[PATCH] coroutines: Allow parameter packs in co_await/yield expressions [PR95345]

Nathan Sidwell nathan@acm.org
Mon Jun 1 14:53:55 GMT 2020


On 6/1/20 4:09 AM, Iain Sandoe wrote:
> Hi
> 
> This corrects a pasto, where I copied the constraint on bare
> parameter packs from the co_return to co_yield/await without
> properly reviewing it.
> 
> tested on x86_64,powerpc64-linux, x86_64-darwin
> OK for master?
> OK for 10.2?

ok for both

> thanks
> Iain
> 
> gcc/cp/ChangeLog:
> 
> 	PR c++/95345
> 	* coroutines.cc (finish_co_await_expr): Revise to allow for
> 	parameter packs.
> 	(finish_co_yield_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/95345
> 	* g++.dg/coroutines/pr95345.C: New test.
> ---
>   gcc/cp/coroutines.cc                      | 45 +++++++++++------------
>   gcc/testsuite/g++.dg/coroutines/pr95345.C | 32 ++++++++++++++++
>   2 files changed, 53 insertions(+), 24 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/coroutines/pr95345.C
> 
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index cc685ca73b2..7afa550037c 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -851,19 +851,18 @@ finish_co_await_expr (location_t kw, tree expr)
>     /* The current function has now become a coroutine, if it wasn't already.  */
>     DECL_COROUTINE_P (current_function_decl) = 1;
>   
> -  if (processing_template_decl)
> -    {
> -      current_function_returns_value = 1;
> -
> -      if (check_for_bare_parameter_packs (expr))
> -	return error_mark_node;
> +  /* This function will appear to have no return statement, even if it
> +     is declared to return non-void (most likely).  This is correct - we
> +     synthesize the return for the ramp in the compiler.  So suppress any
> +     extraneous warnings during substitution.  */
> +  TREE_NO_WARNING (current_function_decl) = true;
>   
> -      /* If we don't know the promise type, we can't proceed.  */
> -      tree functype = TREE_TYPE (current_function_decl);
> -      if (dependent_type_p (functype) || type_dependent_expression_p (expr))
> -	return build5_loc (kw, CO_AWAIT_EXPR, unknown_type_node, expr,
> -			   NULL_TREE, NULL_TREE, NULL_TREE, integer_zero_node);
> -    }
> +  /* If we don't know the promise type, we can't proceed, build the
> +     co_await with the expression unchanged.  */
> +  tree functype = TREE_TYPE (current_function_decl);
> +  if (dependent_type_p (functype) || type_dependent_expression_p (expr))
> +    return build5_loc (kw, CO_AWAIT_EXPR, unknown_type_node, expr,
> +		       NULL_TREE, NULL_TREE, NULL_TREE, integer_zero_node);
>   
>     /* We must be able to look up the "await_transform" method in the scope of
>        the promise type, and obtain its return type.  */
> @@ -928,19 +927,17 @@ finish_co_yield_expr (location_t kw, tree expr)
>     /* The current function has now become a coroutine, if it wasn't already.  */
>     DECL_COROUTINE_P (current_function_decl) = 1;
>   
> -  if (processing_template_decl)
> -    {
> -      current_function_returns_value = 1;
> -
> -      if (check_for_bare_parameter_packs (expr))
> -	return error_mark_node;
> +  /* This function will appear to have no return statement, even if it
> +     is declared to return non-void (most likely).  This is correct - we
> +     synthesize the return for the ramp in the compiler.  So suppress any
> +     extraneous warnings during substitution.  */
> +  TREE_NO_WARNING (current_function_decl) = true;
>   
> -      tree functype = TREE_TYPE (current_function_decl);
> -      /* If we don't know the promise type, we can't proceed.  */
> -      if (dependent_type_p (functype) || type_dependent_expression_p (expr))
> -	return build2_loc (kw, CO_YIELD_EXPR, unknown_type_node, expr,
> -			   NULL_TREE);
> -    }
> +  /* If we don't know the promise type, we can't proceed, build the
> +     co_await with the expression unchanged.  */
> +  tree functype = TREE_TYPE (current_function_decl);
> +  if (dependent_type_p (functype) || type_dependent_expression_p (expr))
> +    return build2_loc (kw, CO_YIELD_EXPR, unknown_type_node, expr, NULL_TREE);
>   
>     if (!coro_promise_type_found_p (current_function_decl, kw))
>       /* We must be able to look up the "yield_value" method in the scope of
> diff --git a/gcc/testsuite/g++.dg/coroutines/pr95345.C b/gcc/testsuite/g++.dg/coroutines/pr95345.C
> new file mode 100644
> index 00000000000..90e946d91c2
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/coroutines/pr95345.C
> @@ -0,0 +1,32 @@
> +#if __has_include (<coroutine>)
> +#include <coroutine>
> +using namespace std;
> +#elif defined (__clang__) && __has_include (<experimental/coroutine>)
> +#include <experimental/coroutine>
> +using namespace std::experimental;
> +#endif
> +
> +struct dummy_coro
> +{
> +  using promise_type = dummy_coro;
> +  bool await_ready() { return false; }
> +  void await_suspend(std::coroutine_handle<>) { }
> +  void await_resume() { }
> +  dummy_coro get_return_object() { return {}; }
> +  dummy_coro initial_suspend() { return {}; }
> +  dummy_coro final_suspend() { return {}; }
> +  void return_void() { }
> +  void unhandled_exception() { }
> +};
> +
> +template <int ...I>
> +dummy_coro
> +foo()
> +{
> + ((co_await [](int){ return std::suspend_never{}; }(I)), ...);
> +  co_return;
> +}
> +
> +void bar() {
> +  foo<1>();
> +}
> 


-- 
Nathan Sidwell


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