[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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