On 5/20/26 3:06 AM, Jakub Jelinek wrote:
Hi!
For variables which do have non-NULL DECL_NAME, register_local_var_uses
uses either that name or name_depth_idx (that itself is a bug as it
can clash with user variables named that way) for the fields. In C++26
we can have multiple _ variables in the same scope, so the following
testcase is miscompiled by using the same FIELD_DECL multiple times
(once for the first _ variable, once for the second one).
The following patch fixes it by pretending such variables don't have
a name, so it uses a serial number then instead.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
2026-05-20 Jakub Jelinek <[email protected]>
PR c++/125376
* coroutines.cc (register_local_var_uses): Ignore DECL_NAME for
name independent decls.
* g++.dg/coroutines/pr125376.C: New test.
--- gcc/cp/coroutines.cc.jj 2026-04-15 16:05:43.251129289 +0200
+++ gcc/cp/coroutines.cc 2026-05-19 11:53:32.694832799 +0200
@@ -4403,6 +4403,8 @@ register_local_var_uses (tree *stmt, int
identify them in the coroutine frame. */
tree lvname = DECL_NAME (lvar);
char *buf = NULL;
+ if (name_independent_decl_p (lvar))
+ lvname = NULL_TREE;
/* The outermost bind scope contains the artificial variables that
we inject to implement the coro state machine. We want to be able
--- gcc/testsuite/g++.dg/coroutines/pr125376.C.jj 2026-05-19
12:00:40.335622834 +0200
+++ gcc/testsuite/g++.dg/coroutines/pr125376.C 2026-05-19 12:00:36.190692718
+0200
@@ -0,0 +1,40 @@
+// PR c++/125376
+// { dg-do run { target c++26 } }
+
+#include <coroutine>
+
+struct task {
+ struct promise_type {
+ task get_return_object () noexcept { return {}; }
+ std::suspend_never initial_suspend () noexcept { return {}; }
+ std::suspend_never final_suspend () noexcept { return {}; }
+ void return_void () noexcept {}
+ void unhandled_exception () {}
+ };
+};
+
+struct A {
+ unsigned value = 42;
+ A () {}
+ ~A () { if (value != 42) __builtin_abort (); }
+};
+
+struct B {
+ unsigned value = 43;
+ B () {}
+ ~B () { if (value != 43) __builtin_abort (); }
+};
+
+task
+foo ()
+{
+ auto _ = A {};
+ auto _ = B {};
+ co_return;
+}
+
+int
+main ()
+{
+ foo ();
+}
Jakub
