[PATCH] Fix PR c++/70218 (illegal access to private field succeeds)

[Patrick Palka]

Here we are mishandling the deferred_access_stack by not coherently
pushing/popping from it.  In cp_parser_lambda_expression we are calling
(in order):

  push_deferring_access_checks (dk_no_deferred);
  cp_parser_start_tentative_firewall (parser);
  ...
  pop_deferring_access_checks ();
  cp_parser_end_tentative_firewall (parser, start, lambda_expr);

But the order of the last two popping calls does not correspond with the order
of the first two pushing calls.  pop_deferring_access_checks should be
called last.  This error may cause us to drop deferred access checks
instead of performing them.

Bootstrap + regtest in progress, does this look OK to commit if testing
succeeds?

gcc/cp/ChangeLog:

        PR c++/70218
        * parser.c (cp_parser_lambda_expression): Move call to
        pop_deferring_access_checks ahead of the call to
        cp_parser_end_tentative_firewall.

gcc/testsuite/ChangeLog:

        PR c++/70218
        * g++.dg/cpp0x/lambda/lambda-70218.C: New test.
---
 gcc/cp/parser.c                                  |  4 ++--
 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-70218.C | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-70218.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 6ae45b0..33f09b8 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -9781,8 +9781,6 @@ cp_parser_lambda_expression (cp_parser* parser)
        = auto_is_implicit_function_template_parm_p;
   }
 
-  pop_deferring_access_checks ();
-
   /* This field is only used during parsing of the lambda.  */
   LAMBDA_EXPR_THIS_CAPTURE (lambda_expr) = NULL_TREE;
 
@@ -9798,6 +9796,8 @@ cp_parser_lambda_expression (cp_parser* parser)
 
   cp_parser_end_tentative_firewall (parser, start, lambda_expr);
 
+  pop_deferring_access_checks ();
+
   return lambda_expr;
 }
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-70218.C 
b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-70218.C
new file mode 100644
index 0000000..ae8cc2f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-70218.C
@@ -0,0 +1,17 @@
+// PR c++/70218
+// { dg-do compile { target c++11 } }
+
+struct X {
+private:
+   int i;
+};
+
+struct Y {
+  Y (int) { }
+};
+
+void
+foo ()
+{
+  Y ([] { X x; x.i = 3; return 0; } ()); // { dg-error "private" }
+}
-- 
2.8.0.rc1.12.gfce6d53