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c++: don't call 'rvalue' in coroutines code

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A change to check glvalue_p rather than specifically for TARGET_EXPR
revealed issues with the coroutines code's use of the 'rvalue' function,
which shouldn't be used on class glvalues, so I've removed those calls.

In build_co_await I just dropped them, because I don't see anything in the
co_await specification that indicates that we would want to move from an
lvalue result of operator co_await.  And simplified that code while I was
touching it; cp_build_modify_expr (...INIT_EXPR...) will call the
constructor.

In morph_fn_to_coro I changed the handling of the rvalue reference coroutine
frame field to use move, to treat the rval ref as an xvalue.  I used
forward_parm to pass the function parms to the constructor for the field.
And I simplified the return handling so we get the desired rvalue semantics
from the normal implicit move on return.

I question default-initializing the non-void return value of the function if
get_return_object returns void; I'm not messing with it here, but I've filed
PR100476 about it.

gcc/cp/ChangeLog:

	* coroutines.cc (build_co_await): Don't call 'rvalue'.
	(flatten_await_stmt): Simplify initialization.
	(morph_fn_to_coro): Change 'rvalue' to 'move'.  Simplify.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C:
	Adjust diagnostic.
This commit is contained in:
Jason Merrill 2021-05-04 21:33:36 -04:00
parent 601191b2a4
commit 14ed21f874
2 changed files with 31 additions and 88 deletions
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117
gcc/cp/coroutines.cc
View file

@ -950,18 +950,11 @@ build_co_await (location_t loc, tree a, suspend_point_kind suspend_kind)
e_proxy = o;
o = NULL_TREE; /* The var is already present. */
}
else if (type_build_ctor_call (o_type))
{
e_proxy = get_awaitable_var (suspend_kind, o_type);
releasing_vec arg (make_tree_vector_single (rvalue (o)));
o = build_special_member_call (e_proxy, complete_ctor_identifier,
&arg, o_type, LOOKUP_NORMAL,
tf_warning_or_error);
}
else
{
e_proxy = get_awaitable_var (suspend_kind, o_type);
o = build2 (INIT_EXPR, o_type, e_proxy, rvalue (o));
o = cp_build_modify_expr (loc, e_proxy, INIT_EXPR, o,
tf_warning_or_error);
}
/* I suppose we could check that this is contextually convertible to bool. */
@ -2989,15 +2982,8 @@ flatten_await_stmt (var_nest_node *n, hash_set<tree> *promoted,
gcc_checking_assert (!already_present);
tree inner = TREE_OPERAND (init, 1);
gcc_checking_assert (TREE_CODE (inner) != COND_EXPR);
if (type_build_ctor_call (var_type))
{
releasing_vec p_in (make_tree_vector_single (init));
init = build_special_member_call (var, complete_ctor_identifier,
&p_in, var_type, LOOKUP_NORMAL,
tf_warning_or_error);
}
else
init = build2 (INIT_EXPR, var_type, var, init);
init = cp_build_modify_expr (input_location, var, INIT_EXPR, init,
tf_warning_or_error);
/* Simplify for the case that we have an init containing the temp
alone. */
if (t == n->init && n->var == NULL_TREE)
@ -4862,43 +4848,19 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
vec_safe_push (promise_args, this_ref);
}
else if (parm.rv_ref)
vec_safe_push (promise_args, rvalue(fld_idx));
vec_safe_push (promise_args, move (fld_idx));
else
vec_safe_push (promise_args, fld_idx);
if (parm.rv_ref || parm.pt_ref)
/* Initialise the frame reference field directly. */
r = build_modify_expr (fn_start, TREE_OPERAND (fld_idx, 0),
parm.frame_type, INIT_EXPR,
DECL_SOURCE_LOCATION (arg), arg,
DECL_ARG_TYPE (arg));
else if (type_build_ctor_call (parm.frame_type))
{
vec<tree, va_gc> *p_in;
if (CLASS_TYPE_P (parm.frame_type)
&& classtype_has_non_deleted_move_ctor (parm.frame_type))
p_in = make_tree_vector_single (move (arg));
else if (lvalue_p (arg))
p_in = make_tree_vector_single (rvalue (arg));
else
p_in = make_tree_vector_single (arg);
/* Construct in place or move as relevant. */
r = build_special_member_call (fld_idx, complete_ctor_identifier,
&p_in, parm.frame_type,
LOOKUP_NORMAL,
tf_warning_or_error);
release_tree_vector (p_in);
}
r = cp_build_modify_expr (fn_start, TREE_OPERAND (fld_idx, 0),
INIT_EXPR, arg, tf_warning_or_error);
else
{
if (!same_type_p (parm.frame_type, DECL_ARG_TYPE (arg)))
r = build1_loc (DECL_SOURCE_LOCATION (arg), CONVERT_EXPR,
parm.frame_type, arg);
else
r = arg;
r = build_modify_expr (fn_start, fld_idx, parm.frame_type,
INIT_EXPR, DECL_SOURCE_LOCATION (arg), r,
TREE_TYPE (r));
r = forward_parm (arg);
r = cp_build_modify_expr (fn_start, fld_idx, INIT_EXPR, r,
tf_warning_or_error);
}
finish_expr_stmt (r);
if (!parm.trivial_dtor)
@ -5044,16 +5006,8 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
DECL_IGNORED_P (gro) = true;
add_decl_expr (gro);
gro_bind_vars = gro;
if (type_build_ctor_call (gro_type))
{
vec<tree, va_gc> *arg = make_tree_vector_single (get_ro);
r = build_special_member_call (gro, complete_ctor_identifier,
&arg, gro_type, LOOKUP_NORMAL,
tf_warning_or_error);
release_tree_vector (arg);
}
else
r = build2_loc (fn_start, INIT_EXPR, gro_type, gro, get_ro);
r = cp_build_modify_expr (input_location, gro, INIT_EXPR, get_ro,
tf_warning_or_error);
/* The constructed object might require a cleanup. */
if (TYPE_HAS_NONTRIVIAL_DESTRUCTOR (gro_type))
{
@ -5111,37 +5065,26 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
if (same_type_p (gro_type, fn_return_type))
r = gro_is_void_p ? NULL_TREE : DECL_RESULT (orig);
else if (!gro_is_void_p)
/* check_return_expr will automatically return gro as an rvalue via
treat_lvalue_as_rvalue_p. */
r = gro;
else if (CLASS_TYPE_P (fn_return_type))
{
/* For class type return objects, we can attempt to construct,
even if the gro is void. ??? Citation ??? c++/100476 */
r = build_special_member_call (NULL_TREE,
complete_ctor_identifier, NULL,
fn_return_type, LOOKUP_NORMAL,
tf_warning_or_error);
r = build_cplus_new (fn_return_type, r, tf_warning_or_error);
}
else
{
if (CLASS_TYPE_P (fn_return_type))
{
/* For class type return objects, we can attempt to construct,
even if the gro is void. */
vec<tree, va_gc> *args = NULL;
vec<tree, va_gc> **arglist = NULL;
if (!gro_is_void_p)
{
args = make_tree_vector_single (rvalue (gro));
arglist = &args;
}
r = build_special_member_call (NULL_TREE,
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);
if (args)
release_tree_vector (args);
}
else if (gro_is_void_p)
{
/* We can't initialize a non-class return value from void. */
error_at (input_location, "cannot initialize a return object of type"
" %qT with an rvalue of type %<void%>", fn_return_type);
r = error_mark_node;
}
else
r = build1_loc (input_location, CONVERT_EXPR,
fn_return_type, rvalue (gro));
/* We can't initialize a non-class return value from void. */
error_at (input_location, "cannot initialize a return object of type"
" %qT with an rvalue of type %<void%>", fn_return_type);
r = error_mark_node;
}
finish_return_stmt (r);

2
gcc/testsuite/g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C
View file

@ -37,7 +37,7 @@ my_coro (std::coroutine_handle<>& h)
{
PRINT ("coro1: about to return");
co_return;
} // { dg-error {'struct Thing' used where a 'int' was expected} }
} // { dg-error {cannot convert 'Thing' to 'int' in return} }
int main ()
{