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

[Marek Polacek <polacek@redhat.com>]

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