERATED_P (fun)))
+ potential = false;
+
+ if (!potential && !DECL_GENERATED_P (fun))
return NULL;
/* Create the constexpr function table if necessary. */
if (clear_ctx)
DECL_CONTEXT (DECL_RESULT (fun)) = NULL_TREE;
+ if (!potential)
+ /* For a template instantiation, we want to remember the pre-generic body
+ for explain_invalid_constexpr_fn, but do tell cxx_eval_call_expression
+ that it doesn't need to bother trying to expand the function. */
+ entry.result = error_mark_node;
+
gcc_assert (*slot == NULL);
*slot = ggc_alloc<constexpr_fundef> ();
**slot = entry;
{
/* Then if it's OK, the body. */
if (!DECL_DECLARED_CONSTEXPR_P (fun)
- && !LAMBDA_TYPE_P (CP_DECL_CONTEXT (fun)))
+ && DECL_DEFAULTED_FN (fun))
explain_implicit_non_constexpr (fun);
else
{
- body = massage_constexpr_body (fun, DECL_SAVED_TREE (fun));
+ if (constexpr_fundef *fd = retrieve_constexpr_fundef (fun))
+ body = fd->body;
+ else
+ body = DECL_SAVED_TREE (fun);
+ body = massage_constexpr_body (fun, body);
require_potential_rvalue_constant_expression (body);
if (DECL_CONSTRUCTOR_P (fun))
cx_check_missing_mem_inits (DECL_CONTEXT (fun), body, true);
return boolean_true_node;
}
+ if (fndecl_built_in_p (fun, CP_BUILT_IN_SOURCE_LOCATION, BUILT_IN_FRONTEND))
+ return fold_builtin_source_location (EXPR_LOCATION (t));
+
/* Be permissive for arguments to built-ins; __builtin_constant_p should
return constant false for a non-constant argument. */
constexpr_ctx new_ctx = *ctx;
if (!*non_constant_p)
{
- /* Unsharing here isn't necessary for correctness, but it
- significantly improves memory performance for some reason. */
- arg = unshare_constructor (arg);
/* Make sure the binding has the same type as the parm. But
only for constant args. */
if (!TYPE_REF_P (type))
return decl_in_std_namespace_p (decl);
}
+/* Return true if FNDECL is __dynamic_cast. */
+
+static inline bool
+cxx_dynamic_cast_fn_p (tree fndecl)
+{
+ return (cxx_dialect >= cxx2a
+ && id_equal (DECL_NAME (fndecl), "__dynamic_cast")
+ && CP_DECL_CONTEXT (fndecl) == global_namespace);
+}
+
+/* Often, we have an expression in the form of address + offset, e.g.
+ "&_ZTV1A + 16". Extract the object from it, i.e. "_ZTV1A". */
+
+static tree
+extract_obj_from_addr_offset (tree expr)
+{
+ if (TREE_CODE (expr) == POINTER_PLUS_EXPR)
+ expr = TREE_OPERAND (expr, 0);
+ STRIP_NOPS (expr);
+ if (TREE_CODE (expr) == ADDR_EXPR)
+ expr = TREE_OPERAND (expr, 0);
+ return expr;
+}
+
+/* Given a PATH like
+
+ g.D.2181.D.2154.D.2102.D.2093
+
+ find a component with type TYPE. Return NULL_TREE if not found, and
+ error_mark_node if the component is not accessible. If STOP is non-null,
+ this function will return NULL_TREE if STOP is found before TYPE. */
+
+static tree
+get_component_with_type (tree path, tree type, tree stop)
+{
+ while (true)
+ {
+ if (same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (path), type))
+ /* Found it. */
+ return path;
+ else if (stop
+ && (same_type_ignoring_top_level_qualifiers_p (TREE_TYPE (path),
+ stop)))
+ return NULL_TREE;
+ else if (TREE_CODE (path) == COMPONENT_REF
+ && DECL_FIELD_IS_BASE (TREE_OPERAND (path, 1)))
+ {
+ /* We need to check that the component we're accessing is in fact
+ accessible. */
+ if (TREE_PRIVATE (TREE_OPERAND (path, 1))
+ || TREE_PROTECTED (TREE_OPERAND (path, 1)))
+ return error_mark_node;
+ path = TREE_OPERAND (path, 0);
+ }
+ else
+ return NULL_TREE;
+ }
+}
+
+/* Evaluate a call to __dynamic_cast (permitted by P1327R1).
+
+ The declaration of __dynamic_cast is:
+
+ void* __dynamic_cast (const void* __src_ptr,
+ const __class_type_info* __src_type,
+ const __class_type_info* __dst_type,
+ ptrdiff_t __src2dst);
+
+ where src2dst has the following possible values
+
+ >-1: src_type is a unique public non-virtual base of dst_type
+ dst_ptr + src2dst == src_ptr
+ -1: unspecified relationship
+ -2: src_type is not a public base of dst_type
+ -3: src_type is a multiple public non-virtual base of dst_type
+
+ Since literal types can't have virtual bases, we only expect hint >=0,
+ -2, or -3. */
+
+static tree
+cxx_eval_dynamic_cast_fn (const constexpr_ctx *ctx, tree call,
+ bool *non_constant_p, bool *overflow_p)
+{
+ /* T will be something like
+ __dynamic_cast ((B*) b, &_ZTI1B, &_ZTI1D, 8)
+ dismantle it. */
+ gcc_assert (call_expr_nargs (call) == 4);
+ tsubst_flags_t complain = ctx->quiet ? tf_none : tf_warning_or_error;
+ tree obj = CALL_EXPR_ARG (call, 0);
+ tree type = CALL_EXPR_ARG (call, 2);
+ HOST_WIDE_INT hint = int_cst_value (CALL_EXPR_ARG (call, 3));
+ location_t loc = cp_expr_loc_or_input_loc (call);
+
+ /* Get the target type of the dynamic_cast. */
+ gcc_assert (TREE_CODE (type) == ADDR_EXPR);
+ type = TREE_OPERAND (type, 0);
+ type = TREE_TYPE (DECL_NAME (type));
+
+ /* TYPE can only be either T* or T&. We can't know which of these it
+ is by looking at TYPE, but OBJ will be "(T*) x" in the first case,
+ and something like "(T*)(T&)(T*) x" in the second case. */
+ bool reference_p = false;
+ while (CONVERT_EXPR_P (obj) || TREE_CODE (obj) == SAVE_EXPR)
+ {
+ reference_p |= TYPE_REF_P (TREE_TYPE (obj));
+ obj = TREE_OPERAND (obj, 0);
+ }
+
+ /* Evaluate the object so that we know its dynamic type. */
+ obj = cxx_eval_constant_expression (ctx, obj, /*lval*/false, non_constant_p,
+ overflow_p);
+ if (*non_constant_p)
+ return call;
+
+ /* We expect OBJ to be in form of &d.D.2102 when HINT == 0,
+ but when HINT is > 0, it can also be something like
+ &d.D.2102 + 18446744073709551608, which includes the BINFO_OFFSET. */
+ obj = extract_obj_from_addr_offset (obj);
+ const tree objtype = TREE_TYPE (obj);
+ /* If OBJ doesn't refer to a base field, we're done. */
+ if (tree t = (TREE_CODE (obj) == COMPONENT_REF
+ ? TREE_OPERAND (obj, 1) : obj))
+ if (TREE_CODE (t) != FIELD_DECL || !DECL_FIELD_IS_BASE (t))
+ return integer_zero_node;
+
+ /* [class.cdtor] When a dynamic_cast is used in a constructor ...
+ or in a destructor ... if the operand of the dynamic_cast refers
+ to the object under construction or destruction, this object is
+ considered to be a most derived object that has the type of the
+ constructor or destructor's class. */
+ tree vtable = build_vfield_ref (obj, TREE_TYPE (obj));
+ vtable = cxx_eval_constant_expression (ctx, vtable, /*lval*/false,
+ non_constant_p, overflow_p);
+ if (*non_constant_p)
+ return call;
+ /* VTABLE will be &_ZTV1A + 16 or similar, get _ZTV1A. */
+ vtable = extract_obj_from_addr_offset (vtable);
+ const tree mdtype = DECL_CONTEXT (vtable);
+
+ /* Given dynamic_cast<T>(v),
+
+ [expr.dynamic.cast] If C is the class type to which T points or refers,
+ the runtime check logically executes as follows:
+
+ If, in the most derived object pointed (referred) to by v, v points
+ (refers) to a public base class subobject of a C object, and if only
+ one object of type C is derived from the subobject pointed (referred)
+ to by v the result points (refers) to that C object.
+
+ In this case, HINT >= 0 or -3. */
+ if (hint >= 0 || hint == -3)
+ {
+ /* Look for a component with type TYPE. */
+ tree t = get_component_with_type (obj, type, mdtype);
+ /* If not accessible, give an error. */
+ if (t == error_mark_node)
+ {
+ if (reference_p)
+ {
+ if (!ctx->quiet)
+ {
+ error_at (loc, "reference %<dynamic_cast%> failed");
+ inform (loc, "static type %qT of its operand is a "
+ "non-public base class of dynamic type %qT",
+ objtype, type);
+
+ }
+ *non_constant_p = true;
+ }
+ return integer_zero_node;
+ }
+ else if (t)
+ /* The result points to the TYPE object. */
+ return cp_build_addr_expr (t, complain);
+ /* Else, TYPE was not found, because the HINT turned out to be wrong.
+ Fall through to the normal processing. */
+ }
+
+ /* Otherwise, if v points (refers) to a public base class subobject of the
+ most derived object, and the type of the most derived object has a base
+ class, of type C, that is unambiguous and public, the result points
+ (refers) to the C subobject of the most derived object.
+
+ But it can also be an invalid case. */
+
+ /* Get the most derived object. */
+ obj = get_component_with_type (obj, mdtype, NULL_TREE);
+ if (obj == error_mark_node)
+ {
+ if (reference_p)
+ {
+ if (!ctx->quiet)
+ {
+ error_at (loc, "reference %<dynamic_cast%> failed");
+ inform (loc, "static type %qT of its operand is a non-public"
+ " base class of dynamic type %qT", objtype, mdtype);
+ }
+ *non_constant_p = true;
+ }
+ return integer_zero_node;
+ }
+ else
+ gcc_assert (obj);
+
+ /* Check that the type of the most derived object has a base class
+ of type TYPE that is unambiguous and public. */
+ base_kind b_kind;
+ tree binfo = lookup_base (mdtype, type, ba_check, &b_kind, tf_none);
+ if (!binfo || binfo == error_mark_node)
+ {
+ if (reference_p)
+ {
+ if (!ctx->quiet)
+ {
+ error_at (loc, "reference %<dynamic_cast%> failed");
+ if (b_kind == bk_ambig)
+ inform (loc, "%qT is an ambiguous base class of dynamic "
+ "type %qT of its operand", type, mdtype);
+ else
+ inform (loc, "dynamic type %qT of its operand does not "
+ "have an unambiguous public base class %qT",
+ mdtype, type);
+ }
+ *non_constant_p = true;
+ }
+ return integer_zero_node;
+ }
+ /* If so, return the TYPE subobject of the most derived object. */
+ obj = convert_to_base_statically (obj, binfo);
+ return cp_build_addr_expr (obj, complain);
+}
+
/* Subroutine of cxx_eval_constant_expression.
Evaluate the call expression tree T in the context of OLD_CALL expression
evaluation. */
gcc_assert (arg1);
return arg1;
}
+ else if (cxx_dynamic_cast_fn_p (fun))
+ return cxx_eval_dynamic_cast_fn (ctx, t, non_constant_p, overflow_p);
+
if (!ctx->quiet)
{
if (!lambda_static_thunk_p (fun))
{
new_call.fundef = retrieve_constexpr_fundef (fun);
if (new_call.fundef == NULL || new_call.fundef->body == NULL
+ || new_call.fundef->result == error_mark_node
|| fun == current_function_decl)
{
if (!ctx->quiet)
this function exits. */
class free_bindings
{
+ tree *bindings;
public:
- tree &bindings;
- bool do_free;
- free_bindings (tree &b): bindings (b), do_free(true) { }
- void preserve () { do_free = false; }
- ~free_bindings () {
- if (do_free)
- {
- for (int i = 0; i < TREE_VEC_LENGTH (bindings); ++i)
- free_constructor (TREE_VEC_ELT (bindings, i));
- ggc_free (bindings);
- }
- }
+ free_bindings (tree &b): bindings (&b) { }
+ ~free_bindings () { if (bindings) ggc_free (*bindings); }
+ void preserve () { bindings = NULL; }
} fb (new_call.bindings);
if (*non_constant_p)
for (int i = 0; i < TREE_VEC_LENGTH (bound); ++i)
{
tree arg = TREE_VEC_ELT (bound, i);
- /* Don't share a CONSTRUCTOR that might be changed. */
+ if (entry)
+ {
+ /* Unshare args going into the hash table to separate them
+ from the caller's context, for better GC and to avoid
+ problems with verify_gimple. */
+ arg = unshare_expr_without_location (arg);
+ TREE_VEC_ELT (bound, i) = arg;
+ }
+ /* Don't share a CONSTRUCTOR that might be changed. This is not
+ redundant with the unshare just above; we also don't want to
+ change the argument values in the hash table. XXX Could we
+ unshare lazily in cxx_eval_store_expression? */
arg = unshare_constructor (arg);
if (TREE_CODE (arg) == CONSTRUCTOR)
vec_safe_push (ctors, arg);
entry->result = result;
}
- /* The result of a constexpr function must be completely initialized. */
- if (TREE_CODE (result) == CONSTRUCTOR)
+ /* The result of a constexpr function must be completely initialized.
+
+ However, in C++20, a constexpr constructor doesn't necessarily have
+ to initialize all the fields, so we don't clear CONSTRUCTOR_NO_CLEARING
+ in order to detect reading an unitialized object in constexpr instead
+ of value-initializing it. (reduced_constant_expression_p is expected to
+ take care of clearing the flag.) */
+ if (TREE_CODE (result) == CONSTRUCTOR
+ && (cxx_dialect < cxx2a
+ || !DECL_CONSTRUCTOR_P (fun)))
clear_no_implicit_zero (result);
pop_cx_call_context ();
return result;
}
-/* FIXME speed this up, it's taking 16% of compile time on sieve testcase. */
+/* Return true if T is a valid constant initializer. If a CONSTRUCTOR
+ initializes all the members, the CONSTRUCTOR_NO_CLEARING flag will be
+ cleared.
+ FIXME speed this up, it's taking 16% of compile time on sieve testcase. */
bool
reduced_constant_expression_p (tree t)
if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE)
/* An initialized vector would have a VECTOR_CST. */
return false;
+ else if (cxx_dialect >= cxx2a
+ /* An ARRAY_TYPE doesn't have any TYPE_FIELDS. */
+ && (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE
+ /* A union only initializes one member. */
+ || TREE_CODE (TREE_TYPE (t)) == UNION_TYPE))
+ field = NULL_TREE;
else
field = next_initializable_field (TYPE_FIELDS (TREE_TYPE (t)));
}
return false;
if (field)
{
- if (idx != field)
- return false;
+ /* Empty class field may or may not have an initializer. */
+ for (; idx != field;
+ field = next_initializable_field (DECL_CHAIN (field)))
+ if (!is_really_empty_class (TREE_TYPE (field),
+ /*ignore_vptr*/false))
+ return false;
field = next_initializable_field (DECL_CHAIN (field));
}
}
- if (field)
- return false;
- else if (CONSTRUCTOR_NO_CLEARING (t))
+ /* There could be a non-empty field at the end. */
+ for (; field; field = next_initializable_field (DECL_CHAIN (field)))
+ if (!is_really_empty_class (TREE_TYPE (field), /*ignore_vptr*/false))
+ return false;
+ if (CONSTRUCTOR_NO_CLEARING (t))
/* All the fields are initialized. */
CONSTRUCTOR_NO_CLEARING (t) = false;
return true;
&& (!cxx_placement_new_fn (fun)
|| TREE_CODE (t) != CALL_EXPR
|| current_function_decl == NULL_TREE
- || !is_std_construct_at (current_function_decl)))
+ || !is_std_construct_at (current_function_decl))
+ && !cxx_dynamic_cast_fn_p (fun))
{
if (flags & tf_error)
{