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Code Issues Releases Activity

Fix conflicts.

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This commit is contained in:
David E. O'Brien 2000-05-27 02:43:50 +00:00
parent 1318f6d724
commit 507f261243
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=60970
4 changed files with 669 additions and 258 deletions
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617
contrib/gcc/cp/decl.c
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@ -190,6 +190,8 @@ static tree record_builtin_java_type PROTO((const char *, int));
static const char *tag_name PROTO((enum tag_types code));
static void find_class_binding_level PROTO((void));
static struct binding_level *innermost_nonclass_level PROTO((void));
static void finish_dtor PROTO((void));
static void finish_ctor PROTO((int));
static tree poplevel_class PROTO((void));
static void warn_about_implicit_typename_lookup PROTO((tree, tree));
static int walk_namespaces_r PROTO((tree, walk_namespaces_fn, void *));
@ -337,6 +339,15 @@ tree __ptr_desc_array_type, __attr_dec_array_type, __func_desc_array_type;
tree __ptmf_desc_array_type, __ptmd_desc_array_type;
#endif
/* This is the identifier __vlist. */
tree vlist_identifier;
/* This is the type _Vlist = vtable_entry_type**. */
tree vlist_type_node;
/* A null pointer of type _Vlist. */
tree vlist_zero_node;
/* Indicates that there is a type value in some namespace, although
that is not necessarily in scope at the moment. */
@ -6285,6 +6296,7 @@ init_decl_processing ()
this_identifier = get_identifier (THIS_NAME);
in_charge_identifier = get_identifier (IN_CHARGE_NAME);
vlist_identifier = get_identifier (VLIST_NAME);
ctor_identifier = get_identifier (CTOR_NAME);
dtor_identifier = get_identifier (DTOR_NAME);
pfn_identifier = get_identifier (VTABLE_PFN_NAME);
@ -6512,6 +6524,7 @@ init_decl_processing ()
#if 0
record_builtin_type (RID_MAX, NULL_PTR, ptr_type_node);
#endif
endlink = void_list_node;
int_endlink = tree_cons (NULL_TREE, integer_type_node, endlink);
double_endlink = tree_cons (NULL_TREE, double_type_node, endlink);
@ -6851,6 +6864,16 @@ init_decl_processing ()
layout_type (vtbl_ptr_type_node);
record_builtin_type (RID_MAX, NULL_PTR, vtbl_ptr_type_node);
if (flag_vtable_thunks)
{
/* We need vlists only when using thunks; otherwise leave them
as NULL_TREE. That way, it doesn't get into the way of the
mangling. */
vlist_type_node = build_pointer_type (vtbl_ptr_type_node);
vlist_zero_node = build_int_2 (0, 0);
TREE_TYPE (vlist_zero_node) = vlist_type_node;
}
/* Simplify life by making a "sigtable_entry_type". Give its
fields names so that the debugger can use them. */
@ -11388,6 +11411,10 @@ grokdeclarator (declarator, declspecs, decl_context, initialized, attrlist)
if (TYPE_USES_VIRTUAL_BASECLASSES (DECL_CONTEXT (decl)))
arg_types = TREE_CHAIN (arg_types);
/* And the `vlist' argument. */
if (TYPE_USES_PVBASES (DECL_CONTEXT (decl)))
arg_types = TREE_CHAIN (arg_types);
if (arg_types == void_list_node
|| (arg_types
&& TREE_CHAIN (arg_types)
@ -12082,6 +12109,9 @@ replace_defarg (arg, init)
TREE_PURPOSE (arg) = init;
}
/* Return 1 if D copies its arguments. This is used to test for copy
constructors and copy assignment operators. */
int
copy_args_p (d)
tree d;
@ -12089,7 +12119,12 @@ copy_args_p (d)
tree t = FUNCTION_ARG_CHAIN (d);
if (DECL_CONSTRUCTOR_P (d)
&& TYPE_USES_VIRTUAL_BASECLASSES (DECL_CONTEXT (d)))
t = TREE_CHAIN (t);
{
t = TREE_CHAIN (t);
if (TYPE_USES_PVBASES (DECL_CONTEXT (d)))
t = TREE_CHAIN (t);
}
if (t && TREE_CODE (TREE_VALUE (t)) == REFERENCE_TYPE
&& (TYPE_MAIN_VARIANT (TREE_TYPE (TREE_VALUE (t)))
== DECL_CLASS_CONTEXT (d))
@ -12119,7 +12154,8 @@ grok_ctor_properties (ctype, decl)
added to any ctor so we can tell if the class has been initialized
yet. This could screw things up in this function, so we deliberately
ignore the leading int if we're in that situation. */
if (TYPE_USES_VIRTUAL_BASECLASSES (ctype))
if (TYPE_USES_VIRTUAL_BASECLASSES (ctype)
&& !CLASSTYPE_IS_TEMPLATE (ctype))
{
my_friendly_assert (parmtypes
&& TREE_VALUE (parmtypes) == integer_type_node,
@ -12128,6 +12164,15 @@ grok_ctor_properties (ctype, decl)
parmtype = TREE_VALUE (parmtypes);
}
if (TYPE_USES_PVBASES (ctype))
{
my_friendly_assert (parmtypes
&& TREE_VALUE (parmtypes) == vlist_type_node,
980529);
parmtypes = TREE_CHAIN (parmtypes);
parmtype = TREE_VALUE (parmtypes);
}
/* [class.copy]
A non-template constructor for class X is a copy constructor if
@ -12925,6 +12970,16 @@ xref_basetypes (code_type_node, name, ref, binfo)
{
TYPE_USES_VIRTUAL_BASECLASSES (ref) = 1;
TYPE_USES_COMPLEX_INHERITANCE (ref) = 1;
/* The PVBASES flag is never set for templates; we know
only for instantiations whether the virtual bases are
polymorphic. */
if (flag_vtable_thunks >= 2 && !CLASSTYPE_IS_TEMPLATE (ref))
{
if (via_virtual && TYPE_VIRTUAL_P (basetype))
TYPE_USES_PVBASES (ref) = 1;
else if (TYPE_USES_PVBASES (basetype))
TYPE_USES_PVBASES (ref) = 1;
}
}
if (CLASS_TYPE_P (basetype))
@ -13930,6 +13985,313 @@ store_return_init (return_id, init)
}
/* Emit implicit code for a destructor. This is a subroutine of
finish_function. */
static void
finish_dtor ()
{
tree binfo = TYPE_BINFO (current_class_type);
tree cond = integer_one_node;
tree exprstmt;
tree in_charge_node = lookup_name (in_charge_identifier, 0);
tree virtual_size;
int ok_to_optimize_dtor = 0;
int empty_dtor = get_last_insn () == last_dtor_insn;
rtx insns, last_parm_insn;
if (current_function_assigns_this)
cond = build (NE_EXPR, boolean_type_node,
current_class_ptr, integer_zero_node);
else
{
int n_baseclasses = CLASSTYPE_N_BASECLASSES (current_class_type);
/* If this destructor is empty, then we don't need to check
whether `this' is NULL in some cases. */
if ((flag_this_is_variable & 1) == 0)
ok_to_optimize_dtor = 1;
else if (empty_dtor)
ok_to_optimize_dtor
= (n_baseclasses == 0
|| (n_baseclasses == 1
&& TYPE_HAS_DESTRUCTOR (TYPE_BINFO_BASETYPE (current_class_type, 0))));
}
/* If this has a vlist1 parameter, allocate the corresponding vlist
parameter. */
if (DECL_DESTRUCTOR_FOR_PVBASE_P (current_function_decl))
{
/* _Vlist __vlist; */
tree vlist;
mark_all_temps_used();
vlist = pushdecl (build_decl (VAR_DECL, vlist_identifier,
vlist_type_node));
TREE_USED (vlist) = 1;
DECL_ARTIFICIAL (vlist) = 1;
expand_decl (vlist);
expand_decl_init (vlist);
}
/* These initializations might go inline. Protect
the binding level of the parms. */
pushlevel (0);
expand_start_bindings (0);
if (current_function_assigns_this)
{
current_function_assigns_this = 0;
current_function_just_assigned_this = 0;
}
/* Generate the code to call destructor on base class.
If this destructor belongs to a class with virtual
functions, then set the virtual function table
pointer to represent the type of our base class. */
/* This side-effect makes call to `build_delete' generate the
code we have to have at the end of this destructor.
`build_delete' will set the flag again. */
TYPE_HAS_DESTRUCTOR (current_class_type) = 0;
/* These are two cases where we cannot delegate deletion. */
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type)
|| TYPE_GETS_REG_DELETE (current_class_type))
exprstmt = build_delete
(current_class_type, current_class_ref, integer_zero_node,
LOOKUP_NONVIRTUAL|LOOKUP_DESTRUCTOR|LOOKUP_NORMAL, 0);
else
exprstmt = build_delete
(current_class_type, current_class_ref, in_charge_node,
LOOKUP_NONVIRTUAL|LOOKUP_DESTRUCTOR|LOOKUP_NORMAL, 0);
/* If we did not assign to this, then `this' is non-zero at
the end of a destructor. As a special optimization, don't
emit test if this is an empty destructor. If it does nothing,
it does nothing. If it calls a base destructor, the base
destructor will perform the test. */
if (exprstmt != error_mark_node
&& (TREE_CODE (exprstmt) != NOP_EXPR
|| TREE_OPERAND (exprstmt, 0) != integer_zero_node
|| TYPE_USES_VIRTUAL_BASECLASSES (current_class_type)))
{
expand_label (dtor_label);
if (cond != integer_one_node)
expand_start_cond (cond, 0);
if (exprstmt != void_zero_node)
/* Don't call `expand_expr_stmt' if we're not going to do
anything, since -Wall will give a diagnostic. */
expand_expr_stmt (exprstmt);
/* Run destructor on all virtual baseclasses. */
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
{
tree vbases = nreverse
(copy_list (CLASSTYPE_VBASECLASSES (current_class_type)));
expand_start_cond (build (BIT_AND_EXPR, integer_type_node,
in_charge_node, integer_two_node), 0);
while (vbases)
{
if (TYPE_NEEDS_DESTRUCTOR (BINFO_TYPE (vbases)))
{
tree vb = get_vbase
(BINFO_TYPE (vbases),
TYPE_BINFO (current_class_type));
expand_expr_stmt
(build_base_dtor_call (current_class_ref,
vb, integer_zero_node));
}
vbases = TREE_CHAIN (vbases);
}
expand_end_cond ();
}
do_pending_stack_adjust ();
if (cond != integer_one_node)
expand_end_cond ();
}
virtual_size = c_sizeof (current_class_type);
/* At the end, call delete if that's what's requested. */
/* FDIS sez: At the point of definition of a virtual destructor
(including an implicit definition), non-placement operator
delete shall be looked up in the scope of the destructor's
class and if found shall be accessible and unambiguous.
This is somewhat unclear, but I take it to mean that if the
class only defines placement deletes we don't do anything here.
So we pass LOOKUP_SPECULATIVELY; delete_sanity will complain
for us if they ever try to delete one of these. */
if (TYPE_GETS_REG_DELETE (current_class_type)
|| TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
exprstmt = build_op_delete_call
(DELETE_EXPR, current_class_ptr, virtual_size,
LOOKUP_NORMAL | LOOKUP_SPECULATIVELY, NULL_TREE);
else
exprstmt = NULL_TREE;
if (exprstmt)
{
cond = build (BIT_AND_EXPR, integer_type_node,
in_charge_node, integer_one_node);
expand_start_cond (cond, 0);
expand_expr_stmt (exprstmt);
expand_end_cond ();
}
/* End of destructor. */
expand_end_bindings (NULL_TREE, getdecls () != NULL_TREE, 0);
poplevel (getdecls () != NULL_TREE, 0, 0);
/* Back to the top of destructor. */
/* Don't execute destructor code if `this' is NULL. */
start_sequence ();
/* If we need thunk-style vlists, initialize them if the caller did
not pass them. This requires a new temporary. The generated code
looks like
if (!(__in_charge & 4))
__vlist = __vl.<type> + sizeof(__vl.<type>);
else
__vlist = __vlist1;
*/
if (TYPE_USES_PVBASES (current_class_type))
{
tree vlist = lookup_name (vlist_identifier, 0);
tree vlist1 = lookup_name (get_identifier (VLIST1_NAME), 0);
cond = build (BIT_AND_EXPR, integer_type_node,
in_charge_node, build_int_2 (4, 0));
cond = build1 (TRUTH_NOT_EXPR, boolean_type_node, cond);
expand_start_cond (cond, 0);
init_vlist (current_class_type);
expand_start_else ();
expand_expr_stmt (build_modify_expr (vlist, NOP_EXPR, vlist1));
expand_end_cond ();
}
/* If the dtor is empty, and we know there is not possible way we
could use any vtable entries, before they are possibly set by
a base class dtor, we don't have to setup the vtables, as we
know that any base class dtoring will set up any vtables it
needs. We avoid MI, because one base class dtor can do a
virtual dispatch to an overridden function that would need to
have a non-related vtable set up, we cannot avoid setting up
vtables in that case. We could change this to see if there is
just one vtable. */
if (! empty_dtor || TYPE_USES_COMPLEX_INHERITANCE (current_class_type))
{
/* Make all virtual function table pointers in non-virtual base
classes point to CURRENT_CLASS_TYPE's virtual function
tables. */
expand_direct_vtbls_init (binfo, binfo, 1, 0, current_class_ptr);
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
expand_indirect_vtbls_init (binfo, current_class_ref, current_class_ptr);
}
if (! ok_to_optimize_dtor)
{
cond = build_binary_op (NE_EXPR,
current_class_ptr, integer_zero_node);
expand_start_cond (cond, 0);
}
insns = get_insns ();
end_sequence ();
last_parm_insn = get_first_nonparm_insn ();
if (last_parm_insn == NULL_RTX)
last_parm_insn = get_last_insn ();
else
last_parm_insn = previous_insn (last_parm_insn);
emit_insns_after (insns, last_parm_insn);
if (! ok_to_optimize_dtor)
expand_end_cond ();
}
/* Emit implicit code for a constructor. This is a subroutine of
finish_function. CALL_POPLEVEL is the same variable in
finish_function. */
static void
finish_ctor (call_poplevel)
int call_poplevel;
{
register tree fndecl = current_function_decl;
tree cond = NULL_TREE, thenclause = NULL_TREE;
rtx insns;
tree decls;
/* Allow constructor for a type to get a new instance of the object
using `build_new'. */
tree abstract_virtuals = CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type);
CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type) = NULL_TREE;
if (flag_this_is_variable > 0)
{
cond = build_binary_op (EQ_EXPR, current_class_ptr, integer_zero_node);
thenclause =
build_modify_expr (current_class_ptr, NOP_EXPR,
build_new (NULL_TREE, current_class_type,
void_type_node, 0));
}
CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type) = abstract_virtuals;
start_sequence ();
if (flag_this_is_variable > 0)
{
expand_start_cond (cond, 0);
expand_expr_stmt (thenclause);
expand_end_cond ();
}
/* Emit insns from `emit_base_init' which sets up virtual
function table pointer(s). */
if (base_init_expr)
{
expand_expr_stmt (base_init_expr);
base_init_expr = NULL_TREE;
}
insns = get_insns ();
end_sequence ();
/* This is where the body of the constructor begins. */
emit_insns_after (insns, last_parm_cleanup_insn);
end_protect_partials ();
/* This is where the body of the constructor ends. */
expand_label (ctor_label);
ctor_label = NULL_TREE;
if (call_poplevel)
{
decls = getdecls ();
expand_end_bindings (decls, decls != NULL_TREE, 0);
poplevel (decls != NULL_TREE, 1, 0);
}
/* c_expand_return knows to return 'this' from a constructor. */
c_expand_return (NULL_TREE);
current_function_assigns_this = 0;
current_function_just_assigned_this = 0;
}
/* Finish up a function declaration and compile that function
all the way to assembler language output. The free the storage
for the function definition.
@ -13958,7 +14320,6 @@ finish_function (lineno, flags, nested)
{
register tree fndecl = current_function_decl;
tree fntype, ctype = NULL_TREE;
rtx last_parm_insn, insns;
/* Label to use if this function is supposed to return a value. */
tree no_return_label = NULL_TREE;
tree decls = NULL_TREE;
@ -14020,191 +14381,7 @@ finish_function (lineno, flags, nested)
do_pending_stack_adjust ();
if (dtor_label)
{
tree binfo = TYPE_BINFO (current_class_type);
tree cond = integer_one_node;
tree exprstmt;
tree in_charge_node = lookup_name (in_charge_identifier, 0);
tree virtual_size;
int ok_to_optimize_dtor = 0;
int empty_dtor = get_last_insn () == last_dtor_insn;
if (current_function_assigns_this)
cond = build (NE_EXPR, boolean_type_node,
current_class_ptr, integer_zero_node);
else
{
int n_baseclasses = CLASSTYPE_N_BASECLASSES (current_class_type);
/* If this destructor is empty, then we don't need to check
whether `this' is NULL in some cases. */
if ((flag_this_is_variable & 1) == 0)
ok_to_optimize_dtor = 1;
else if (empty_dtor)
ok_to_optimize_dtor
= (n_baseclasses == 0
|| (n_baseclasses == 1
&& TYPE_HAS_DESTRUCTOR (TYPE_BINFO_BASETYPE (current_class_type, 0))));
}
/* These initializations might go inline. Protect
the binding level of the parms. */
pushlevel (0);
expand_start_bindings (0);
if (current_function_assigns_this)
{
current_function_assigns_this = 0;
current_function_just_assigned_this = 0;
}
/* Generate the code to call destructor on base class.
If this destructor belongs to a class with virtual
functions, then set the virtual function table
pointer to represent the type of our base class. */
/* This side-effect makes call to `build_delete' generate the
code we have to have at the end of this destructor.
`build_delete' will set the flag again. */
TYPE_HAS_DESTRUCTOR (current_class_type) = 0;
/* These are two cases where we cannot delegate deletion. */
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type)
|| TYPE_GETS_REG_DELETE (current_class_type))
exprstmt = build_delete (current_class_type, current_class_ref, integer_zero_node,
LOOKUP_NONVIRTUAL|LOOKUP_DESTRUCTOR|LOOKUP_NORMAL, 0);
else
exprstmt = build_delete (current_class_type, current_class_ref, in_charge_node,
LOOKUP_NONVIRTUAL|LOOKUP_DESTRUCTOR|LOOKUP_NORMAL, 0);
/* If we did not assign to this, then `this' is non-zero at
the end of a destructor. As a special optimization, don't
emit test if this is an empty destructor. If it does nothing,
it does nothing. If it calls a base destructor, the base
destructor will perform the test. */
if (exprstmt != error_mark_node
&& (TREE_CODE (exprstmt) != NOP_EXPR
|| TREE_OPERAND (exprstmt, 0) != integer_zero_node
|| TYPE_USES_VIRTUAL_BASECLASSES (current_class_type)))
{
expand_label (dtor_label);
if (cond != integer_one_node)
expand_start_cond (cond, 0);
if (exprstmt != void_zero_node)
/* Don't call `expand_expr_stmt' if we're not going to do
anything, since -Wall will give a diagnostic. */
expand_expr_stmt (exprstmt);
/* Run destructor on all virtual baseclasses. */
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
{
tree vbases = nreverse (copy_list (CLASSTYPE_VBASECLASSES (current_class_type)));
expand_start_cond (build (BIT_AND_EXPR, integer_type_node,
in_charge_node, integer_two_node), 0);
while (vbases)
{
if (TYPE_NEEDS_DESTRUCTOR (BINFO_TYPE (vbases)))
{
tree vb = get_vbase
(BINFO_TYPE (vbases),
TYPE_BINFO (current_class_type));
expand_expr_stmt
(build_scoped_method_call
(current_class_ref, vb, dtor_identifier,
build_expr_list (NULL_TREE, integer_zero_node)));
}
vbases = TREE_CHAIN (vbases);
}
expand_end_cond ();
}
do_pending_stack_adjust ();
if (cond != integer_one_node)
expand_end_cond ();
}
virtual_size = c_sizeof (current_class_type);
/* At the end, call delete if that's what's requested. */
/* FDIS sez: At the point of definition of a virtual destructor
(including an implicit definition), non-placement operator
delete shall be looked up in the scope of the destructor's
class and if found shall be accessible and unambiguous.
This is somewhat unclear, but I take it to mean that if the
class only defines placement deletes we don't do anything here.
So we pass LOOKUP_SPECULATIVELY; delete_sanity will complain
for us if they ever try to delete one of these. */
if (TYPE_GETS_REG_DELETE (current_class_type)
|| TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
exprstmt = build_op_delete_call
(DELETE_EXPR, current_class_ptr, virtual_size,
LOOKUP_NORMAL | LOOKUP_SPECULATIVELY, NULL_TREE);
else
exprstmt = NULL_TREE;
if (exprstmt)
{
cond = build (BIT_AND_EXPR, integer_type_node,
in_charge_node, integer_one_node);
expand_start_cond (cond, 0);
expand_expr_stmt (exprstmt);
expand_end_cond ();
}
/* End of destructor. */
expand_end_bindings (NULL_TREE, getdecls () != NULL_TREE, 0);
poplevel (getdecls () != NULL_TREE, 0, 0);
/* Back to the top of destructor. */
/* Don't execute destructor code if `this' is NULL. */
start_sequence ();
/* If the dtor is empty, and we know there is not possible way we
could use any vtable entries, before they are possibly set by
a base class dtor, we don't have to setup the vtables, as we
know that any base class dtoring will set up any vtables it
needs. We avoid MI, because one base class dtor can do a
virtual dispatch to an overridden function that would need to
have a non-related vtable set up, we cannot avoid setting up
vtables in that case. We could change this to see if there is
just one vtable. */
if (! empty_dtor || TYPE_USES_COMPLEX_INHERITANCE (current_class_type))
{
/* Make all virtual function table pointers in non-virtual base
classes point to CURRENT_CLASS_TYPE's virtual function
tables. */
expand_direct_vtbls_init (binfo, binfo, 1, 0, current_class_ptr);
if (TYPE_USES_VIRTUAL_BASECLASSES (current_class_type))
expand_indirect_vtbls_init (binfo, current_class_ref, current_class_ptr);
}
if (! ok_to_optimize_dtor)
{
cond = build_binary_op (NE_EXPR,
current_class_ptr, integer_zero_node);
expand_start_cond (cond, 0);
}
insns = get_insns ();
end_sequence ();
last_parm_insn = get_first_nonparm_insn ();
if (last_parm_insn == NULL_RTX)
last_parm_insn = get_last_insn ();
else
last_parm_insn = previous_insn (last_parm_insn);
emit_insns_after (insns, last_parm_insn);
if (! ok_to_optimize_dtor)
expand_end_cond ();
}
finish_dtor ();
else if (current_function_assigns_this)
{
/* Does not need to call emit_base_init, because
@ -14234,67 +14411,9 @@ finish_function (lineno, flags, nested)
current_function_just_assigned_this = 0;
base_init_expr = NULL_TREE;
}
else if (DECL_CONSTRUCTOR_P (fndecl))
{
tree cond = NULL_TREE, thenclause = NULL_TREE;
/* Allow constructor for a type to get a new instance of the object
using `build_new'. */
tree abstract_virtuals = CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type);
CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type) = NULL_TREE;
if (flag_this_is_variable > 0)
{
cond = build_binary_op (EQ_EXPR,
current_class_ptr, integer_zero_node);
thenclause = build_modify_expr (current_class_ptr, NOP_EXPR,
build_new (NULL_TREE, current_class_type, void_type_node, 0));
}
CLASSTYPE_ABSTRACT_VIRTUALS (current_class_type) = abstract_virtuals;
start_sequence ();
if (flag_this_is_variable > 0)
{
expand_start_cond (cond, 0);
expand_expr_stmt (thenclause);
expand_end_cond ();
}
/* Emit insns from `emit_base_init' which sets up virtual
function table pointer(s). */
if (base_init_expr)
{
expand_expr_stmt (base_init_expr);
base_init_expr = NULL_TREE;
}
insns = get_insns ();
end_sequence ();
/* This is where the body of the constructor begins. */
emit_insns_after (insns, last_parm_cleanup_insn);
end_protect_partials ();
/* This is where the body of the constructor ends. */
expand_label (ctor_label);
ctor_label = NULL_TREE;
if (call_poplevel)
{
decls = getdecls ();
expand_end_bindings (decls, decls != NULL_TREE, 0);
poplevel (decls != NULL_TREE, 1, 0);
}
/* c_expand_return knows to return 'this' from a constructor. */
c_expand_return (NULL_TREE);
current_function_assigns_this = 0;
current_function_just_assigned_this = 0;
}
else if (DECL_CONSTRUCTOR_P (fndecl)
&& !DECL_VLIST_CTOR_WRAPPER_P (fndecl))
finish_ctor (call_poplevel);
else if (DECL_MAIN_P (fndecl))
{
/* Make it so that `main' always returns 0 by default. */

233
contrib/gcc/cp/gxxint.texi
View File

@ -27,6 +27,7 @@ Questions and comments to Benjamin Kosnik @code{<bkoz@@cygnus.com>}.
* Exception Handling::
* Free Store::
* Mangling:: Function name mangling for C++ and Java
* Vtables:: Two ways to do virtual functions
* Concept Index::
@end menu
@ -191,7 +192,9 @@ accessed by the BINFO_ accessor macros.
The virtual function table holds information used in virtual function
dispatching. In the compiler, they are usually referred to as vtables,
or vtbls. The first index is not used in the normal way, I believe it
is probably used for the virtual destructor.
is probably used for the virtual destructor. There are two forms of
virtual tables, one that has offsets in addition to pointers, and one
using thunks. @xref{Vtables}.
@item vfield
@ -1456,7 +1459,7 @@ To meet the first goal, we defer emission of inlines and vtables until
the end of the translation unit, where we can decide whether or not they
are needed, and how to emit them if they are.
@node Mangling, Concept Index, Free Store, Top
@node Mangling, Vtables, Free Store, Top
@section Function name mangling for C++ and Java
Both C++ and Jave provide overloaded function and methods,
@ -1840,7 +1843,231 @@ Used for template type parameters.
The letters @samp{G}, @samp{M}, @samp{O}, and @samp{p}
also seem to be used for obscure purposes ...
@node Concept Index, , Mangling, Top
@node Vtables, Concept Index, Mangling, Top
@section Virtual Tables
In order to invoke virtual functions, GNU C++ uses virtual tables. Each
virtual function gets an index, and the table entry points to the
overridden function to call. Sometimes, and adjustment to the this
pointer has to be made before calling a virtual function:
@example
struct A@{
int i;
virtual void foo();
@};
struct B@{
int j;
virtual void bar();
@};
struct C:A,B@{
virtual void bar();
@};
void C::bar()
@{
i++;
@}
int main()
@{
C *c = new C;
B *b = c;
c->bar();
@}
@end example
Here, casting from @samp{c} to @samp{b} adds an offset. When @samp{bar}
is called, this offset needs to be subtracted, so that @samp{C::bar} can
properly access @samp{i}. One approach of achieving this is to use
@emph{thunks}, which are small half-functions put into the virtual
table. The modify the first argument (the @samp{this} pointer), and then
jump into the real function.
The other (traditional) approach is to have an additional integer in the
virtual table which is added to this. This is an additional overhead
both at the function call, and in the size of virtual tables: In the
case of single inheritance (or for the first base class), these integers
will always be zero.
@subsection Virtual Base Classes with Virtual Tables
In case of virtual bases, the code is even more
complicated. Constructors and destructors need to know whether they are
"in charge" of the virtual bases, and an implicit integer
@samp{__in_chrg} for that purpose.
@example
struct A@{
int i;
virtual void bar();
void call_bar()@{bar();@}
@};
struct B:virtual A@{
B();
int j;
virtual void bar();
@};
B::B()@{
call_bar();
@}
struct C@{
int k;
@};
struct D:C,B@{
int l;
virtual void bar();
@};
@end example
When constructing an instance of B, it will have the following layout:
@samp{vbase pointer to A}, @samp{j}, @samp{A virtual table}, @samp{i}.
On a 32-bit machine, downcasting from @samp{A*} to @samp{B*} would need
to subtract 8, which would be the thunk executed when calling
@samp{B::bar} inside @samp{call_bar}.
When constructing an instance of D, it will have a different layout:
@samp{k}, @samp{vbase pointer to A}, @samp{j}, @samp{l}, @samp{A virtual
table}, @samp{i}. So, when downcasting from @samp{A*} to @samp{B*} in a
@samp{D} object, the offset would be @samp{12}.
This means that during construction of the @samp{B} base of a @samp{D}
object, a virtual table is needed which has a @samp{-12} thunk to
@samp{B::bar}. This is @emph{only} needed during construction and
destruction, as the full object will use a @samp{-16} thunk to
@samp{D::bar}.
In order to implement this, the compiler generates an implicit argument
(in addition to @code{__in_chrg}): the virtual list argument
@code{__vlist}. This is a list of virtual tables needed during
construction and destruction. The virtual pointers are ordered in the
way they are used during construction; the destructors will process the
array in reverse order. The ordering is as follows:
@itemize @bullet
@item
If the class is in charge, the vlist starts with virtual table pointers
for the virtual bases that have virtual bases themselves. Here, only
@emph{polymorphic} virtual bases (pvbases) are interesting: if a vbase
has no virtual functions, it doesn't have a virtual table.
@item
Next, the vlist has virtual tables for the initialization of the
non-virtual bases. These bases are not in charge, so the layout is
recursive, but ignores virtual bases during recursion.
@item
Next, there is a number of virtual tables for each virtual base. These
are sorted in the order in which virtual bases are constructed. Each
virtual base may have more than one @code{vfield}, and therefore require
more than one @code{vtable}. The order of vtables is the same as used
when initializing vfields of non-virtual bases in a constructor.
@end itemize
The compiler emits a virtual table list in a variable mangled as
@code{__vl.classname}.
Class with virtual bases, but without pvbases, only have the
@code{__in_chrg} argument to their ctors and dtors: they don't have any
vfields in the vbases to initialize.
A further problem arises with virtual destructors: A destructor
typically has only the @code{__in_chrg} argument, which also indicates
whether the destructor should call @code{operator delete}. A dtor of a
class with pvbases has an additional argument. Unfortunately, a caller
of a virtual dtor might not know whether to pass that argument or not.
Therefore, the dtor processes the @code{__vlist} argument in an
automatic variable, which is initialized from the class' vlist if the
__in_chrg flag has a zero value in bit 2 (bit mask 4), or from the
argument @code{__vlist1} if bit 2 of the __in_chrg parameter is set to
one.
@subsection Specification of non-thunked vtables
In the traditional implementation of vtables, each slot contains three
fields: The offset to be added to the this pointer before invoking a
virtual function, an unused field that is always zero, and the pointer
to the virtual function. The first two fields are typically 16 bits
wide. The unused field is called `index'; it may be non-zero in
pointer-to-member-functions, which use the same layout.
The virtual table then is an array of vtable slots. The first slot is
always the virtual type info function, the other slots are in the order
in which the virtual functions appear in the class declaration.
If a class has base classes, it may inherit other bases' vfields. Each
class may have a primary vfield; the primary vfield of the derived class
is the primary vfield of the left-most non-virtual base class. If a
class inherits a primary vfield, any new virtual functions in the
derived class are appended to the virtual table of the primary
vfield. If there are new virtual functions in the derived class, and no
primary vfield is inherited, a new vfield is introduced which becomes
primary. The redefined virtual functions fill the vtable slots inherited
from the base; new virtual functions are put into the primary vtable in
the order of declaration. If no new virtual functions are introduced, no
primary vfield is allocated.
In a base class that has pvbases, virtual tables are needed which are
used only in the constructor (see example above). At run-time, the
virtual tables of the base class are adjusted, to reflect the new offset
of the pvbase. The compiler knows statically what offset the pvbase has
for a complete object. At run-time, the offset of the pvbase can be
extracted from the vbase pointer, which is set in the constructor of the
complete object. These two offsets result in a delta, which is used to
adjust the deltas in the vtable (the adjustment might be different for
different vtable slots). To adjust the vtables, the compiler emits code
that creates a vtable on the stack. This vtable is initialized with the
vtable for the complete base type, and then adjusted.
In order to call a virtual function, the compiler gets the offset field
from the vtable entry, and adds it to the this pointer. It then
indirectly calls the virtual function pointer, passing the adjusted this
pointer, and any arguments the virtual function may have.
To implement dynamic casting, the dynamic_cast function needs typeinfos
for the complete type, and the pointer to the complete type. The
typeinfo pointer is obtained by calling the virtual typeinfo function
(which doesn't take a this parameter). The pointer to the complete
object is obtained by adding the offset of the virtual typeinfo vtable
slot, since this virtual function is always implemented in the complete
object.
@subsection Specification of thunked vtables
For vtable thunks, each slot only consists of a pointer to the virtual
function, which might be a thunk function. The first slot in the vtable
is an offset of the this pointer to the complete object, which is needed
as a parameter to __dynamic_cast. The second slot is the virtual
typeinfo function. All other slots are allocated with the same procedure
as in the non-thunked case. Allocation of vfields also uses the same
procedure as described above.
If the virtual function needs an adjusted this pointer, a thunk function
is emitted. If supported by the target architecture, this is only a
half-function. Such a thunk has no stack frame; it merely adjusts the
first argument of the function, and then directly branches into the
implementation of the virtual function. If the architecture does not
support half-functions (i.e. if ASM_OUTPUT_MI_THUNK is not defined), the
compiler emits a wrapper function, which copies all arguments, adjust
the this pointer, and then calls the original function. Since objects of
non-aggregate type are passed by invisible reference, this copies only
POD arguments. The approach fails for virtual functions with a variable
number of arguments.
In order to support the vtables needed in base constructors with
pvbases, the compiler passes an implicit __vlist argument as described
above, if the version 2 thunks are used. For version 1 thunks, the base
class constructor will fill in the vtables for the complete base class,
which will incorrectly adjust the this pointer, leading to a dynamic
error.
@node Concept Index, , Vtables, Top
@section Concept Index

59
contrib/gcc/function.c
View File

@ -6704,7 +6704,10 @@ void
thread_prologue_and_epilogue_insns (f)
rtx f ATTRIBUTE_UNUSED;
{
int insertted = 0;
int inserted = 0;
#ifdef HAVE_prologue
rtx prologue_end = NULL_RTX;
#endif
prologue = 0;
#ifdef HAVE_prologue
@ -6721,7 +6724,7 @@ thread_prologue_and_epilogue_insns (f)
seq = get_insns ();
prologue = record_insns (seq);
emit_note (NULL, NOTE_INSN_PROLOGUE_END);
prologue_end = emit_note (NULL, NOTE_INSN_PROLOGUE_END);
seq = gen_sequence ();
end_sequence ();
@ -6734,7 +6737,7 @@ thread_prologue_and_epilogue_insns (f)
abort ();
insert_insn_on_edge (seq, ENTRY_BLOCK_PTR->succ);
insertted = 1;
inserted = 1;
}
else
emit_insn_after (seq, f);
@ -6866,8 +6869,56 @@ thread_prologue_and_epilogue_insns (f)
}
#endif
if (insertted)
if (inserted)
commit_edge_insertions ();
#ifdef HAVE_prologue
if (prologue_end)
{
rtx insn, prev;
/* GDB handles `break f' by setting a breakpoint on the first
line note *after* the prologue. Which means (1) that if
there are line number notes before where we inserted the
prologue we should move them, and (2) if there is no such
note, then we should generate one at the prologue. */
for (insn = prologue_end; insn ; insn = prev)
{
prev = PREV_INSN (insn);
if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) > 0)
{
/* Note that we cannot reorder the first insn in the
chain, since rest_of_compilation relies on that
remaining constant. Do the next best thing. */
if (prev == NULL)
{
emit_line_note_after (NOTE_SOURCE_FILE (insn),
NOTE_LINE_NUMBER (insn),
prologue_end);
NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
}
else
reorder_insns (insn, insn, prologue_end);
}
}
insn = NEXT_INSN (prologue_end);
if (! insn || GET_CODE (insn) != NOTE || NOTE_LINE_NUMBER (insn) <= 0)
{
for (insn = next_active_insn (f); insn ; insn = PREV_INSN (insn))
{
if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) > 0)
{
emit_line_note_after (NOTE_SOURCE_FILE (insn),
NOTE_LINE_NUMBER (insn),
prologue_end);
break;
}
}
}
}
#endif
}
/* Reposition the prologue-end and epilogue-begin notes after instruction

18
contrib/gcc/invoke.texi
View File

@ -1190,7 +1190,7 @@ anachronism. Therefore, by default it is invalid to assign to
type @samp{X *}. However, for backwards compatibility, you can make it
valid with @samp{-fthis-is-variable}.
@item -fvtable-thunks
@item -fvtable-thunks=@var{thunks-version}
Use @samp{thunks} to implement the virtual function dispatch table
(@samp{vtable}). The traditional (cfront-style) approach to
implementing vtables was to store a pointer to the function and two
@ -1198,13 +1198,27 @@ offsets for adjusting the @samp{this} pointer at the call site. Newer
implementations store a single pointer to a @samp{thunk} function which
does any necessary adjustment and then calls the target function.
The original implementation of thunks (version 1) had a bug regarding
virtual base classes; this bug is fixed with version 2 of the thunks
implementation. With setting the version to 2, compatibility to the
version 1 thunks is provided, at the cost of extra machine code. Version
3 does not include this compatibility.
This option also enables a heuristic for controlling emission of
vtables; if a class has any non-inline virtual functions, the vtable
will be emitted in the translation unit containing the first one of
those.
Like all options that change the ABI, all C++ code, @emph{including
libgcc.a} must be built with the same setting of this option.
libgcc.a} must be built with the same setting of this option. Since
version 1 and version 2 are also incompatible (for classes with virtual
bases defining virtual functions), all code must also be compiled with
the same version.
On some targets (e.g. Linux/GNU), version 2 thunks are the default. On these
targets, no option or -fvtable-thunks will produce version 2 thunks. On
all other targets, not giving the option will use the traditional
implementation, and -fvtable-thunks will produce version 2 thunks.
@item -nostdinc++
Do not search for header files in the standard directories specific to