[PATCH] c++: fix ICE on invalid attributes [PR96637]

[PATCH] c++: fix ICE on invalid attributes [PR96637]

[Marek Polacek]

This patch fixes crashes with invalid attributes.  Arguably it could
make sense to assert seen_error() too.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk = GCC 13?

	PR c++/96637

gcc/ChangeLog:

	* attribs.cc (decl_attributes): Check error_mark_node.

gcc/cp/ChangeLog:

	* decl2.cc (cp_check_const_attributes): Check error_mark_node.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/error64.C: New test.
---
 gcc/attribs.cc                       | 3 +++
 gcc/cp/decl2.cc                      | 2 ++
 gcc/testsuite/g++.dg/parse/error64.C | 4 ++++
 3 files changed, 9 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/parse/error64.C

diff --git a/gcc/attribs.cc b/gcc/attribs.cc
index b219f878042..ff157dcf81c 100644
--- a/gcc/attribs.cc
+++ b/gcc/attribs.cc
@@ -700,6 +700,9 @@ decl_attributes (tree *node, tree attributes, int flags,
      in the same order as in the source.  */
   for (tree attr = attributes; attr; attr = TREE_CHAIN (attr))
     {
+      if (attr == error_mark_node)
+	continue;
+
       tree ns = get_attribute_namespace (attr);
       tree name = get_attribute_name (attr);
       tree args = TREE_VALUE (attr);
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index d2b29208ed5..c3ff1962a75 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -1537,6 +1537,8 @@ cp_check_const_attributes (tree attributes)
       /* As we implement alignas using gnu::aligned attribute and
 	 alignas argument is a constant expression, force manifestly
 	 constant evaluation of aligned attribute argument.  */
+      if (attr == error_mark_node)
+	continue;
       bool manifestly_const_eval
 	= is_attribute_p ("aligned", get_attribute_name (attr));
       for (arg = TREE_VALUE (attr); arg && TREE_CODE (arg) == TREE_LIST;
diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
new file mode 100644
index 00000000000..87848a58c27
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/error64.C
@@ -0,0 +1,4 @@
+// PR c++/96637
+// { dg-do compile }
+
+void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }

base-commit: 9ae8b993cd362e8aea4f65580aaf1453120207f2
-- 
2.35.1

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Marek Polacek]

Ping.

On Fri, Apr 29, 2022 at 10:12:33AM -0400, Marek Polacek via Gcc-patches wrote:
> This patch fixes crashes with invalid attributes.  Arguably it could
> make sense to assert seen_error() too.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk = GCC 13?
> 
> 	PR c++/96637
> 
> gcc/ChangeLog:
> 
> 	* attribs.cc (decl_attributes): Check error_mark_node.
> 
> gcc/cp/ChangeLog:
> 
> 	* decl2.cc (cp_check_const_attributes): Check error_mark_node.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/parse/error64.C: New test.
> ---
>  gcc/attribs.cc                       | 3 +++
>  gcc/cp/decl2.cc                      | 2 ++
>  gcc/testsuite/g++.dg/parse/error64.C | 4 ++++
>  3 files changed, 9 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/parse/error64.C
> 
> diff --git a/gcc/attribs.cc b/gcc/attribs.cc
> index b219f878042..ff157dcf81c 100644
> --- a/gcc/attribs.cc
> +++ b/gcc/attribs.cc
> @@ -700,6 +700,9 @@ decl_attributes (tree *node, tree attributes, int flags,
>       in the same order as in the source.  */
>    for (tree attr = attributes; attr; attr = TREE_CHAIN (attr))
>      {
> +      if (attr == error_mark_node)
> +	continue;
> +
>        tree ns = get_attribute_namespace (attr);
>        tree name = get_attribute_name (attr);
>        tree args = TREE_VALUE (attr);
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index d2b29208ed5..c3ff1962a75 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -1537,6 +1537,8 @@ cp_check_const_attributes (tree attributes)
>        /* As we implement alignas using gnu::aligned attribute and
>  	 alignas argument is a constant expression, force manifestly
>  	 constant evaluation of aligned attribute argument.  */
> +      if (attr == error_mark_node)
> +	continue;
>        bool manifestly_const_eval
>  	= is_attribute_p ("aligned", get_attribute_name (attr));
>        for (arg = TREE_VALUE (attr); arg && TREE_CODE (arg) == TREE_LIST;
> diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
> new file mode 100644
> index 00000000000..87848a58c27
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/error64.C
> @@ -0,0 +1,4 @@
> +// PR c++/96637
> +// { dg-do compile }
> +
> +void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }
> 
> base-commit: 9ae8b993cd362e8aea4f65580aaf1453120207f2
> -- 
> 2.35.1
> 

Marek

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Prathamesh Kulkarni]

On Fri, 29 Apr 2022 at 19:44, Marek Polacek via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch fixes crashes with invalid attributes.  Arguably it could
> make sense to assert seen_error() too.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk = GCC 13?
>
>         PR c++/96637
>
> gcc/ChangeLog:
>
>         * attribs.cc (decl_attributes): Check error_mark_node.
>
> gcc/cp/ChangeLog:
>
>         * decl2.cc (cp_check_const_attributes): Check error_mark_node.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/parse/error64.C: New test.
> ---
>  gcc/attribs.cc                       | 3 +++
>  gcc/cp/decl2.cc                      | 2 ++
>  gcc/testsuite/g++.dg/parse/error64.C | 4 ++++
>  3 files changed, 9 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/parse/error64.C
>
> diff --git a/gcc/attribs.cc b/gcc/attribs.cc
> index b219f878042..ff157dcf81c 100644
> --- a/gcc/attribs.cc
> +++ b/gcc/attribs.cc
> @@ -700,6 +700,9 @@ decl_attributes (tree *node, tree attributes, int flags,
>       in the same order as in the source.  */
>    for (tree attr = attributes; attr; attr = TREE_CHAIN (attr))
>      {
> +      if (attr == error_mark_node)
> +       continue;
Not a comment on the patch specifically, but just wondering if it'd be
better to use error_operand_p,
than testing against error_mark_node explicitly ?

Thanks,
Prathamesh
> +
>        tree ns = get_attribute_namespace (attr);
>        tree name = get_attribute_name (attr);
>        tree args = TREE_VALUE (attr);
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index d2b29208ed5..c3ff1962a75 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -1537,6 +1537,8 @@ cp_check_const_attributes (tree attributes)
>        /* As we implement alignas using gnu::aligned attribute and
>          alignas argument is a constant expression, force manifestly
>          constant evaluation of aligned attribute argument.  */
> +      if (attr == error_mark_node)
> +       continue;
>        bool manifestly_const_eval
>         = is_attribute_p ("aligned", get_attribute_name (attr));
>        for (arg = TREE_VALUE (attr); arg && TREE_CODE (arg) == TREE_LIST;
> diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
> new file mode 100644
> index 00000000000..87848a58c27
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/error64.C
> @@ -0,0 +1,4 @@
> +// PR c++/96637
> +// { dg-do compile }
> +
> +void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }
>
> base-commit: 9ae8b993cd362e8aea4f65580aaf1453120207f2
> --
> 2.35.1
>

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Jason Merrill]

On 4/29/22 10:12, Marek Polacek wrote:
> This patch fixes crashes with invalid attributes.  Arguably it could
> make sense to assert seen_error() too.

So in this testcase we have TREE_CHAIN of a TREE_LIST pointing to 
error_mark_node?  Can we avoid that?

> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk = GCC 13?
> 
> 	PR c++/96637
> 
> gcc/ChangeLog:
> 
> 	* attribs.cc (decl_attributes): Check error_mark_node.
> 
> gcc/cp/ChangeLog:
> 
> 	* decl2.cc (cp_check_const_attributes): Check error_mark_node.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/parse/error64.C: New test.
> ---
>   gcc/attribs.cc                       | 3 +++
>   gcc/cp/decl2.cc                      | 2 ++
>   gcc/testsuite/g++.dg/parse/error64.C | 4 ++++
>   3 files changed, 9 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/parse/error64.C
> 
> diff --git a/gcc/attribs.cc b/gcc/attribs.cc
> index b219f878042..ff157dcf81c 100644
> --- a/gcc/attribs.cc
> +++ b/gcc/attribs.cc
> @@ -700,6 +700,9 @@ decl_attributes (tree *node, tree attributes, int flags,
>        in the same order as in the source.  */
>     for (tree attr = attributes; attr; attr = TREE_CHAIN (attr))
>       {
> +      if (attr == error_mark_node)
> +	continue;
> +
>         tree ns = get_attribute_namespace (attr);
>         tree name = get_attribute_name (attr);
>         tree args = TREE_VALUE (attr);
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index d2b29208ed5..c3ff1962a75 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -1537,6 +1537,8 @@ cp_check_const_attributes (tree attributes)
>         /* As we implement alignas using gnu::aligned attribute and
>   	 alignas argument is a constant expression, force manifestly
>   	 constant evaluation of aligned attribute argument.  */
> +      if (attr == error_mark_node)
> +	continue;
>         bool manifestly_const_eval
>   	= is_attribute_p ("aligned", get_attribute_name (attr));
>         for (arg = TREE_VALUE (attr); arg && TREE_CODE (arg) == TREE_LIST;
> diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
> new file mode 100644
> index 00000000000..87848a58c27
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/error64.C
> @@ -0,0 +1,4 @@
> +// PR c++/96637
> +// { dg-do compile }
> +
> +void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }
> 
> base-commit: 9ae8b993cd362e8aea4f65580aaf1453120207f2

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Marek Polacek]

On Tue, May 24, 2022 at 05:29:56PM +0530, Prathamesh Kulkarni wrote:
> On Fri, 29 Apr 2022 at 19:44, Marek Polacek via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > This patch fixes crashes with invalid attributes.  Arguably it could
> > make sense to assert seen_error() too.
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk = GCC 13?
> >
> >         PR c++/96637
> >
> > gcc/ChangeLog:
> >
> >         * attribs.cc (decl_attributes): Check error_mark_node.
> >
> > gcc/cp/ChangeLog:
> >
> >         * decl2.cc (cp_check_const_attributes): Check error_mark_node.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * g++.dg/parse/error64.C: New test.
> > ---
> >  gcc/attribs.cc                       | 3 +++
> >  gcc/cp/decl2.cc                      | 2 ++
> >  gcc/testsuite/g++.dg/parse/error64.C | 4 ++++
> >  3 files changed, 9 insertions(+)
> >  create mode 100644 gcc/testsuite/g++.dg/parse/error64.C
> >
> > diff --git a/gcc/attribs.cc b/gcc/attribs.cc
> > index b219f878042..ff157dcf81c 100644
> > --- a/gcc/attribs.cc
> > +++ b/gcc/attribs.cc
> > @@ -700,6 +700,9 @@ decl_attributes (tree *node, tree attributes, int flags,
> >       in the same order as in the source.  */
> >    for (tree attr = attributes; attr; attr = TREE_CHAIN (attr))
> >      {
> > +      if (attr == error_mark_node)
> > +       continue;
> Not a comment on the patch specifically, but just wondering if it'd be
> better to use error_operand_p,
> than testing against error_mark_node explicitly ?

Not here, I don't think; it tests more than is needed here.

Marek

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Marek Polacek]

On Tue, May 24, 2022 at 08:22:22AM -0400, Jason Merrill wrote:
> On 4/29/22 10:12, Marek Polacek wrote:
> > This patch fixes crashes with invalid attributes.  Arguably it could
> > make sense to assert seen_error() too.
> 
> So in this testcase we have TREE_CHAIN of a TREE_LIST pointing to
> error_mark_node?  Can we avoid that?

Yes and yes.  Sorry, my previous fix was lousy.  This one is better:

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
When chaining attributes, attr_chainon should be used rather than plain
chainon, so that we don't end up with a TREE_LIST where one of the elements
is error_mark_node, which causes problems.  parser.cc has already been
fixed to use attr_chainon, but decl.cc has not.  Until now.

	PR c++/96637

gcc/cp/ChangeLog:

	* cp-tree.h (attr_chainon): Declare.
	* decl.cc (start_decl): Use attr_chainon.
	(grokdeclarator): Likewise.
	* parser.cc (cp_parser_statement): No longer static.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/error64.C: New test.
---
 gcc/cp/cp-tree.h                     |  1 +
 gcc/cp/decl.cc                       | 19 ++++++++++---------
 gcc/cp/parser.cc                     |  2 +-
 gcc/testsuite/g++.dg/parse/error64.C |  4 ++++
 4 files changed, 16 insertions(+), 10 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/parse/error64.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index ba986e892b6..d77fd1eb8a9 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7235,6 +7235,7 @@ extern void inject_this_parameter (tree, cp_cv_quals);
 extern location_t defparse_location (tree);
 extern void maybe_show_extern_c_location (void);
 extern bool literal_integer_zerop (const_tree);
+extern tree attr_chainon (tree, tree);
 
 /* in pt.cc */
 extern tree canonical_type_parameter		(tree);
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 381259cb9cf..b1ea838ce8b 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -5557,7 +5557,7 @@ start_decl (const cp_declarator *declarator,
   *pushed_scope_p = NULL_TREE;
 
   if (prefix_attributes != error_mark_node)
-    attributes = chainon (attributes, prefix_attributes);
+    attributes = attr_chainon (attributes, prefix_attributes);
 
   decl = grokdeclarator (declarator, declspecs, NORMAL, initialized,
 			 &attributes);
@@ -12728,9 +12728,10 @@ grokdeclarator (const cp_declarator *declarator,
 	       as a whole.  */
 	    late_attrs = splice_template_attributes (&attrs, type);
 	  returned_attrs = decl_attributes (&type,
-					    chainon (returned_attrs, attrs),
+					    attr_chainon (returned_attrs,
+							  attrs),
 					    attr_flags);
-	  returned_attrs = chainon (late_attrs, returned_attrs);
+	  returned_attrs = attr_chainon (late_attrs, returned_attrs);
 	}
 
       inner_declarator = declarator->declarator;
@@ -12781,8 +12782,8 @@ grokdeclarator (const cp_declarator *declarator,
 
 	       The optional attribute-specifier-seq appertains to the
 	       array.  */
-	    returned_attrs = chainon (returned_attrs,
-				      declarator->std_attributes);
+	    returned_attrs = attr_chainon (returned_attrs,
+					   declarator->std_attributes);
 	  break;
 
 	case cdk_function:
@@ -13122,9 +13123,9 @@ grokdeclarator (const cp_declarator *declarator,
 		/* transaction_safe applies to the type, but
 		   transaction_safe_dynamic applies to the function.  */
 		if (is_attribute_p ("transaction_safe", tx_qual))
-		  attrs = chainon (attrs, att);
+		  attrs = attr_chainon (attrs, att);
 		else
-		  returned_attrs = chainon (returned_attrs, att);
+		  returned_attrs = attr_chainon (returned_attrs, att);
 	      }
 	    if (attrs)
 	      /* [dcl.fct]/2:
@@ -13438,7 +13439,7 @@ grokdeclarator (const cp_declarator *declarator,
   if (returned_attrs)
     {
       if (attrlist)
-	*attrlist = chainon (returned_attrs, *attrlist);
+	*attrlist = attr_chainon (returned_attrs, *attrlist);
       else
 	attrlist = &returned_attrs;
     }
@@ -13451,7 +13452,7 @@ grokdeclarator (const cp_declarator *declarator,
       /* [dcl.meaning]/1: The optional attribute-specifier-seq following
 	 a declarator-id appertains to the entity that is declared.  */
       if (declarator->std_attributes != error_mark_node)
-	*attrlist = chainon (*attrlist, declarator->std_attributes);
+	*attrlist = attr_chainon (*attrlist, declarator->std_attributes);
       else
 	/* We should have already diagnosed the issue (c++/78344).  */
 	gcc_assert (seen_error ());
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 868b8610d60..62aaccda23d 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -12557,7 +12557,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
 
 /* Append ATTR to attribute list ATTRS.  */
 
-static tree
+tree
 attr_chainon (tree attrs, tree attr)
 {
   if (attrs == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
new file mode 100644
index 00000000000..87848a58c27
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/error64.C
@@ -0,0 +1,4 @@
+// PR c++/96637
+// { dg-do compile }
+
+void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }

base-commit: 850a9ce8bcca59c7efabcdeeca14c5bd905e8363
-- 
2.36.1

Re: [PATCH] c++: fix ICE on invalid attributes [PR96637]

[Jason Merrill]

On 5/25/22 14:49, Marek Polacek wrote:
> On Tue, May 24, 2022 at 08:22:22AM -0400, Jason Merrill wrote:
>> On 4/29/22 10:12, Marek Polacek wrote:
>>> This patch fixes crashes with invalid attributes.  Arguably it could
>>> make sense to assert seen_error() too.
>>
>> So in this testcase we have TREE_CHAIN of a TREE_LIST pointing to
>> error_mark_node?  Can we avoid that?
> 
> Yes and yes.  Sorry, my previous fix was lousy.  This one is better:
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK, thanks.

> -- >8 --
> When chaining attributes, attr_chainon should be used rather than plain
> chainon, so that we don't end up with a TREE_LIST where one of the elements
> is error_mark_node, which causes problems.  parser.cc has already been
> fixed to use attr_chainon, but decl.cc has not.  Until now.
> 
> 	PR c++/96637
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-tree.h (attr_chainon): Declare.
> 	* decl.cc (start_decl): Use attr_chainon.
> 	(grokdeclarator): Likewise.
> 	* parser.cc (cp_parser_statement): No longer static.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/parse/error64.C: New test.
> ---
>   gcc/cp/cp-tree.h                     |  1 +
>   gcc/cp/decl.cc                       | 19 ++++++++++---------
>   gcc/cp/parser.cc                     |  2 +-
>   gcc/testsuite/g++.dg/parse/error64.C |  4 ++++
>   4 files changed, 16 insertions(+), 10 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/parse/error64.C
> 
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index ba986e892b6..d77fd1eb8a9 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7235,6 +7235,7 @@ extern void inject_this_parameter (tree, cp_cv_quals);
>   extern location_t defparse_location (tree);
>   extern void maybe_show_extern_c_location (void);
>   extern bool literal_integer_zerop (const_tree);
> +extern tree attr_chainon (tree, tree);
>   
>   /* in pt.cc */
>   extern tree canonical_type_parameter		(tree);
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 381259cb9cf..b1ea838ce8b 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -5557,7 +5557,7 @@ start_decl (const cp_declarator *declarator,
>     *pushed_scope_p = NULL_TREE;
>   
>     if (prefix_attributes != error_mark_node)
> -    attributes = chainon (attributes, prefix_attributes);
> +    attributes = attr_chainon (attributes, prefix_attributes);
>   
>     decl = grokdeclarator (declarator, declspecs, NORMAL, initialized,
>   			 &attributes);
> @@ -12728,9 +12728,10 @@ grokdeclarator (const cp_declarator *declarator,
>   	       as a whole.  */
>   	    late_attrs = splice_template_attributes (&attrs, type);
>   	  returned_attrs = decl_attributes (&type,
> -					    chainon (returned_attrs, attrs),
> +					    attr_chainon (returned_attrs,
> +							  attrs),
>   					    attr_flags);
> -	  returned_attrs = chainon (late_attrs, returned_attrs);
> +	  returned_attrs = attr_chainon (late_attrs, returned_attrs);
>   	}
>   
>         inner_declarator = declarator->declarator;
> @@ -12781,8 +12782,8 @@ grokdeclarator (const cp_declarator *declarator,
>   
>   	       The optional attribute-specifier-seq appertains to the
>   	       array.  */
> -	    returned_attrs = chainon (returned_attrs,
> -				      declarator->std_attributes);
> +	    returned_attrs = attr_chainon (returned_attrs,
> +					   declarator->std_attributes);
>   	  break;
>   
>   	case cdk_function:
> @@ -13122,9 +13123,9 @@ grokdeclarator (const cp_declarator *declarator,
>   		/* transaction_safe applies to the type, but
>   		   transaction_safe_dynamic applies to the function.  */
>   		if (is_attribute_p ("transaction_safe", tx_qual))
> -		  attrs = chainon (attrs, att);
> +		  attrs = attr_chainon (attrs, att);
>   		else
> -		  returned_attrs = chainon (returned_attrs, att);
> +		  returned_attrs = attr_chainon (returned_attrs, att);
>   	      }
>   	    if (attrs)
>   	      /* [dcl.fct]/2:
> @@ -13438,7 +13439,7 @@ grokdeclarator (const cp_declarator *declarator,
>     if (returned_attrs)
>       {
>         if (attrlist)
> -	*attrlist = chainon (returned_attrs, *attrlist);
> +	*attrlist = attr_chainon (returned_attrs, *attrlist);
>         else
>   	attrlist = &returned_attrs;
>       }
> @@ -13451,7 +13452,7 @@ grokdeclarator (const cp_declarator *declarator,
>         /* [dcl.meaning]/1: The optional attribute-specifier-seq following
>   	 a declarator-id appertains to the entity that is declared.  */
>         if (declarator->std_attributes != error_mark_node)
> -	*attrlist = chainon (*attrlist, declarator->std_attributes);
> +	*attrlist = attr_chainon (*attrlist, declarator->std_attributes);
>         else
>   	/* We should have already diagnosed the issue (c++/78344).  */
>   	gcc_assert (seen_error ());
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 868b8610d60..62aaccda23d 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -12557,7 +12557,7 @@ cp_parser_statement (cp_parser* parser, tree in_statement_expr,
>   
>   /* Append ATTR to attribute list ATTRS.  */
>   
> -static tree
> +tree
>   attr_chainon (tree attrs, tree attr)
>   {
>     if (attrs == error_mark_node)
> diff --git a/gcc/testsuite/g++.dg/parse/error64.C b/gcc/testsuite/g++.dg/parse/error64.C
> new file mode 100644
> index 00000000000..87848a58c27
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/error64.C
> @@ -0,0 +1,4 @@
> +// PR c++/96637
> +// { dg-do compile }
> +
> +void foo(int[] alignas[1] alignas(1)){} // { dg-error "" }
> 
> base-commit: 850a9ce8bcca59c7efabcdeeca14c5bd905e8363