c++: Fix ICE on namespace attributes [PR123684]

The following testcase ICEs sionce my r14-650 PR109756 change to
set TREE_VALUE (attr) to error_mark_node for unsupported attributes
for which we've just skipped over balanced tokens for arguments in order
to differentiate that from no arguments.

The problem is that handle_namespace_attrs doesn't go through the normal
attribute handling and just checked attributes by name.
So, if user uses [[visibility (whatever)]] or
[[whatever::visibility (whatever)]] or similarly abi_tag or for deprecated
(which is valid as both [[deprecated ("foo")]] and
[[gnu::deprecated ("foo")]] ) [[whatever::deprecated (whatever)]] on
a namespace, we handle it as if it was a gnu or gnu or standard attribute
even when it is not and can ICE on error_mark_node attributes.

The following patch makes sure we handle it only in the right namespaces
and emit a warning on anything else.

Not sure about backports, the patch changes behavior for say
inline namespace [[foo::abi_tag]] N or
inline namespace [[abi_tag]] N where previously it would use the name
of the namespace as abi tag and now it will ignore it and emit a warning.
One possibility is to just deal with args == error_mark_node and warn
on that attribute only in that case (that is where it would previously ICE).
But perhaps I'm worrying too much and no code in the wild is relying on
non-gnu attributes on namespaces with the same names as the gnu ones
behaving like the gnu ones.

2026-01-24  Jakub Jelinek  <jakub@redhat.com>

	PR c++/123684
	* name-lookup.cc (handle_namespace_attrs): Only handle visibility and
	abi_tag attributes in the gnu namespace and deprecated attribute in
	the standard or gnu namespaces.

	* g++.dg/cpp0x/gen-attrs-90.C: New test.

diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 1b3713dc40e18badf4888c5a024d30a03c3e1fd6..a1f0a0ff38e17fae1744ae3af7968a1394879487 100644 (file)
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -6626,7 +6626,8 @@ handle_namespace_attrs (tree ns, tree attributes)
       tree name = get_attribute_name (d);
       tree args = TREE_VALUE (d);
 
-      if (is_attribute_p ("visibility", name))
+      if (is_attribute_p ("visibility", name)
+         && is_attribute_namespace_p ("gnu", d))
        {
          /* attribute visibility is a property of the syntactic block
             rather than the namespace as a whole, so we don't touch the
@@ -6648,7 +6649,8 @@ handle_namespace_attrs (tree ns, tree attributes)
          push_visibility (TREE_STRING_POINTER (x), 1);
          saw_vis = true;
        }
-      else if (is_attribute_p ("abi_tag", name))
+      else if (is_attribute_p ("abi_tag", name)
+              && is_attribute_namespace_p ("gnu", d))
        {
          if (!DECL_NAME (ns))
            {
@@ -6675,7 +6677,8 @@ handle_namespace_attrs (tree ns, tree attributes)
            DECL_ATTRIBUTES (ns) = tree_cons (name, args,
                                              DECL_ATTRIBUTES (ns));
        }
-      else if (is_attribute_p ("deprecated", name))
+      else if (is_attribute_p ("deprecated", name)
+              && is_attribute_namespace_p ("", d))
        {
          if (!DECL_NAME (ns))
            {

diff --git a/gcc/testsuite/g++.dg/cpp0x/gen-attrs-90.C b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-90.C
new file mode 100644 (file)
index 0000000..28e4885
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/gen-attrs-90.C
@@ -0,0 +1,8 @@
+// PR c++/123684
+// { dg-do compile { target c++11 } }
+
+inline namespace [[foo::abi_tag (1, 2, 3)]] A {}       // { dg-warning "'abi_tag' attribute directive ignored" }
+inline namespace [[foo::visibility (1, 2, 3)]] B {}    // { dg-warning "'visibility' attribute directive ignored" }
+inline namespace [[foo::deprecated (1, 2, 3)]] C {}    // { dg-warning "'deprecated' attribute directive ignored" }
+inline namespace [[abi_tag (1, 2, 3)]] D {}            // { dg-warning "'abi_tag' attribute directive ignored" }
+inline namespace [[visibility (1, 2, 3)]] E {}         // { dg-warning "'visibility' attribute directive ignored" }