Re: [PATCH] c++: ICE when building builtin operator->* set [PR103455]

[Jason Merrill <jason@redhat.com>]

On 3/25/22 14:09, Patrick Palka wrote:
> When constructing the builtin operator->* candidate set according to
> the available conversion functions for each operand type, we end up
> considering a candidate with C1=T (a TEMPLATE_TYPE_PARM) and C2=F,
> during which we crash from lookup_base because dependent_type_p sees
> a TEMPLATE_TYPE_PARM when processing_template_decl is cleared.
> 
> Sidestepping the question of whether we should be considering a
> dependent conversion function here in the first place (which I'm not
> sure about), it seems futile to check DERIVED_FROM_P for anything other
> than an actual class type, so this patch fixes this ICE by guarding
> the DERIVED_FROM_P test with CLASS_TYPE_P instead of MAYBE_CLASS_TYPE_P.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk and perhaps the release branches?

OK for trunk and branches.

> 	PR c++/103455
> 
> gcc/cp/ChangeLog:
> 
> 	* call.cc (add_builtin_candidate) <case MEMBER_REF>: Check
> 	CLASS_TYPE_P instead of MAYBE_CLASS_TYPE_P.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/overload/builtin6.C: New test.
> ---
>   gcc/cp/call.cc                           |  2 +-
>   gcc/testsuite/g++.dg/overload/builtin6.C | 14 ++++++++++++++
>   2 files changed, 15 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/overload/builtin6.C
> 
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index ec6c5d5baa2..dfe370d685d 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -2821,7 +2821,7 @@ add_builtin_candidate (struct z_candidate **candidates, enum tree_code code,
>   	  tree c1 = TREE_TYPE (type1);
>   	  tree c2 = TYPE_PTRMEM_CLASS_TYPE (type2);
>   
> -	  if (MAYBE_CLASS_TYPE_P (c1) && DERIVED_FROM_P (c2, c1)
> +	  if (CLASS_TYPE_P (c1) && DERIVED_FROM_P (c2, c1)
>   	      && (TYPE_PTRMEMFUNC_P (type2)
>   		  || is_complete (TYPE_PTRMEM_POINTED_TO_TYPE (type2))))
>   	    break;
> diff --git a/gcc/testsuite/g++.dg/overload/builtin6.C b/gcc/testsuite/g++.dg/overload/builtin6.C
> new file mode 100644
> index 00000000000..25e45040094
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/overload/builtin6.C
> @@ -0,0 +1,14 @@
> +// PR c++/103455
> +
> +struct A { };
> +
> +struct B {
> +  operator A*() const;
> +  template<class T> operator T*() const;
> +};
> +
> +typedef void (A::*F)();
> +
> +void foo(B b, F f) {
> +  (b->*f)();
> +}