Hi,

There was a formatting error, corrected in the updated attached patch 
:-/

On 5 Jun 2024, at 10:13, Simon Martin wrote:

> We currently ICE upon the following because we don't properly handle 
> local
> functions with an error_mark_node as DECL_LOCAL_DECL_ALIAS in 
> duplicate_decls.
>
> === cut here ===
> void f (void) {
>   virtual int f (void) const;
>   virtual int f (void);
> }
> === cut here ===
>
> This patch fixes this by checking for error_mark_node.
>
> Successfully tested on x86_64-pc-linux-gnu.
>
> 	PR c++/107575
>
> gcc/cp/ChangeLog:
>
> 	* decl.cc (duplicate_decls): Check for error_mark_node
> 	DECL_LOCAL_DECL_ALIAS.
>
> gcc/testsuite/ChangeLog:
>
> 	* g++.dg/parse/crash74.C: New test.
>
> ---
>  gcc/cp/decl.cc                       | 11 +++++++----
>  gcc/testsuite/g++.dg/parse/crash74.C | 11 +++++++++++
>  2 files changed, 18 insertions(+), 4 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/parse/crash74.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index d481e1ec074..2ae46143d70 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -2792,10 +2792,13 @@ duplicate_decls (tree newdecl, tree olddecl, 
> bool hiding, bool was_hidden)
>  	  retrofit_lang_decl (newdecl);
>  	  tree alias = DECL_LOCAL_DECL_ALIAS (newdecl)
>  	    = DECL_LOCAL_DECL_ALIAS (olddecl);
> -	  DECL_ATTRIBUTES (alias)
> -	    = (*targetm.merge_decl_attributes) (alias, newdecl);
> -	  if (TREE_CODE (newdecl) == FUNCTION_DECL)
> -	    merge_attribute_bits (newdecl, alias);
> +	  if (alias != error_mark_node)
> +	    {
> +	      DECL_ATTRIBUTES (alias) =
The = sign should have been on the next line; this is the case in the 
updated patch.

> +		(*targetm.merge_decl_attributes) (alias, newdecl);
> +	      if (TREE_CODE (newdecl) == FUNCTION_DECL)
> +		merge_attribute_bits (newdecl, alias);
> +	    }
>  	}
>      }
>
> diff --git a/gcc/testsuite/g++.dg/parse/crash74.C 
> b/gcc/testsuite/g++.dg/parse/crash74.C
> new file mode 100644
> index 00000000000..a7ba5094be6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/crash74.C
> @@ -0,0 +1,11 @@
> +// PR c++/107575
> +
> +void f (void) {
> +  virtual int f (void) const; // { dg-line line_4 }
> +  virtual int f (void); // { dg-line line_5 }
> +}
> +
> +// { dg-error "outside class declaration" {} { target *-*-* } line_4 
> }
> +// { dg-error "cannot have cv-qualifier" {} { target *-*-* } line_4 }
> +// { dg-error "ambiguating new declaration of" {} { target *-*-* } 
> line_4 }
> +// { dg-error "outside class declaration" {} { target *-*-* } line_5 
> }
> -- 
> 2.44.0