/* Help friends in C++.
Copyright (C) 1997-2023 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "cp-tree.h"
/* Friend data structures are described in cp-tree.h. */
/* The GLOBAL_FRIEND scope (functions, classes, or templates) is
regarded as a friend of every class. This is only used by libcc1,
to enable GDB's code snippets to access private members without
disabling access control in general, which could cause different
template overload resolution results when accessibility matters
(e.g. tests for an accessible member). */
static GTY(()) tree global_friend;
/* Set the GLOBAL_FRIEND for this compilation session. It might be
set multiple times, but always to the same scope. */
void
set_global_friend (tree scope)
{
gcc_checking_assert (scope != NULL_TREE);
gcc_assert (!global_friend || global_friend == scope);
global_friend = scope;
}
/* Return TRUE if SCOPE is the global friend. */
bool
is_global_friend (tree scope)
{
gcc_checking_assert (scope != NULL_TREE);
if (global_friend == scope)
return true;
if (!global_friend)
return false;
if (is_specialization_of_friend (global_friend, scope))
return true;
return false;
}
/* Returns nonzero if SUPPLICANT is a friend of TYPE. */
int
is_friend (tree type, tree supplicant)
{
int declp;
tree list;
tree context;
if (supplicant == NULL_TREE || type == NULL_TREE)
return 0;
if (is_global_friend (supplicant))
return 1;
declp = DECL_P (supplicant);
if (declp)
/* It's a function decl. */
{
tree list = DECL_FRIENDLIST (TYPE_MAIN_DECL (type));
tree name = DECL_NAME (supplicant);
for (; list ; list = TREE_CHAIN (list))
{
if (name == FRIEND_NAME (list))
{
tree friends = FRIEND_DECLS (list);
for (; friends ; friends = TREE_CHAIN (friends))
{
tree this_friend = TREE_VALUE (friends);
if (this_friend == NULL_TREE)
continue;
if (supplicant == this_friend)
return 1;
if (is_specialization_of_friend (supplicant, this_friend))
return 1;
}
break;
}
}
}
else
/* It's a type. */
{
if (same_type_p (supplicant, type))
return 1;
list = CLASSTYPE_FRIEND_CLASSES (TREE_TYPE (TYPE_MAIN_DECL (type)));
for (; list ; list = TREE_CHAIN (list))
{
tree t = TREE_VALUE (list);
if (TREE_CODE (t) == TEMPLATE_DECL ?
is_specialization_of_friend (TYPE_MAIN_DECL (supplicant), t) :
same_type_p (supplicant, t))
return 1;
}
}
if (declp)
{
if (DECL_FUNCTION_MEMBER_P (supplicant))
context = DECL_CONTEXT (supplicant);
else if (tree fc = DECL_FRIEND_CONTEXT (supplicant))
context = fc;
else
context = NULL_TREE;
}
else
{
if (TYPE_CLASS_SCOPE_P (supplicant))
/* Nested classes get the same access as their enclosing types, as
per DR 45 (this is a change from the standard). */
context = TYPE_CONTEXT (supplicant);
else
/* Local classes have the same access as the enclosing function. */
context = decl_function_context (TYPE_MAIN_DECL (supplicant));
}
/* A namespace is not friend to anybody. */
if (context && TREE_CODE (context) == NAMESPACE_DECL)
context = NULL_TREE;
if (context)
return is_friend (type, context);
return 0;
}
/* Add a new friend to the friends of the aggregate type TYPE.
DECL is the FUNCTION_DECL of the friend being added.
If COMPLAIN is true, warning about duplicate friend is issued.
We want to have this diagnostics during parsing but not
when a template is being instantiated. */
void
add_friend (tree type, tree decl, bool complain)
{
tree typedecl;
tree list;
tree name;
tree ctx;
if (decl == error_mark_node)
return;
typedecl = TYPE_MAIN_DECL (type);
list = DECL_FRIENDLIST (typedecl);
name = DECL_NAME (decl);
type = TREE_TYPE (typedecl);
while (list)
{
if (name == FRIEND_NAME (list))
{
tree friends = FRIEND_DECLS (list);
for (; friends ; friends = TREE_CHAIN (friends))
{
if (decl == TREE_VALUE (friends))
{
if (complain)
warning (OPT_Wredundant_decls,
"%qD is already a friend of class %qT",
decl, type);
return;
}
}
TREE_VALUE (list) = tree_cons (NULL_TREE, decl,
TREE_VALUE (list));
break;
}
list = TREE_CHAIN (list);
}
ctx = DECL_CONTEXT (decl);
if (ctx && CLASS_TYPE_P (ctx) && !uses_template_parms (ctx))
perform_or_defer_access_check (TYPE_BINFO (ctx), decl, decl,
tf_warning_or_error);
maybe_add_class_template_decl_list (type, decl, /*friend_p=*/1);
if (!list)
DECL_FRIENDLIST (typedecl)
= tree_cons (DECL_NAME (decl), build_tree_list (NULL_TREE, decl),
DECL_FRIENDLIST (typedecl));
if (!uses_template_parms (type))
DECL_BEFRIENDING_CLASSES (decl)
= tree_cons (NULL_TREE, type,
DECL_BEFRIENDING_CLASSES (decl));
}
/* Make FRIEND_TYPE a friend class to TYPE. If FRIEND_TYPE has already
been defined, we make all of its member functions friends of
TYPE. If not, we make it a pending friend, which can later be added
when its definition is seen. If a type is defined, then its TYPE_DECL's
DECL_UNDEFINED_FRIENDS contains a (possibly empty) list of friend
classes that are not defined. If a type has not yet been defined,
then the DECL_WAITING_FRIENDS contains a list of types
waiting to make it their friend. Note that these two can both
be in use at the same time!
If COMPLAIN is true, warning about duplicate friend is issued.
We want to have this diagnostics during parsing but not
when a template is being instantiated. */
void
make_friend_class (tree type, tree friend_type, bool complain)
{
tree classes;
/* CLASS_TEMPLATE_DEPTH counts the number of template headers for
the enclosing class. FRIEND_DEPTH counts the number of template
headers used for this friend declaration. TEMPLATE_MEMBER_P,
defined inside the `if' block for TYPENAME_TYPE case, is true if
a template header in FRIEND_DEPTH is intended for DECLARATOR.
For example, the code
template struct A {
template struct B {
template template
friend class C::D;
};
};
will eventually give the following results
1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
2. FRIEND_DEPTH equals 2 (for `V' and `W').
3. TEMPLATE_MEMBER_P is true (for `W').
The friend is a template friend iff FRIEND_DEPTH is nonzero. */
int class_template_depth = template_class_depth (type);
int friend_depth = 0;
if (current_template_depth)
/* When processing a friend declaration at parse time, just compare the
current depth to that of the class template. */
friend_depth = current_template_depth - class_template_depth;
else
{
/* Otherwise, we got here from instantiate_class_template. Determine
the friend depth by looking at the template parameters used within
FRIEND_TYPE. */
gcc_checking_assert (class_template_depth == 0);
while (uses_template_parms_level (friend_type, friend_depth + 1))
++friend_depth;
}
if (! MAYBE_CLASS_TYPE_P (friend_type)
&& TREE_CODE (friend_type) != TEMPLATE_TEMPLATE_PARM)
{
/* N1791: If the type specifier in a friend declaration designates a
(possibly cv-qualified) class type, that class is declared as a
friend; otherwise, the friend declaration is ignored.
So don't complain in C++11 mode. */
if (cxx_dialect < cxx11)
pedwarn (input_location, complain ? 0 : OPT_Wpedantic,
"invalid type %qT declared %", friend_type);
return;
}
friend_type = cv_unqualified (friend_type);
if (check_for_bare_parameter_packs (friend_type))
return;
if (friend_depth)
{
/* [temp.friend] Friend declarations shall not declare partial
specializations. */
if (CLASS_TYPE_P (friend_type)
&& CLASSTYPE_TEMPLATE_SPECIALIZATION (friend_type)
&& uses_template_parms (friend_type))
{
error ("partial specialization %qT declared %",
friend_type);
return;
}
if (TYPE_TEMPLATE_INFO (friend_type)
&& !PRIMARY_TEMPLATE_P (TYPE_TI_TEMPLATE (friend_type)))
{
auto_diagnostic_group d;
error ("%qT is not a template", friend_type);
inform (location_of (friend_type), "previous declaration here");
if (TYPE_CLASS_SCOPE_P (friend_type)
&& CLASSTYPE_TEMPLATE_INFO (TYPE_CONTEXT (friend_type))
&& currently_open_class (TYPE_CONTEXT (friend_type)))
inform (input_location, "perhaps you need explicit template "
"arguments in your nested-name-specifier");
return;
}
}
/* It makes sense for a template class to be friends with itself,
that means the instantiations can be friendly. Other cases are
not so meaningful. */
if (!friend_depth && same_type_p (type, friend_type))
{
if (complain)
warning (0, "class %qT is implicitly friends with itself",
type);
return;
}
/* [temp.friend]
A friend of a class or class template can be a function or
class template, a specialization of a function template or
class template, or an ordinary (nontemplate) function or
class. */
if (!friend_depth)
;/* ok */
else if (TREE_CODE (friend_type) == TYPENAME_TYPE)
{
if (TREE_CODE (TYPENAME_TYPE_FULLNAME (friend_type))
== TEMPLATE_ID_EXPR)
{
/* template friend class T::X; */
/* [temp.friend]
Friend declarations shall not declare partial
specializations. */
error ("partial specialization %qT declared %",
friend_type);
return;
}
else
{
/* We will figure this out later. */
bool template_member_p = false;
tree ctype = TYPE_CONTEXT (friend_type);
tree name = TYPE_IDENTIFIER (friend_type);
tree decl;
/* We need to distinguish a TYPENAME_TYPE for the non-template
class B in
template friend class A::B;
vs for the class template B in
template template friend class A::B; */
if (current_template_depth
&& !uses_template_parms_level (ctype, current_template_depth))
template_member_p = true;
if (class_template_depth)
{
/* We rely on tsubst_friend_class to check the
validity of the declaration later. */
if (template_member_p)
friend_type
= make_unbound_class_template (ctype,
name,
current_template_parms,
tf_error);
else
friend_type
= make_typename_type (ctype, name, class_type, tf_error);
}
else
{
decl = lookup_member (ctype, name, 0, true, tf_warning_or_error);
if (!decl)
{
error ("%qT is not a member of %qT", name, ctype);
return;
}
if (template_member_p && !DECL_CLASS_TEMPLATE_P (decl))
{
auto_diagnostic_group d;
error ("%qT is not a member class template of %qT",
name, ctype);
inform (DECL_SOURCE_LOCATION (decl),
"%qD declared here", decl);
return;
}
if (!template_member_p && (TREE_CODE (decl) != TYPE_DECL
|| !CLASS_TYPE_P (TREE_TYPE (decl))))
{
auto_diagnostic_group d;
error ("%qT is not a nested class of %qT",
name, ctype);
inform (DECL_SOURCE_LOCATION (decl),
"%qD declared here", decl);
return;
}
friend_type = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));
}
}
}
else if (TREE_CODE (friend_type) == TEMPLATE_TYPE_PARM)
{
/* template friend class T; */
error ("template parameter type %qT declared %", friend_type);
return;
}
else if (TREE_CODE (friend_type) == TEMPLATE_TEMPLATE_PARM)
friend_type = TYPE_NAME (friend_type);
else if (!CLASSTYPE_TEMPLATE_INFO (friend_type))
{
/* template friend class A; where A is not a template */
error ("%q#T is not a template", friend_type);
return;
}
else
/* template friend class A; where A is a template */
friend_type = CLASSTYPE_TI_TEMPLATE (friend_type);
if (friend_type == error_mark_node)
return;
/* See if it is already a friend. */
for (classes = CLASSTYPE_FRIEND_CLASSES (type);
classes;
classes = TREE_CHAIN (classes))
{
tree probe = TREE_VALUE (classes);
if (TREE_CODE (friend_type) == TEMPLATE_DECL)
{
if (friend_type == probe)
{
if (complain)
warning (OPT_Wredundant_decls,
"%qD is already a friend of %qT", probe, type);
break;
}
}
else if (TREE_CODE (probe) != TEMPLATE_DECL)
{
if (same_type_p (probe, friend_type))
{
if (complain)
warning (OPT_Wredundant_decls,
"%qT is already a friend of %qT", probe, type);
break;
}
}
}
if (!classes)
{
maybe_add_class_template_decl_list (type, friend_type, /*friend_p=*/1);
CLASSTYPE_FRIEND_CLASSES (type)
= tree_cons (NULL_TREE, friend_type, CLASSTYPE_FRIEND_CLASSES (type));
if (TREE_CODE (friend_type) == TEMPLATE_DECL)
friend_type = TREE_TYPE (friend_type);
if (!uses_template_parms (type))
CLASSTYPE_BEFRIENDING_CLASSES (friend_type)
= tree_cons (NULL_TREE, type,
CLASSTYPE_BEFRIENDING_CLASSES (friend_type));
}
}
/* Record DECL (a FUNCTION_DECL) as a friend of the
CURRENT_CLASS_TYPE. If DECL is a member function, SCOPE is the
class of which it is a member, as named in the friend declaration.
If the friend declaration was explicitly namespace-qualified, SCOPE
is that namespace.
DECLARATOR is the name of the friend. FUNCDEF_FLAG is true if the
friend declaration is a definition of the function. FLAGS is as
for grokclass fn. */
tree
do_friend (tree scope, tree declarator, tree decl,
enum overload_flags flags,
bool funcdef_flag)
{
gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);
tree ctype = NULL_TREE;
tree in_namespace = NULL_TREE;
if (!scope)
;
else if (MAYBE_CLASS_TYPE_P (scope))
ctype = scope;
else
{
gcc_checking_assert (TREE_CODE (scope) == NAMESPACE_DECL);
in_namespace = scope;
}
/* Friend functions are unique, until proved otherwise. */
DECL_UNIQUE_FRIEND_P (decl) = 1;
if (DECL_OVERRIDE_P (decl) || DECL_FINAL_P (decl))
error ("friend declaration %qD may not have virt-specifiers",
decl);
tree orig_declarator = declarator;
if (TREE_CODE (declarator) == TEMPLATE_ID_EXPR)
{
declarator = TREE_OPERAND (declarator, 0);
if (!identifier_p (declarator))
declarator = OVL_NAME (declarator);
}
/* CLASS_TEMPLATE_DEPTH counts the number of template headers for
the enclosing class. FRIEND_DEPTH counts the number of template
headers used for this friend declaration. TEMPLATE_MEMBER_P is
true if a template header in FRIEND_DEPTH is intended for
DECLARATOR. For example, the code
template struct A {
template struct B {
template template
friend void C::f(W);
};
};
will eventually give the following results
1. CLASS_TEMPLATE_DEPTH equals 2 (for `T' and `U').
2. FRIEND_DEPTH equals 2 (for `V' and `W').
3. CTYPE_DEPTH equals 1 (for `V').
4. TEMPLATE_MEMBER_P is true (for `W'). */
int class_template_depth = template_class_depth (current_class_type);
int friend_depth = current_template_depth - class_template_depth;
int ctype_depth = num_template_headers_for_class (ctype);
bool template_member_p = friend_depth > ctype_depth;
if (ctype)
{
tree cname = TYPE_NAME (ctype);
if (TREE_CODE (cname) == TYPE_DECL)
cname = DECL_NAME (cname);
/* A method friend. */
if (flags == NO_SPECIAL && declarator == cname)
DECL_CXX_CONSTRUCTOR_P (decl) = 1;
grokclassfn (ctype, decl, flags);
/* A nested class may declare a member of an enclosing class
to be a friend, so we do lookup here even if CTYPE is in
the process of being defined. */
if (class_template_depth
|| COMPLETE_OR_OPEN_TYPE_P (ctype))
{
if (DECL_TEMPLATE_INFO (decl))
/* DECL is a template specialization. No need to
build a new TEMPLATE_DECL. */
;
else if (class_template_depth)
/* We rely on tsubst_friend_function to check the
validity of the declaration later. */
decl = push_template_decl (decl, /*is_friend=*/true);
else
decl = check_classfn (ctype, decl,
template_member_p
? current_template_parms
: NULL_TREE);
if ((template_member_p
/* Always pull out the TEMPLATE_DECL if we have a friend
template in a class template so that it gets tsubsted
properly later on (59956). tsubst_friend_function knows
how to tell this apart from a member template. */
|| (class_template_depth && friend_depth))
&& decl && TREE_CODE (decl) == FUNCTION_DECL)
decl = DECL_TI_TEMPLATE (decl);
}
else
error ("member %qD declared as friend before type %qT defined",
decl, ctype);
}
else
{
/* Namespace-scope friend function. */
if (funcdef_flag)
SET_DECL_FRIEND_CONTEXT (decl, current_class_type);
if (! DECL_USE_TEMPLATE (decl))
{
/* We must check whether the decl refers to template
arguments before push_template_decl adds a reference to
the containing template class. */
int warn = (warn_nontemplate_friend
&& ! funcdef_flag && ! friend_depth
&& current_template_parms
&& uses_template_parms (decl));
if (friend_depth || class_template_depth)
/* We can't call pushdecl for a template class, since in
general, such a declaration depends on template
parameters. Instead, we call pushdecl when the class
is instantiated. */
decl = push_template_decl (decl, /*is_friend=*/true);
else if (current_function_decl && !in_namespace)
/* pushdecl will check there's a local decl already. */
decl = pushdecl (decl, /*hiding=*/true);
else
{
/* We can't use pushdecl, as we might be in a template
class specialization, and pushdecl will insert an
unqualified friend decl into the template parameter
scope, rather than the namespace containing it. */
tree ns = decl_namespace_context (decl);
push_nested_namespace (ns);
decl = pushdecl_namespace_level (decl, /*hiding=*/true);
pop_nested_namespace (ns);
}
if (warn)
{
static int explained;
bool warned;
auto_diagnostic_group d;
warned = warning (OPT_Wnon_template_friend, "friend declaration "
"%q#D declares a non-template function", decl);
if (! explained && warned)
{
inform (input_location, "(if this is not what you intended, "
"make sure the function template has already been "
"declared and add %<<>%> after the function name "
"here)");
explained = 1;
}
}
}
}
if (decl == error_mark_node)
return error_mark_node;
if (!class_template_depth && DECL_IMPLICIT_INSTANTIATION (decl))
/* "[if no non-template match is found,] each remaining function template
is replaced with the specialization chosen by deduction from the
friend declaration or discarded if deduction fails."
set_decl_namespace or check_classfn set DECL_IMPLICIT_INSTANTIATION to
indicate that we need a template match, so ask
check_explicit_specialization to find one. */
decl = (check_explicit_specialization
(orig_declarator, decl, ctype_depth,
2 * funcdef_flag + 4));
add_friend (current_class_type,
(!ctype && friend_depth) ? DECL_TI_TEMPLATE (decl) : decl,
/*complain=*/true);
return decl;
}
#include "gt-cp-friend.h"