Re: [PATCH] c++: ICE when xobj is not the first parm [PR113389]

[Jason Merrill <jason@redhat.com>]

On 1/17/24 20:17, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> -- >8 --
> In grokdeclarator/cdk_function the comment says that the find_xobj_parm
> lambda clears TREE_PURPOSE so that we can correctly detect an xobj that
> is not the first parameter.  That's all good, but we should also clear
> the TREE_PURPOSE once we've given the error, otherwise we crash later in
> check_default_argument because the 'this' TREE_PURPOSE lacks a type.
> 
> 	PR c++/113389
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (grokdeclarator) <case cdk_function>: Set TREE_PURPOSE to
> 	NULL_TREE when emitting an error.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp23/explicit-obj-diagnostics10.C: New test.
> ---
>   gcc/cp/decl.cc                                          | 1 +
>   gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics10.C | 8 ++++++++
>   2 files changed, 9 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics10.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 322e48dee2e..3e41fd4fa31 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -13391,6 +13391,7 @@ grokdeclarator (const cp_declarator *declarator,
>   		  if (TREE_PURPOSE (parm) != this_identifier)
>   		    continue;
>   		  bad_xobj_parm_encountered = true;
> +		  TREE_PURPOSE (parm) = NULL_TREE;
>   		  gcc_rich_location bad_xobj_parm
>   		    (DECL_SOURCE_LOCATION (TREE_VALUE (parm)));
>   		  error_at (&bad_xobj_parm,
> diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics10.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics10.C
> new file mode 100644
> index 00000000000..354823db166
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics10.C
> @@ -0,0 +1,8 @@
> +// PR c++/113389
> +// { dg-do compile { target c++23 } }
> +
> +struct A {
> +  void foo(A, this A);	// { dg-error "only the first parameter" }
> +  void qux(A, this A,	// { dg-error "only the first parameter" }
> +	   this A);	// { dg-error "only the first parameter" }
> +};
> 
> base-commit: 4a8430c8c3abb1c2c14274105b3a621100f251a2