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

[Jason Merrill <jason@redhat.com>]

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