Hiya
> That's because none of the names are overloaded within a single base
> class.
Ah, thanks. Thought there must be something I wasn't thinking of.
> Also, you can use == instead of cp_tree_equal for comparing FUNCTION_DECLs.
Changed it.
Latest patch is attached. Compiles fine and no regressions.
Anthony
From 0b2dd8d8818c6e23b3c8d1b0de7b71c1bb86e6c3 Mon Sep 17 00:00:00 2001
From: Anthony Sharp <anthonyshar...@gmail.com>
Date: Wed, 10 Mar 2021 20:36:03 +0000
Subject: [PATCH] c++: Private parent access check for using decls [PR19377]
This bug was already mostly fixed by the patch for PR17314. This
patch continues that by ensuring that where a using decl is used,
causing an access failure to a child class because the using decl is
private, the compiler correctly points to the using decl as the
source of the problem.
gcc/cp/ChangeLog:
2021-03-10 Anthony Sharp <anthonyshar...@gmail.com>
* semantics.c (get_class_access_diagnostic_decl): New
function that examines special cases when a parent
class causes a private access failure.
(enforce_access): Slightly modified to call function
above.
gcc/testsuite/ChangeLog:
2021-03-10 Anthony Sharp <anthonyshar...@gmail.com>
* g++.dg/cpp1z/using9.C: New using decl test.
---
gcc/cp/semantics.c | 110 +++++++++++++++++++++++-----
gcc/testsuite/g++.dg/cpp1z/using9.C | 49 +++++++++++++
2 files changed, 141 insertions(+), 18 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/using9.C
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 73834467fca..f1a4f102408 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -256,6 +256,81 @@ pop_to_parent_deferring_access_checks (void)
}
}
+/* Called from enforce_access. A class has attempted (but failed) to access
+ DECL. It is already established that a baseclass of that class,
+ PARENT_BINFO, has private access to DECL. Examine certain special cases
+ to find a decl that accurately describes the source of the problem. If
+ none of the special cases apply, simply return DECL as the source of the
+ problem. */
+
+static tree
+get_class_access_diagnostic_decl (tree parent_binfo, tree decl)
+{
+ /* When a class is denied access to a decl in a baseclass, most of the
+ time it is because the decl itself was declared as private at the point
+ of declaration.
+
+ However, in C++, there are (at least) two situations in which a decl
+ can be private even though it was not originally defined as such.
+ These two situations only apply if a baseclass had private access to
+ DECL (this function is only called if that is the case). */
+
+ /* We should first check whether the reason the parent had private access
+ to DECL was simply because DECL was created and declared as private in
+ the parent. If it was, then DECL is definitively the source of the
+ problem. */
+ if (SAME_BINFO_TYPE_P (context_for_name_lookup (decl),
+ BINFO_TYPE (parent_binfo)))
+ return decl;
+
+ /* 1. If the "using" keyword is used to inherit DECL within the parent,
+ this may cause DECL to be private, so we should return the using
+ statement as the source of the problem.
+
+ Scan the fields of PARENT_BINFO and see if there are any using decls. If
+ there are, see if they inherit DECL. If they do, that's where DECL must
+ have been declared private. */
+
+ for (tree parent_field = TYPE_FIELDS (BINFO_TYPE (parent_binfo));
+ parent_field;
+ parent_field = DECL_CHAIN (parent_field))
+ {
+ /* Not necessary, but also check TREE_PRIVATE for the sake of
+ eliminating obviously non-relevant using decls. */
+ if (TREE_CODE (parent_field) == USING_DECL
+ && TREE_PRIVATE (parent_field))
+ {
+ tree decl_stripped = strip_using_decl (parent_field);
+
+ if (is_overloaded_fn (decl_stripped))
+ {
+ /* The using statement might be overloaded. If so, we need to
+ check all of the overloads. */
+ for (ovl_iterator iter (decl_stripped); iter; ++iter)
+ {
+ /* If equal, the using statement inherits DECL, and so is the
+ source of the access failure, so return it. */
+ if (*iter == decl)
+ return parent_field;
+ }
+ }
+ else if (decl_stripped == decl)
+ return parent_field;
+ }
+ }
+
+ /* 2. If DECL was privately inherited by the parent class, then DECL will
+ be inaccessible, even though it may originally have been accessible to
+ deriving classes. In that case, the fault lies with the parent, since it
+ used a private inheritance, so we return the parent as the source of the
+ problem.
+
+ Since this is the last check, we just assume it's true. At worst, it
+ will simply point to the class that failed to give access, which is
+ technically true. */
+ return TYPE_NAME (BINFO_TYPE (parent_binfo));
+}
+
/* If the current scope isn't allowed to access DECL along
BASETYPE_PATH, give an error, or if we're parsing a function or class
template, defer the access check to be performed at instantiation time.
@@ -317,34 +392,33 @@ enforce_access (tree basetype_path, tree decl, tree diag_decl,
diag_decl = strip_inheriting_ctors (diag_decl);
if (complain & tf_error)
{
- /* We will usually want to point to the same place as
- diag_decl but not always. */
+ access_kind access_failure_reason = ak_none;
+
+ /* By default, using the decl as the source of the problem will
+ usually give correct results. */
tree diag_location = diag_decl;
- access_kind parent_access = ak_none;
- /* See if any of BASETYPE_PATH's parents had private access
- to DECL. If they did, that will tell us why we don't. */
+ /* However, if a parent of BASETYPE_PATH had private access to decl,
+ then it actually might be the case that the source of the problem
+ is not DECL. */
tree parent_binfo = get_parent_with_private_access (decl,
basetype_path);
- /* If a parent had private access, then the diagnostic
- location DECL should be that of the parent class, since it
- failed to give suitable access by using a private
- inheritance. But if DECL was actually defined in the parent,
- it wasn't privately inherited, and so we don't need to do
- this, and complain_about_access will figure out what to
- do. */
- if (parent_binfo != NULL_TREE
- && (context_for_name_lookup (decl)
- != BINFO_TYPE (parent_binfo)))
+ /* So if a parent did have private access, then we need to do
+ special checks to obtain the best diagnostic location decl. */
+ if (parent_binfo != NULL_TREE)
{
- diag_location = TYPE_NAME (BINFO_TYPE (parent_binfo));
- parent_access = ak_private;
+ diag_location = get_class_access_diagnostic_decl (parent_binfo,
+ diag_decl);
+
+ /* We also at this point know that the reason access failed was
+ because decl was private. */
+ access_failure_reason = ak_private;
}
/* Finally, generate an error message. */
complain_about_access (decl, diag_decl, diag_location, true,
- parent_access);
+ access_failure_reason);
}
if (afi)
afi->record_access_failure (basetype_path, decl, diag_decl);
diff --git a/gcc/testsuite/g++.dg/cpp1z/using9.C b/gcc/testsuite/g++.dg/cpp1z/using9.C
new file mode 100644
index 00000000000..98e36babb01
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/using9.C
@@ -0,0 +1,49 @@
+/* { dg-do compile { target c++17 } } */
+// Created for c++ PR19377
+
+class A2
+{
+ protected:
+ int separate(int a);
+ int separate(int a, int b);
+ int separate(int a, int b, int c);
+ int comma(int a);
+ int alone;
+};
+
+class A1
+{
+ protected:
+ int separate();
+ int comma();
+};
+
+class A3
+{
+ protected:
+ int comma(int a, int b);
+};
+
+class B:private A3, private A1, private A2
+{
+ // Using decls in a comma-separated list.
+ using A2::comma, A3::comma, A1::comma; // { dg-message "declared" }
+ // Separate using statements.
+ using A2::separate; // { dg-message "declared" }
+ using A1::separate; // { dg-message "declared" }
+ // No ambiguity, just for the sake of it.
+ using A2::alone; // { dg-message "declared" }
+};
+
+class C:public B
+{
+ void f()
+ {
+ comma(); // { dg-error "private" }
+ separate(); // { dg-error "private" }
+ separate(1); // { dg-error "private" }
+ separate(1, 2); // { dg-error "private" }
+ separate(1, 2, 3); // { dg-error "private" }
+ alone = 5; // { dg-error "private" }
+ }
+};
--
2.25.1
