@@ -1348,6 +1348,7 @@ struct coro_aw_data
tree actor_fn; /* Decl for context. */
tree coro_fp; /* Frame pointer var. */
tree resume_idx; /* This is the index var in the frame. */
+ tree iarc_idx; /* This is the initial await resume called index. */
tree self_h; /* This is a handle to the current coro (frame var). */
tree cleanup; /* This is where to go once we complete local destroy. */
tree cororet; /* This is where to go if we suspend. */
@@ -1445,6 +1446,8 @@ co_await_expander (tree *stmt, int * /*do_subtree*/, void *d)
tree awaiter_calls = TREE_OPERAND (saved_co_await, 3);
tree source = TREE_OPERAND (saved_co_await, 4);
+ bool is_initial =
+ (source && TREE_INT_CST_LOW (source) == (int) INITIAL_SUSPEND_POINT);
bool is_final = (source
&& TREE_INT_CST_LOW (source) == (int) FINAL_SUSPEND_POINT);
bool needs_dtor = TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (var));
@@ -1586,6 +1589,16 @@ co_await_expander (tree *stmt, int * /*do_subtree*/, void *d)
resume_label = build_stmt (loc, LABEL_EXPR, resume_label);
append_to_statement_list (resume_label, &stmt_list);
+ if (is_initial)
+ {
+ /* Note that we are about to execute the await_resume() for the initial
+ await expression. */
+ r = build2_loc (loc, MODIFY_EXPR, boolean_type_node, data->iarc_idx,
+ boolean_true_node);
+ r = coro_build_cvt_void_expr_stmt (r, loc);
+ append_to_statement_list (r, &stmt_list);
+ }
+
/* This will produce the value (if one is provided) from the co_await
expression. */
tree resume_call = TREE_VEC_ELT (awaiter_calls, 2); /* await_resume(). */
@@ -1634,10 +1647,10 @@ co_await_expander (tree *stmt, int * /*do_subtree*/, void *d)
static tree
expand_co_awaits (tree fn, tree *fnbody, tree coro_fp, tree resume_idx,
- tree cleanup, tree cororet, tree self_h)
+ tree iarc_idx, tree cleanup, tree cororet, tree self_h)
{
coro_aw_data data
- = {fn, coro_fp, resume_idx, self_h, cleanup, cororet, 2};
+ = {fn, coro_fp, resume_idx, iarc_idx, self_h, cleanup, cororet, 2};
cp_walk_tree (fnbody, co_await_expander, &data, NULL);
return *fnbody;
}
@@ -2158,8 +2171,7 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
/* Get a reference to the initial suspend var in the frame. */
transform_await_expr (initial_await, &xform);
- r = coro_build_expr_stmt (initial_await, loc);
- add_stmt (r);
+ tree initial_await_stmt = coro_build_expr_stmt (initial_await, loc);
/* co_return branches to the final_suspend label, so declare that now. */
tree fs_label = create_named_label_with_ctx (loc, "final.suspend", actor);
@@ -2167,6 +2179,34 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
/* Expand co_returns in the saved function body */
fnbody = expand_co_returns (&fnbody, promise_proxy, ap, fs_label);
+ /* n4849 adds specific behaviour to treat exceptions thrown by the
+ await_resume () of the initial suspend expression. In order to
+ implement this, we need to treat the initial_suspend expression
+ as if it were part of the user's authored function body. This
+ only applies if exceptions are enabled. */
+ if (flag_exceptions)
+ {
+ tree outer = fnbody;
+ if (TREE_CODE (outer) == BIND_EXPR)
+ outer = BIND_EXPR_BODY (outer);
+ gcc_checking_assert (TREE_CODE (outer) == TRY_BLOCK);
+ tree sl = TRY_STMTS (outer);
+ if (TREE_CODE (sl) == STATEMENT_LIST)
+ {
+ tree_stmt_iterator si = tsi_start (sl);
+ tsi_link_before (&si, initial_await_stmt, TSI_NEW_STMT);
+ }
+ else
+ {
+ tree new_try = NULL_TREE;
+ append_to_statement_list (initial_await_stmt, &new_try);
+ append_to_statement_list (sl, &new_try);
+ TRY_STMTS (outer) = new_try;
+ }
+ }
+ else
+ add_stmt (initial_await_stmt);
+
/* Transform the await expressions in the function body. Only do each
await tree once! */
hash_set<tree> pset;
@@ -2336,10 +2376,18 @@ build_actor_fn (location_t loc, tree coro_frame_type, tree actor, tree fnbody,
= build_class_member_access_expr (actor_frame, res_idx_m, NULL_TREE, false,
tf_warning_or_error);
+ /* We need the initial await resume called index to work with. */
+ tree iarc_idx_m
+ = lookup_member (coro_frame_type, get_identifier ("__i_a_r_c"),
+ /*protect=*/1, /*want_type=*/0, tf_warning_or_error);
+ tree iarc_idx
+ = build_class_member_access_expr (actor_frame, iarc_idx_m, NULL_TREE,
+ false, tf_warning_or_error);
+
/* We've now rewritten the tree and added the initial and final
co_awaits. Now pass over the tree and expand the co_awaits. */
actor_body = expand_co_awaits (actor, &actor_body, actor_fp, res_idx,
- del_promise_label, ret_label, ash);
+ iarc_idx, del_promise_label, ret_label, ash);
actor_body = pop_stmt_list (actor_body);
BIND_EXPR_BODY (actor_bind) = actor_body;
@@ -3040,6 +3088,7 @@ act_des_fn (tree orig, tree fn_type, tree coro_frame_ptr, const char* name)
void (*__destroy)(_R_frame *);
coro1::promise_type __p;
bool frame_needs_free; free the coro frame mem if set.
+ bool i_a_r_c; [dcl.fct.def.coroutine] / 5.3
short __resume_at;
handle_type self_handle;
(maybe) parameter copies.
@@ -3161,6 +3210,8 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
= coro_make_frame_entry (&field_list, "__p", promise_type, fn_start);
tree fnf_name = coro_make_frame_entry (&field_list, "__frame_needs_free",
boolean_type_node, fn_start);
+ tree iarc_name = coro_make_frame_entry (&field_list, "__i_a_r_c",
+ boolean_type_node, fn_start);
tree resume_idx_name
= coro_make_frame_entry (&field_list, "__resume_at",
short_unsigned_type_node, fn_start);
@@ -3725,6 +3776,16 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
r = coro_build_cvt_void_expr_stmt (r, fn_start);
add_stmt (r);
+ /* Initialize 'initial-await-resume-called' as per
+ [dcl.fct.def.coroutine] / 5.3 */
+ tree iarc_m
+ = lookup_member (coro_frame_type, iarc_name, 1, 0, tf_warning_or_error);
+ tree iarc_x = build_class_member_access_expr (deref_fp, iarc_m, NULL_TREE,
+ false, tf_warning_or_error);
+ r = build2 (INIT_EXPR, boolean_type_node, iarc_x, boolean_false_node);
+ r = coro_build_cvt_void_expr_stmt (r, fn_start);
+ add_stmt (r);
+
/* So .. call the actor .. */
r = build_call_expr_loc (fn_start, actor, 1, coro_fp);
r = maybe_cleanup_point_expr_void (r);
@@ -3845,6 +3906,25 @@ morph_fn_to_coro (tree orig, tree *resumer, tree *destroyer)
/* Mimic what the parser does for the catch. */
tree handler = begin_handler ();
finish_handler_parms (NULL_TREE, handler); /* catch (...) */
+
+ /* Get the initial await resume called value. */
+ tree iarc = build_class_member_access_expr (actor_frame, iarc_m,
+ NULL_TREE, false,
+ tf_warning_or_error);
+ tree not_iarc_if = begin_if_stmt ();
+ tree not_iarc = build1_loc (fn_start, TRUTH_NOT_EXPR,
+ boolean_type_node, iarc);
+ finish_if_stmt_cond (not_iarc, not_iarc_if);
+ /* If the initial await resume called value is false, rethrow... */
+ tree rethrow = build_throw (fn_start, NULL_TREE);
+ TREE_NO_WARNING (rethrow) = true;
+ finish_expr_stmt (rethrow);
+ finish_then_clause (not_iarc_if);
+ tree iarc_scope = IF_SCOPE (not_iarc_if);
+ IF_SCOPE (not_iarc_if) = NULL;
+ not_iarc_if = do_poplevel (iarc_scope);
+ add_stmt (not_iarc_if);
+ /* ... else call the promise unhandled exception method. */
ueh = maybe_cleanup_point_expr_void (ueh);
add_stmt (ueh);
finish_handler (handler);
new file mode 100644
@@ -0,0 +1,213 @@
+// { dg-do run }
+
+// Test exceptions in the initial await expression, per n4849.
+
+#include "../coro.h"
+#include <exception>
+
+int gX = 0;
+
+struct coro1 {
+ struct promise_type;
+ using handle_type = coro::coroutine_handle<coro1::promise_type>;
+ handle_type handle;
+
+ coro1 () : handle(0) {}
+ coro1 (handle_type _handle)
+ : handle(_handle) {
+ PRINT("Created coro1 object from handle");
+ }
+ coro1 (const coro1 &) = delete; // no copying
+ coro1 (coro1 &&s) : handle(s.handle) {
+ s.handle = nullptr;
+ PRINT("coro1 mv ctor ");
+ }
+ coro1 &operator = (coro1 &&s) {
+ handle = s.handle;
+ s.handle = nullptr;
+ PRINT("coro1 op= ");
+ return *this;
+ }
+ ~coro1() {
+ PRINT("Destroyed coro1");
+ if ( handle )
+ handle.destroy();
+ }
+
+ struct suspend_never_prt {
+ bool await_ready() const noexcept { return true; }
+ void await_suspend(handle_type) const noexcept { PRINT ("susp-never-susp"); }
+ void await_resume() const noexcept { PRINT ("susp-never-resume");}
+ };
+
+ struct suspend_always_prt {
+ bool await_ready() const noexcept { return false; }
+ void await_suspend(handle_type) const noexcept { PRINT ("susp-always-susp"); }
+ void await_resume() const noexcept { PRINT ("susp-always-resume"); }
+ ~suspend_always_prt() { PRINT ("susp-always-DTOR"); }
+ };
+
+ /* Constructing this with:
+ * a value of '1' will cause the initial suspend await_suspend()
+ call to throw.
+ * a value of '2' will cause the await resume to throw. */
+ struct suspend_always_susp_throws_prt {
+ int thrower;
+ suspend_always_susp_throws_prt (int _t) : thrower(_t) {}
+ bool await_ready() const noexcept { return false; }
+
+ void await_suspend(handle_type) const
+ { PRINT ("suspend_always_susp_throws_prt:await_suspend");
+ if (thrower == 1)
+ throw (42);
+ }
+ void await_resume() const
+ { PRINT ("suspend_always_susp_throws_prt:await_resume");
+ if (thrower == 2)
+ throw (6174);
+ }
+ ~suspend_always_susp_throws_prt() { PRINT ("suspend_always_susp_throws_prt-DTOR"); }
+ };
+
+ struct promise_type {
+ int throw_control = 0;
+ int value;
+ promise_type(int k) : throw_control(k), value(-373)
+ { PRINTF ("Created Promise with %d\n", k);}
+
+ ~promise_type() { PRINT ("Destroyed Promise"); }
+
+ auto get_return_object () {
+ PRINT ("get_return_object: handle from promise");
+ return handle_type::from_promise (*this);
+ }
+ // This provides the tests for what catches exceptions thrown at
+ // different points in the initial await expression.
+ auto initial_suspend () {
+ PRINT ("get initial_suspend (always)");
+ return suspend_always_susp_throws_prt(throw_control);
+ }
+ auto final_suspend () {
+ PRINT ("get final_suspend (always)");
+ return suspend_always_prt{};
+ }
+ void return_value (int v) {
+ PRINTF ("return_value () %d\n",v);
+ value = v;
+ }
+ auto yield_value (int v) {
+ PRINTF ("yield_value () %d and suspend always\n",v);
+ value = v;
+ return suspend_always_prt{};
+ }
+ int get_value (void) { return value; }
+
+ void unhandled_exception() {
+ PRINT ("unhandled_exception: caught one!");
+ gX = -11;
+ // returning from here should end up in final_suspend.
+ }
+ };
+};
+
+// This doesn't have to do much - we only need to exercise the initial
+// await expression.
+
+struct coro1
+n4849_ia_thrower (int k)
+{
+ int caught = 0;
+ PRINT ("f: about to return 22");
+ co_return 22;
+}
+
+int main ()
+{
+ {
+ /* Case 0 - nothing should throw. */
+ struct coro1 x0;
+ try {
+ x0 = n4849_ia_thrower (0);
+ } catch (...) {
+ PRINT ("main: case 0 ctor threw?");
+ abort ();
+ }
+ /* Resume the initial suspend expression. */
+ PRINT ("main: got coro, resuming..");
+ x0.handle.resume();
+ int y = x0.handle.promise().get_value();
+ if ( y != 22 )
+ {
+ PRINT ("main: case 0 got the wrong answer.");
+ abort ();
+ }
+ if (!x0.handle.done())
+ {
+ PRINT ("main: case 0 not done.");
+ abort ();
+ }
+ if (gX != 0)
+ {
+ PRINT ("main: case 0 body threw?");
+ abort ();
+ }
+ }
+
+ {
+ /* Case 1 - initial suspend should throw and thus be caught by the
+ ramp's caller. */
+ struct coro1 x1;
+ try {
+ x1 = n4849_ia_thrower (1);
+ } catch (int message) {
+ PRINTF ("main: caught an int %d\n", message);
+ if (message != 42)
+ {
+ PRINT ("main: unexpected value?");
+ abort ();
+ }
+ } catch (...) {
+ PRINT ("main: case 1 ctor threw something else?");
+ abort ();
+ }
+ if (gX != 0)
+ {
+ PRINT ("main: case 0 body threw (how?)");
+ abort ();
+ }
+ }
+
+ {
+ /* Case 2 - the await_resume from the initial await expression throws
+ this should be caught by the regular function body wrapper. */
+ struct coro1 x2;
+ try {
+ x2 = n4849_ia_thrower (2);
+ } catch (...) {
+ PRINT ("main: case 2 ctor threw?");
+ abort ();
+ }
+ // We now resume - and expect the await_resume to throw which should
+ // be caught by unhandled_exception().
+ PRINT ("main: got coro, resuming..");
+ x2.handle.resume();
+ int y = x2.handle.promise().get_value();
+ if ( y != -373 )
+ {
+ PRINT ("main: case 2 got the wrong answer.");
+ abort ();
+ }
+ if (!x2.handle.done())
+ {
+ PRINT ("main: case 2 not done.");
+ abort ();
+ }
+ if (gX != -11)
+ {
+ PRINT ("main: n4849_is_thrower await_resume exception not caught");
+ abort ();
+ }
+ }
+ PRINT ("main: returning");
+ return 0;
+}
Hi, This is the first of two remaining changes needed to bring the GCC implementation into line with the standard draft at n4849. The standard now calls up a revised mechanism to handle exceptions where exceptions thrown by the await_resume () method of the initial suspend expression are considered in the same manner as exceptions thrown by the user's function body. This implements [dcl.fct.def.coroutine] / 5.3. tested on x86_64-{linux, darwin} powerpc-linux, OK for master? thanks Iain gcc/cp/ChangeLog: 2020-03-20 Iain Sandoe <iain@sandoe.co.uk> * coroutines.cc (co_await_expander): If we are expanding the initial await expression, set a boolean flag to show that we have now reached the initial await_resume() method call. (expand_co_awaits): Handle the 'initial await resume called' flag. (build_actor_fn): Insert the initial await expression into the start of the user's function-body. Handle the 'initial await resume called' flag. (morph_fn_to_coro): Initialise the 'initial await resume called' flag. Modify the unhandled exception catch clause to recognise exceptions that occur before the initial await_resume() and re- throw them. gcc/testsuite/ChangeLog: 2020-03-20 Iain Sandoe <iain@sandoe.co.uk> * g++.dg/coroutines/torture/exceptions-test-01-n4849-a.C: New test.