c++: Always check access during late-parsing of members [PR58993]

This patch removes a vestigial use of dk_no_check from
cp_parser_late_parsing_for_member, which ideally should have been
removed as part of the PR41437 patch that improved access checking
inside templates.  This allows us to correctly reject f1 and f2 in
the testcase access34.C below (whereas before we'd only reject f3).

Additional testing revealed a new access issue when late-parsing a hidden
friend within a class template.  In the testcase friend68.C below, we're
tripping over the checking assert from friend_accessible_p(f, S::j, S, S)
during lookup of j in x.j (for which type_dependent_object_expression_p
returns false, which is why we're doing the lookup at parse time).  The
reason for the assert failure is that DECL_FRIENDLIST(S) contains f but
DECL_BEFRIENDING_CLASSES(f) is empty, and so friend_accessible_p (which
looks at DECL_BEFRIENDING_CLASSES) wants to return false, but is_friend
(which looks at DECL_FRIENDLIST) returns true.

For sake of symmetry one would expect that DECL_BEFRIENDING_CLASSES(f)
contains S, but add_friend avoids updating DECL_BEFRIENDING_CLASSES when
the class type (S in this case) is dependent, for some reason.

This patch works around this issue by making friend_accessible_p
consider the DECL_FRIEND_CONTEXT of the access scope.  Thus we sidestep
the DECL_BEFRIENDING_CLASSES / DECL_FRIENDLIST asymmetry issue while
correctly validating the x.j access at parse time.

A earlier version of this patch checked friend_accessible_p instead of
protected_accessible_p in the DECL_FRIEND_CONTEXT hunk below, but this
had the side effect of making us accept the ill-formed testcase friend69.C
below (ill-formed because the hidden friend g is not actually a member
of A, so g doesn't have access to B's members despite B befriending A).

gcc/cp/ChangeLog:

	PR c++/41437
	PR c++/58993
	* search.c (friend_accessible_p): If scope is a hidden friend
	defined inside a dependent class, consider access from the
	class.
	* parser.c (cp_parser_late_parsing_for_member): Don't push a
	dk_no_check access state.

gcc/testsuite/ChangeLog:

	PR c++/41437
	PR c++/58993
	* g++.dg/opt/pr87974.C: Adjust.
	* g++.dg/template/access34.C: New test.
	* g++.dg/template/friend68.C: New test.
	* g++.dg/template/friend69.C: New test.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 5651cfacd3c727cc68852bd122a0ac3643341e1e..eeffc2e7ae3aa528fd3ef016dbc441a60de552b0 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -30823,10 +30823,6 @@ cp_parser_late_parsing_for_member (cp_parser* parser, tree member_function)
       start_preparsed_function (member_function, NULL_TREE,
                                SF_PRE_PARSED | SF_INCLASS_INLINE);
 
-      /* Don't do access checking if it is a templated function.  */
-      if (processing_template_decl)
-       push_deferring_access_checks (dk_no_check);
-
       /* #pragma omp declare reduction needs special parsing.  */
       if (DECL_OMP_DECLARE_REDUCTION_P (member_function))
        {
@@ -30840,9 +30836,6 @@ cp_parser_late_parsing_for_member (cp_parser* parser, tree member_function)
        cp_parser_function_definition_after_declarator (parser,
                                                        /*inline_p=*/true);
 
-      if (processing_template_decl)
-       pop_deferring_access_checks ();
-
       /* Leave the scope of the containing function.  */
       if (function_scope)
        pop_function_context ();

diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index 1a9dba451c7ec11617eeb0a7810fc0ad3b728b8a..dd3773da4f79ee44557368c97d324ea4d28c9474 100644 (file)
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -698,6 +698,14 @@ friend_accessible_p (tree scope, tree decl, tree type, tree otype)
       if (DECL_CLASS_SCOPE_P (scope)
          && friend_accessible_p (DECL_CONTEXT (scope), decl, type, otype))
        return 1;
+      /* Perhaps SCOPE is a friend function defined inside a class from which
+        DECL is accessible.  Checking this is necessary only when the class
+        is dependent, for otherwise add_friend will already have added the
+        class to SCOPE's DECL_BEFRIENDING_CLASSES.  */
+      if (tree fctx = DECL_FRIEND_CONTEXT (scope))
+       if (dependent_type_p (fctx)
+           && protected_accessible_p (decl, fctx, type, otype))
+         return 1;
     }
 
   /* Maybe scope's template is a friend.  */

diff --git a/gcc/testsuite/g++.dg/opt/pr87974.C b/gcc/testsuite/g++.dg/opt/pr87974.C
index 4b070d2a6f83f55f34a371b10244030c0f2a91c0..7d8357a025c7d8426f55bc349678b6339f735c4d 100644 (file)
--- a/gcc/testsuite/g++.dg/opt/pr87974.C
+++ b/gcc/testsuite/g++.dg/opt/pr87974.C
@@ -8,6 +8,7 @@ class i {
     struct j {
        using c = int *;
     };
+public:
     using as = j::c;
 };
 template <typename> class k {

diff --git a/gcc/testsuite/g++.dg/template/access34.C b/gcc/testsuite/g++.dg/template/access34.C
new file mode 100644 (file)
index 0000000..ec79f87
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/access34.C
@@ -0,0 +1,29 @@
+// PR c++/58993
+// { dg-do compile }
+
+class base { void foo(); };
+
+template <class T>
+struct bar : public base {
+  void f1() {
+    &base::foo;  // { dg-error "private" }
+  }
+
+  template <class>
+  void f2() {
+    &base::foo;  // { dg-error "private" }
+  }
+
+  void f3();
+};
+
+template <class T>
+void bar<T>::f3() {
+  (void) &base::foo; // { dg-error "private" }
+}
+
+int main() {
+  bar<int>().f1();
+  bar<int>().f2<int>();
+  bar<int>().f3();
+}

diff --git a/gcc/testsuite/g++.dg/template/friend68.C b/gcc/testsuite/g++.dg/template/friend68.C
new file mode 100644 (file)
index 0000000..fa34d2c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend68.C
@@ -0,0 +1,13 @@
+// { dg-do compile }
+
+template <class>
+struct S {
+  S();
+  friend int f(S x) { return x.i + x.j; }
+  template <class T>
+    friend int g(S x, T) { return x.i + x.j; }
+private:
+  int i;
+protected:
+  int j;
+};

diff --git a/gcc/testsuite/g++.dg/template/friend69.C b/gcc/testsuite/g++.dg/template/friend69.C
new file mode 100644 (file)
index 0000000..f3086a9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend69.C
@@ -0,0 +1,18 @@
+// { dg-do compile }
+
+struct A;
+
+struct B {
+  friend struct A;
+private:
+  static void f();
+protected:
+  static void g();
+};
+
+struct A {
+  friend void g(A) {
+    B::f(); // { dg-error "private" }
+    B::g(); // { dg-error "protected" }
+  }
+};