Hi,
a few comments:
On Fri, Feb 05, 2021 at 03:39:25PM +0000, Anthony Sharp via Gcc-patches wrote:
> 2021-02-05 Anthony Sharp <anthonyshar...@gmail.com>
>
> * semantics.c (get_class_access_diagnostic_decl): New function.
> (enforce_access): Altered function.
Pedantically, "Altered function." is not very good, it should say what
in enforce_access changed.
> gcc/testsuite/ChangeLog:
>
> 2021-02-05 Anthony Sharp <anthonyshar...@gmail.com>
>
> * g++.dg/pr19377.C: New test.
Let's move the test into g++.dg/cpp1z and call it using9.C.
> gcc/cp/semantics.c | 89 ++++++++++++++++++++++++++--------
> gcc/testsuite/g++.dg/pr19377.C | 28 +++++++++++
> 2 files changed, 98 insertions(+), 19 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/pr19377.C
>
> diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
> index 73834467fca..ffb627f08ea 100644
> --- a/gcc/cp/semantics.c
> +++ b/gcc/cp/semantics.c
> @@ -256,6 +256,58 @@ 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
> + generate a diagnostic decl location. If no special cases are found,
> simply
I don't understand the "generate a diagnostic decl location". Maybe just
"generate a diagnostic?"
> + return DECL. */
> +
> +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. So, by default, DECL is at fault.
> +
> + 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 must
> however
> + also ensure that the reason the parent had private access wasn't simply
> + because it was declared as private in the parent. */
These two comments can be merged into one.
> + if (context_for_name_lookup (decl) == BINFO_TYPE (parent_binfo))
> + return decl;
I think for comparing a binfo with a type we should use SAME_BINFO_TYPE_P.
> + /* 1. If the "using" keyword is used to inherit DECL within a baseclass,
> + this may cause DECL to be private, so we 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 was
> + truly declared private. */
> + for (tree parent_field = TYPE_FIELDS (BINFO_TYPE (parent_binfo));
> + parent_field;
> + parent_field = DECL_CHAIN (parent_field))
> + {
> + if ((TREE_CODE (parent_field) == USING_DECL)
This first term doesn't need to be wrapped in ().
> + && TREE_PRIVATE (parent_field))
> + {
> + if (DECL_NAME (decl) == DECL_NAME (parent_field))
This could be part of the if above. And then we can drop the braces (in the
if and for both).
> + return parent_field;
> + }
> + }
> +
> + /* 2. If decl was privately inherited by a baseclass of the current 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 baseclass that used a private inheritance, so we return the
> + baseclass type as the source of the problem.
> +
> + Since this is the last check, we just assume it's 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 +369,33 @@ 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);
> + 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 had private access, then we need to do special
Just "had" instead of "did had"?
> + 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;
Looks like this line is indented too much (even in the newer patch).
>
> /* 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/pr19377.C b/gcc/testsuite/g++.dg/pr19377.C
> new file mode 100644
> index 00000000000..fb023a33f82
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr19377.C
> @@ -0,0 +1,28 @@
> +/* { dg-do assemble } */
We usually use dg-do compile.
> +// { dg-options "-std=c++17" }
Best to replace both with
// { dg-do compile { target c++17 } }
> +class A
> +{
> + protected:
> + int i();
> +};
> +
> +class A2
> +{
> + protected:
> + int i(int a);
> +};
> +
> +class B:private A, private A2
> +{
> + // Comma separated list only officially supported in c++17 and later.
> + using A::i, A2::i; // { dg-message "declared" }
> +};
> +
> +class C:public B
> +{
> + void f()
> + {
> + i(); // { dg-error "private" }
> + }
> +};
> \ No newline at end of file
> --
> 2.25.1
>
Marek
