[PATCH] c++: Fix tsubst ICE with invalid code [PR97993, PR97187]

[Jason Merrill]

On 12/1/20 12:38 PM, Marek Polacek wrote:
> I had a strong sense of deja vu when looking into this, and no wonder,
> since this is almost identical to c++/95728.
> 
> Since r11-423 tsubst_copy_and_build/TREE_LIST uses tsubst_tree_list
> instead of open coding it.  While the latter could return an error
> node wrapped in a TREE_LIST, the former can return a naked error node.
> 
> That broke in tsubst_copy_and_build/NEW_EXPR, because we were accessing
> TREE_VALUE of an error node.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	PR c++/97187
> 	PR c++/97993
> 	* pt.c (tsubst_copy_and_build) <case NEW_EXPR>: Return error_mark_node
> 	if init is erroneous.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/97187
> 	PR c++/97993
> 	* g++.dg/eh/crash2.C: New test.
> 	* g++.dg/template/crash132.C: New test.
> ---
>   gcc/cp/pt.c                              |  2 ++
>   gcc/testsuite/g++.dg/eh/crash2.C         | 20 ++++++++++++++++++++
>   gcc/testsuite/g++.dg/template/crash132.C |  6 ++++++
>   3 files changed, 28 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/eh/crash2.C
>   create mode 100644 gcc/testsuite/g++.dg/template/crash132.C
> 
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 4fb0bc82c31..72d6cc3ad98 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -19829,6 +19829,8 @@ tsubst_copy_and_build (tree t,
>   	   parameter packs are of length zero.  */
>   	if (init == NULL_TREE && TREE_OPERAND (t, 3) == NULL_TREE)
>   	  init_vec = NULL;
> +	else if (init == error_mark_node)
> +	  RETURN (error_mark_node);
>   	else
>   	  {
>   	    init_vec = make_tree_vector ();
> diff --git a/gcc/testsuite/g++.dg/eh/crash2.C b/gcc/testsuite/g++.dg/eh/crash2.C
> new file mode 100644
> index 00000000000..fff8e142fd6
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/eh/crash2.C
> @@ -0,0 +1,20 @@
> +// PR c++/97187
> +// { dg-do compile { target c++14 } }
> +// { dg-options "-fno-exceptions" }
> +
> +auto yp = [] { return 0; };
> +
> +template <class DI>
> +DI
> +zl ()
> +{
> +  auto au = [] () -> DI { return *new auto (true ? yp : throw); }; // { dg-error "exception handling disabled" }
> +
> +  return au ();
> +}
> +
> +auto
> +vd ()
> +{
> +  return zl <decltype (yp)> ();
> +}
> diff --git a/gcc/testsuite/g++.dg/template/crash132.C b/gcc/testsuite/g++.dg/template/crash132.C
> new file mode 100644
> index 00000000000..f6f4863e937
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/crash132.C
> @@ -0,0 +1,6 @@
> +// PR c++/97993
> +// { dg-do compile { target c++14 } }
> +
> +template <class T> T a;
> +template <class T, class A, class=decltype(::new T (A()))> auto foo ();
> +struct S decltype (foo <int, S>); // { dg-error "" }
> 
> base-commit: b46314c78061a5156bac44a317c87d32b00d4295
>