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coroutines: Fix handling of non-class coroutine returns [PR94759] 

From the standard:

The header <coroutine> defines the primary template coroutine_traits
such that if ArgTypes is a parameter pack of types and if the
qualified-id R::promise_type is valid and denotes a type, then
coroutine_traits<R,ArgTypes...> has the following publicly accessible
member:
     using promise_type = typename R::promise_type;

this should not prevent more specialised cases and  the following
code should be accepted, but is currently rejected with:

'error: coroutine return type ‘void’ is not a class'

This is because the check for non-class-ness of the return value was
in the wrong place; it needs to be carried out in a SFINAE context.

The following patch removes the restriction in the traits template
instantiation and allows for the case that the ramp function could
return void.

The <coroutine> header is amended to implement the required
functionality.

gcc/cp/ChangeLog:

2020-04-28  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94759
	* coroutines.cc (coro_promise_type_found_p): Do not
	exclude non-classes here (this needs to be handled in the
	coroutine header).
	(morph_fn_to_coro):  Allow for the case where the coroutine
	returns void.

gcc/testsuite/ChangeLog:

2020-04-28  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94759
	* g++.dg/coroutines/coro-bad-alloc-00-bad-op-new.C: Adjust for
	updated error messages.
	* g++.dg/coroutines/coro-bad-alloc-01-bad-op-del.C: Likewise.
	* g++.dg/coroutines/coro-bad-alloc-02-no-op-new-nt.C: Likewise.
	* g++.dg/coroutines/coro-missing-promise.C: Likewise.
	* g++.dg/coroutines/pr93458-5-bad-coro-type.C: Liekwise.
	* g++.dg/coroutines/torture/co-ret-17-void-ret-coro.C: New test.

libstdc++-v3/ChangeLog:

2020-04-28  Jonathan Wakely  <jwakely@redhat.com>
	    Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94759
	* include/std/coroutine: Implement handing for non-
	class coroutine return types.
This commit is contained in:
Iain Sandoe 2020-04-28 00:27:47 +01:00
parent 5726da6bdc
commit b9c91b7f32
11 changed files with 151 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gcc/cp/ChangeLog
View File

@ -1,3 +1,12 @@
2020-04-28 Iain Sandoe <iain@sandoe.co.uk>
PR c++/94759
* coroutines.cc (coro_promise_type_found_p): Do not
exclude non-classes here (this needs to be handled in the
coroutine header).
(morph_fn_to_coro): Allow for the case where the coroutine
returns void.
2020-04-27 Iain Sandoe <iain@sandoe.co.uk>
PR c++/94701

104
gcc/cp/coroutines.cc
View File

@ -441,18 +441,6 @@ coro_promise_type_found_p (tree fndecl, location_t loc)
{
/* Get the coroutine traits template class instance for the function
signature we have - coroutine_traits <R, ...> */
tree return_type = TREE_TYPE (TREE_TYPE (fndecl));
if (!CLASS_TYPE_P (return_type))
{
/* It makes more sense to show the function header for this, even
though we will have encountered it when processing a keyword.
Only emit the error once, not for every keyword we encounter. */
if (!coro_info->coro_ret_type_error_emitted)
error_at (DECL_SOURCE_LOCATION (fndecl), "coroutine return type"
" %qT is not a class", return_type);
coro_info->coro_ret_type_error_emitted = true;
return false;
}
tree templ_class = instantiate_coro_traits (fndecl, loc);
@ -3518,9 +3506,6 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
if (!coro_function_valid_p (orig))
return false;
/* The ramp function does return a value. */
current_function_returns_value = 1;
/* We can't validly get here with an empty statement list, since there's no
way for the FE to decide it's a coroutine in the absence of any code. */
tree fnbody = pop_stmt_list (DECL_SAVED_TREE (orig));
@ -3593,7 +3578,6 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
1. Types we already know. */
tree fn_return_type = TREE_TYPE (TREE_TYPE (orig));
gcc_assert (!VOID_TYPE_P (fn_return_type));
tree handle_type = get_coroutine_handle_type (orig);
tree promise_type = get_coroutine_promise_type (orig);
@ -3778,7 +3762,6 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
tree ramp_bind = build3 (BIND_EXPR, void_type_node, NULL, NULL, NULL);
add_stmt (ramp_bind);
tree ramp_body = push_stmt_list ();
tree empty_list = build_empty_stmt (fn_start);
tree coro_fp = build_lang_decl (VAR_DECL, get_identifier ("coro.frameptr"),
coro_frame_ptr);
@ -3952,33 +3935,27 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
control to the caller of the coroutine and the return value is
obtained by a call to T::get_return_object_on_allocation_failure(),
where T is the promise type. */
tree cfra_label
= create_named_label_with_ctx (fn_start, "coro.frame.active",
current_scope ());
tree early_ret_list = NULL;
/* init the retval using the user's func. */
r = build2 (INIT_EXPR, TREE_TYPE (DECL_RESULT (orig)), DECL_RESULT (orig),
grooaf);
r = coro_build_cvt_void_expr_stmt (r, fn_start);
append_to_statement_list (r, &early_ret_list);
/* We know it's the correct type. */
r = DECL_RESULT (orig);
r = build_stmt (fn_start, RETURN_EXPR, r);
TREE_NO_WARNING (r) |= 1;
r = maybe_cleanup_point_expr_void (r);
append_to_statement_list (r, &early_ret_list);
tree goto_st = NULL;
r = build1 (GOTO_EXPR, void_type_node, cfra_label);
append_to_statement_list (r, &goto_st);
tree ckk = build1 (CONVERT_EXPR, coro_frame_ptr, integer_zero_node);
tree ckz = build2 (EQ_EXPR, boolean_type_node, coro_fp, ckk);
r = build3 (COND_EXPR, void_type_node, ckz, early_ret_list, empty_list);
add_stmt (r);
cfra_label = build_stmt (fn_start, LABEL_EXPR, cfra_label);
add_stmt (cfra_label);
gcc_checking_assert (same_type_p (fn_return_type, TREE_TYPE (grooaf)));
tree if_stmt = begin_if_stmt ();
tree cond = build1 (CONVERT_EXPR, coro_frame_ptr, integer_zero_node);
cond = build2 (EQ_EXPR, boolean_type_node, coro_fp, cond);
finish_if_stmt_cond (cond, if_stmt);
if (VOID_TYPE_P (fn_return_type))
{
/* Execute the get-return-object-on-alloc-fail call... */
finish_expr_stmt (grooaf);
/* ... but discard the result, since we return void. */
finish_return_stmt (NULL_TREE);
}
else
{
/* Get the fallback return object. */
r = build_cplus_new (fn_return_type, grooaf, tf_warning_or_error);
finish_return_stmt (r);
}
finish_then_clause (if_stmt);
finish_if_stmt (if_stmt);
}
/* deref the frame pointer, to use in member access code. */
@ -4176,17 +4153,25 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
}
tree gro_context_body = push_stmt_list ();
tree gro = build_lang_decl (VAR_DECL, get_identifier ("coro.gro"),
TREE_TYPE (get_ro));
DECL_CONTEXT (gro) = current_scope ();
add_decl_expr (gro);
tree gro_bind_vars = gro;
bool gro_is_void_p = VOID_TYPE_P (TREE_TYPE (get_ro));
tree gro, gro_bind_vars = NULL_TREE;
/* We have to sequence the call to get_return_object before initial
suspend. */
r = build2_loc (fn_start, INIT_EXPR, TREE_TYPE (gro), gro, get_ro);
r = coro_build_cvt_void_expr_stmt (r, fn_start);
add_stmt (r);
if (gro_is_void_p)
finish_expr_stmt (get_ro);
else
{
gro = build_lang_decl (VAR_DECL, get_identifier ("coro.gro"),
TREE_TYPE (get_ro));
DECL_CONTEXT (gro) = current_scope ();
add_decl_expr (gro);
gro_bind_vars = gro;
r = build2_loc (fn_start, INIT_EXPR, TREE_TYPE (gro), gro, get_ro);
r = coro_build_cvt_void_expr_stmt (r, fn_start);
add_stmt (r);
}
/* Initialize the resume_idx_name to 0, meaning "not started". */
tree resume_idx_m
@ -4222,16 +4207,25 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
/* The ramp is done, we just need the return value. */
if (!same_type_p (TREE_TYPE (get_ro), fn_return_type))
{
/* construct the return value with a single GRO param. */
vec<tree, va_gc> *args = make_tree_vector_single (gro);
/* construct the return value with a single GRO param, if it's not
void. */
vec<tree, va_gc> *args = NULL;
vec<tree, va_gc> **arglist = NULL;
if (!gro_is_void_p)
{
args = make_tree_vector_single (gro);
arglist = &args;
}
r = build_special_member_call (NULL_TREE,
complete_ctor_identifier, &args,
complete_ctor_identifier, arglist,
fn_return_type, LOOKUP_NORMAL,
tf_warning_or_error);
r = build_cplus_new (fn_return_type, r, tf_warning_or_error);
}
else
else if (!gro_is_void_p)
r = rvalue (gro); /* The GRO is the return value. */
else
r = NULL_TREE;
finish_return_stmt (r);

13
gcc/testsuite/ChangeLog
View File

@ -1,4 +1,15 @@
2020-04-21 Iain Sandoe <iain@sandoe.co.uk>
2020-04-28 Iain Sandoe <iain@sandoe.co.uk>
PR c++/94759
* g++.dg/coroutines/coro-bad-alloc-00-bad-op-new.C: Adjust for
updated error messages.
* g++.dg/coroutines/coro-bad-alloc-01-bad-op-del.C: Likewise.
* g++.dg/coroutines/coro-bad-alloc-02-no-op-new-nt.C: Likewise.
* g++.dg/coroutines/coro-missing-promise.C: Likewise.
* g++.dg/coroutines/pr93458-5-bad-coro-type.C: Liekwise.
* g++.dg/coroutines/torture/co-ret-17-void-ret-coro.C: New test.
2020-04-27 Iain Sandoe <iain@sandoe.co.uk>
PR c++/94701
* g++.dg/coroutines/torture/local-var-06-structured-binding.C:

2
gcc/testsuite/g++.dg/coroutines/coro-bad-alloc-00-bad-op-new.C
View File

@ -6,7 +6,7 @@
#include "coro1-allocators.h"
struct coro1
f () /* { dg-error {'operator new' is provided by 'std::__n4861::coroutine_traits<coro1>::promise_type' \{aka 'coro1::promise_type'\} but is not usable with the function signature 'coro1 f\(\)'} } */
f () /* { dg-error {'operator new' is provided by 'std::__n4861::__coroutine_traits_impl<coro1, void>::promise_type' \{aka 'coro1::promise_type'\} but is not usable with the function signature 'coro1 f\(\)'} } */
{
co_return;
}

2
gcc/testsuite/g++.dg/coroutines/coro-bad-alloc-01-bad-op-del.C
View File

@ -6,7 +6,7 @@
#include "coro1-allocators.h"
struct coro1
f () /* { dg-error {'operator delete' is provided by 'std::__n4861::coroutine_traits<coro1>::promise_type' \{aka 'coro1::promise_type'\} but is not usable with the function signature 'coro1 f\(\)'} } */
f () /* { dg-error {'operator delete' is provided by 'std::__n4861::__coroutine_traits_impl<coro1, void>::promise_type' \{aka 'coro1::promise_type'\} but is not usable with the function signature 'coro1 f\(\)'} } */
{
co_return;
}

2
gcc/testsuite/g++.dg/coroutines/coro-bad-alloc-02-no-op-new-nt.C
View File

@ -9,7 +9,7 @@
#include "coro1-allocators.h"
struct coro1
f () /* { dg-error {'coro1::promise_type::get_return_object_on_allocation_failure\(\)\(\)' is provided by 'std::__n4861::coroutine_traits<coro1>::promise_type' \{aka 'coro1::promise_type'\} but 'operator new' is not marked 'throw\(\)' or 'noexcept'} } */
f () /* { dg-error {'coro1::promise_type::get_return_object_on_allocation_failure\(\)\(\)' is provided by 'std::__n4861::__coroutine_traits_impl<coro1, void>::promise_type' \{aka 'coro1::promise_type'\} but 'operator new' is not marked 'throw\(\)' or 'noexcept'} } */
{
co_return;
}

2
gcc/testsuite/g++.dg/coroutines/coro-missing-promise.C
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@ -4,8 +4,6 @@
// Diagnose completely missing promise.
// { dg-error {no type named 'promise_type' in 'struct NoPromiseHere'} "" { target *-*-* } 0 }
struct NoPromiseHere {
coro::coroutine_handle<> handle;
NoPromiseHere () : handle (nullptr) {}

4
gcc/testsuite/g++.dg/coroutines/pr93458-5-bad-coro-type.C
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@ -5,8 +5,8 @@
#include "coro.h"
int
bad_coroutine (void) // { dg-error {coroutine return type 'int' is not a class} }
bad_coroutine (void)
{
co_yield 5;
co_yield 5; // { dg-error {unable to find the promise type for this coroutine} }
co_return;
}

57
gcc/testsuite/g++.dg/coroutines/torture/co-ret-17-void-ret-coro.C Normal file
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@ -0,0 +1,57 @@
// { dg-do run }
// Test the ability to specialize the coroutine traits to include
// non-class type coroutine ramp return values.
#include "../coro.h"
template<typename R, typename HandleRef, typename ...T>
struct std::coroutine_traits<R, HandleRef, T...> {
struct promise_type {
promise_type (HandleRef h, T ...args)
{ h = std::coroutine_handle<promise_type>::from_promise (*this);
PRINT ("Created Promise");
}
void get_return_object() {}
auto initial_suspend() {
return std::suspend_always{};
}
auto final_suspend() { return std::suspend_never{}; }
void return_void() {}
void unhandled_exception() {}
};
};
void
my_coro (std::coroutine_handle<>& h)
{
PRINT ("coro1: about to return");
co_return;
}
int main ()
{
std::coroutine_handle<> h;
my_coro (h);
if (h.done())
{
PRINT ("main: apparently was already done...");
abort ();
}
// initial suspend.
h.resume ();
if (!h.done())
{
PRINT ("main: apparently wasn't done...");
abort ();
}
PRINT ("main: returning");
return 0;
}

7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
2020-04-28 Jonathan Wakely <jwakely@redhat.com>
Iain Sandoe <iain@sandoe.co.uk>
PR c++/94759
* include/std/coroutine: Implement handing for non-
class coroutine return types.
2020-04-24 Jonathan Wakely <jwakely@redhat.com>
* include/experimental/executor (service_already_exists): Make default

15
libstdc++-v3/include/std/coroutine
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@ -63,12 +63,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// 17.12.2 coroutine traits
/// [coroutine.traits]
/// [coroutine.traits.primary]
template <typename _Result, typename...>
struct coroutine_traits
/// If _Result::promise_type is valid and denotes a type then the traits
/// have a single publicly accessible member, otherwise they are empty.
template <typename _Result, typename = void>
struct __coroutine_traits_impl {};
template <typename _Result>
struct __coroutine_traits_impl<_Result,
__void_t<typename _Result::promise_type>>
{
using promise_type = typename _Result::promise_type;
using promise_type = typename _Result::promise_type;
};
template <typename _Result, typename...>
struct coroutine_traits : __coroutine_traits_impl<_Result> {};
// 17.12.3 Class template coroutine_handle
/// [coroutine.handle]
template <typename _Promise = void>