[gcc r11-7789] c++: Fix bogus warning in deprecated namespace [PR99318]

[Marek Polacek]

https://gcc.gnu.org/g:831f9f768eb1fbf9a31d9a89591188b1487b6376

commit r11-7789-g831f9f768eb1fbf9a31d9a89591188b1487b6376
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Mar 9 19:23:48 2021 -0500

    c++: Fix bogus warning in deprecated namespace [PR99318]
    
    In GCC 10, I introduced cp_warn_deprecated_use_scopes so that we can
    handle attribute deprecated on a namespace declaration.  This
    function walks the decl's contexts so that we warn for code like
    
      namespace [[deprecated]] N { struct S { }; }
      N::S s;
    
    We call cp_warn_deprecated_use_scopes when we encounter a TYPE_DECL.
    But in the following testcase we have a TYPE_DECL whose context is
    a deprecated function; that itself is not a reason to warn.  This
    patch limits for which entities we call cp_warn_deprecated_use;
    essentially it's what can follow ::.
    
    I noticed that we didn't test that
    
      struct [[deprecated]] S { static void fn(); };
      S::fn();
    
    produces the expected warning, so I've added gen-attrs-73.C.
    
    gcc/cp/ChangeLog:
    
            PR c++/99318
            * decl2.c (cp_warn_deprecated_use_scopes): Only call
            cp_warn_deprecated_use when decl is a namespace, class, or enum.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/99318
            * g++.dg/cpp0x/attributes-namespace6.C: New test.
            * g++.dg/cpp0x/gen-attrs-73.C: New test.

Diff:
---
 gcc/cp/decl2.c                                     |  3 ++-
 gcc/testsuite/g++.dg/cpp0x/attributes-namespace6.C | 21 +++++++++++++++++++++
 gcc/testsuite/g++.dg/cpp0x/gen-attrs-73.C          | 20 ++++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index c46100de89a..ef79f6cc6d1 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -5529,7 +5529,8 @@ cp_warn_deprecated_use_scopes (tree scope)
 	 && scope != error_mark_node
 	 && scope != global_namespace)
     {
-      if (cp_warn_deprecated_use (scope))
+      if ((TREE_CODE (scope) == NAMESPACE_DECL || OVERLOAD_TYPE_P (scope))
+	  && cp_warn_deprecated_use (scope))
 	return;
       if (TYPE_P (scope))
 	scope = CP_TYPE_CONTEXT (scope);
diff --git a/gcc/testsuite/g++.dg/cpp0x/attributes-namespace6.C b/gcc/testsuite/g++.dg/cpp0x/attributes-namespace6.C
new file mode 100644
index 00000000000..2fbc8e1158f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/attributes-namespace6.C
@@ -0,0 +1,21 @@
+// PR c++/99318
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct S {
+    [[deprecated("foo")]] unsigned m_fn (char const chr)
+    {
+        using index_t = unsigned;
+        return T::arr[static_cast<index_t>(chr)]; // { dg-bogus "deprecated" }
+    }
+};
+
+extern unsigned int arr[];
+
+struct R {
+    [[deprecated("foo")]] unsigned m_fn (char const chr)
+    {
+        using index_t = unsigned;
+        return arr[static_cast<index_t>(chr)]; // { dg-bogus "deprecated" }
+    }
+};
diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-73.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-73.C
new file mode 100644
index 00000000000..75f4077af7b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-73.C
@@ -0,0 +1,20 @@
+// { dg-do compile { target c++11 } }
+// Test attribute deprecated on :: with class, enum, and namespace.
+
+struct [[deprecated]] S { static void fn(); static const int s = 0; };
+union [[deprecated]] U { static void fn(); static const int u = 0; };
+enum [[deprecated]] E { X };
+enum class [[deprecated]] SE { Y };
+namespace [[deprecated]] N { struct S { }; }
+
+void
+g ()
+{
+  S::fn(); // { dg-warning "deprecated" }
+  (void) S::s; // { dg-warning "deprecated" }
+  U::fn(); // { dg-warning "deprecated" } 
+  (void) U::u; // { dg-warning "deprecated" }
+  (void) E::X; // { dg-warning "deprecated" }
+  (void) SE::Y; // { dg-warning "deprecated" }
+  N::S s; // { dg-warning "deprecated" }
+}