PR c++/47346 - access control for nested type is ignored in template

Hello,

Consider this code snippet:

    class C
    {
      struct Private { };
    };

    template<typename T>
    struct exploit1
    {
      C::Private type;
    };

    exploit1<int> x1;   //#1

At the instantiation point of exploit1<int> in #1, the compiler should
issue an error because C::Private is private in that context.

The infrastructure I have added a while back to do access checking of
references to types like this was limited to typedefs only.  This bug
seems to suggest that the access checking of references to types, at
template instantiation should be done for references to all types, not
just typedefs.

But then, consider this other example:

    class C
    {
      struct Private { };
    };

    template<typename T>
    struct exploit2 : C::Private
    {
    };

    exploit2<int> x2;

g++ should warn here too, because access to C::Private is private in
this context.  The problem is when
add_typedef_to_current_template_for_access_check is called (from
check_accessibility_of_qualified_id), during the parsing of the class
header, the "current template" representing exploit2 is not yet
created.  So the reference to C::Private cannot be added to that
not-yet created template.

The patch below loosens the existing typedefs access checking
mechanisms to make it work for all type references, and defers the
scheduling of that access checking when the relevant template is not
yet created, until it becomes available.

It also adjusts two test cases that were using similar invalid
constructs that are now caught by the compiler.

Tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp/

	* cp-tree.h (struct qualified_type_usage_s):  Renamed struct
	qualified_typedef_usage_s into this.
	(qualified_type_usage_t): Renamed qualified_typedef_usage_t into
	this.
	(struct tree_template_info::type_needing_access_checking):
	Renamed typedefs_needing_access_checking into this.
	(TI_TYPES_NEEDING_ACCESS_CHECKING): Renamed
	TI_TYPEDEFS_NEEDING_ACCESS_CHECKING into this.
	(add_type_decl_to_current_template_for_access_check): Renamed
	add_typedef_to_current_template_for_access_check into this.
	(cp_parsing_class_head, cp_no_type_access_check_p): Declare new public
	global variables.
	(defer_type_access_check_for_cur_template)
	(schedule_deferred_access_check_types_for_template): New
	functions.
	* semantics.c
	(add_type_decl_to_current_template_for_access_check): Renamed
	add_typedef_to_current_template_for_access_check into this.  Make
	it accept potentially accesses to all types, not just typedefs.
	Make it defer the adding of the type access to the relevant
	template when said template is not yet available.
	(check_accessibility_of_qualified_id): Adjust.
	* decl.c (make_typename_type): Adjust.
	* parser.c (cp_parsing_class_head, cp_no_type_access_check_p):
	Define new public global variables.
	(cp_parser_elaborated_type_specifier): Don't schedule access
	checks for qualified type names of friend declaration, when in a
	template context.
	(cp_parser_class_specifier_1): Schedule qualified type names
	access check for type names access that happened while parsing the
	class head of a class template.
	(cp_parser_class_head): Notify the world when we are parsing a
	class head.
	* pt.c (cur_template_deferred_types_to_access_check): Define new
	global static variable.
	(perform_types_access_check): Renamed
	perform_typedefs_access_check into this and adjust the body.
	(instantiate_class_template_1, get_types_needing_access_check)
	(append_type_to_template_for_access_check_1)
	(append_type_to_template_for_access_check): Adjust.
	(defer_type_access_check_for_cur_template)
	(schedule_deferred_access_check_types_for_template): Define new
	functions.

gcc/testsuite/

	* g++.dg/template/access23.C: New test case.
	* g++.dg/lto/20081219_1.C: Adjust.
	* g++.dg/lto/20091002-1_0.C: Likewise.
---
 gcc/cp/cp-tree.h                         |   27 +++++----
 gcc/cp/decl.c                            |    4 +-
 gcc/cp/parser.c                          |   27 ++++++++-
 gcc/cp/pt.c                              |   92 +++++++++++++++++++++++-------
 gcc/cp/semantics.c                       |   59 ++++++++++++-------
 gcc/testsuite/g++.dg/lto/20081219_1.C    |    1 +
 gcc/testsuite/g++.dg/lto/20091002-1_0.C  |    1 +
 gcc/testsuite/g++.dg/template/access23.C |   33 +++++++++++
 8 files changed, 187 insertions(+), 57 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/access23.C

PR c++/47346 - access control for nested type is ignored in template

Commit Message

Patch