[PATCH/RFC] How to fix PR95440

[Jason Merrill]

On 6/10/20 4:43 PM, Iain Sandoe wrote:
> Hi Jason,
> 
> Jason Merrill <jason@redhat.com> wrote:
> 
>> On Tue, Jun 9, 2020 at 5:04 AM Iain Sandoe <iain@sandoe.co.uk> wrote:
>>
> 
>>          /* Don't bother reversing an operator with two identical parameters.  */
>> -      else if (args->length () == 2 && (flags & LOOKUP_REVERSED))
>> +      else if (args && args->length () == 2 && (flags & LOOKUP_REVERSED))
>>
>> The usual pattern is to use vec_safe_length here.  Similarly, in build_new_method_call_1 I think
>>
>> !user_args->is_empty()
>>
>> should be
>>
>> vec_safe_is_empty (user_args)
>>
>> Those changes are OK.
> 
> Thanks,
> 
> What I applied (after regtest on x86_64-linux/darwin and powerpc64-linux) is below.
> 
> Given that this fixes an IDE-on-valid filed against 10.1, I’d like to backport it for 10.2,
> is that OK?

Yes.

> thanks
> Iain
> 
> coroutines: Make call argument handling more robust [PR95440]
> 
> build_new_method_call is supposed to be able to handle a null
> arguments list pointer (when the method has no parms).  There
> were a couple of places where uses of the argument list pointer
> were not defended against NULL.
> 
> gcc/cp/ChangeLog:
> 
> 	PR c++/95440
> 	* call.c (add_candidates): Use vec_safe_length() for
> 	testing the arguments list.
> 	(build_new_method_call_1): Use vec_safe_is_empty() when
> 	checking for an empty args list.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/95440
> 	* g++.dg/coroutines/pr95440.C: New test.
> ---
>   gcc/cp/call.c                             |  4 +--
>   gcc/testsuite/g++.dg/coroutines/pr95440.C | 39 +++++++++++++++++++++++
>   2 files changed, 41 insertions(+), 2 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/coroutines/pr95440.C
> 
> diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> index 3c97b9846e2..b99959f76f9 100644
> --- a/gcc/cp/call.c
> +++ b/gcc/cp/call.c
> @@ -5862,7 +5862,7 @@ add_candidates (tree fns, tree first_arg, const vec<tree, va_gc> *args,
>   	}
>   
>         /* Don't bother reversing an operator with two identical parameters.  */
> -      else if (args->length () == 2 && (flags & LOOKUP_REVERSED))
> +      else if (vec_safe_length (args) == 2 && (flags & LOOKUP_REVERSED))
>   	{
>   	  tree parmlist = TYPE_ARG_TYPES (TREE_TYPE (fn));
>   	  if (same_type_p (TREE_VALUE (parmlist),
> @@ -10263,7 +10263,7 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
>   	  && !(flags & LOOKUP_ONLYCONVERTING)
>   	  && cxx_dialect >= cxx20
>   	  && CP_AGGREGATE_TYPE_P (basetype)
> -	  && !user_args->is_empty ())
> +	  && !vec_safe_is_empty (user_args))
>   	{
>   	  /* Create a CONSTRUCTOR from ARGS, e.g. {1, 2} from <1, 2>.  */
>   	  tree list = build_tree_list_vec (user_args);
> diff --git a/gcc/testsuite/g++.dg/coroutines/pr95440.C b/gcc/testsuite/g++.dg/coroutines/pr95440.C
> new file mode 100644
> index 00000000000..8542880d1ab
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/coroutines/pr95440.C
> @@ -0,0 +1,39 @@
> +#if __has_include(<coroutine>)
> +#include <coroutine>
> +#else
> +#include <experimental/coroutine>
> +namespace std { using namespace experimental; }
> +#endif
> +#if 0
> +struct suspend_n {
> +  const int x;
> +  constexpr suspend_n (int x) : x (x) {}
> +  constexpr static bool await_ready() { return false; }
> +  constexpr static void await_suspend(std::coroutine_handle<>) {}
> +  constexpr static void await_resume() {}
> +};
> +#endif
> +struct task
> +{
> +  struct promise_type
> +  {
> +    auto get_return_object() const { return task{}; }
> +#if 0
> +//    static constexpr suspend_n initial_suspend()  { return {2}; }
> +#endif
> +    static constexpr std::suspend_always initial_suspend()  { return {}; }
> +    static constexpr std::suspend_never final_suspend() { return {}; }
> +    static constexpr void return_void() {}
> +    static constexpr void unhandled_exception() {}
> +  };
> +};
> +
> +task
> +test_task ()
> +{
> +  co_await std::suspend_always{};
> +}
> +
> +auto t = test_task();
> +
> +int main() {}
>