From: Marek Polacek <polacek@redhat.com>
Date: Thu, 22 Jan 2026 20:52:45 +0000 (-0500)
Subject: c++/reflection: detect more invalid splices in lambda
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f3bf6e14360d7a6d5ecca494b94a2165a97ec34c;p=thirdparty%2Fgcc.git

c++/reflection: detect more invalid splices in lambda

The comment for check_splice_expr in
<https://gcc.gnu.org/pipermail/gcc-patches/2025-December/704168.html>
points out that I wasn't giving an error for this testcase.  (clang++
rejects the testcase.)

Fixed by checking if process_outer_var_ref returned a capture.

gcc/cp/ChangeLog:

	* reflect.cc (check_splice_expr): Check if process_outer_var_ref
	returned a capture, and give an error if so.

gcc/testsuite/ChangeLog:

	* g++.dg/reflect/expr15.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 2f9aa36c787..bdeec2f0f38 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -8395,20 +8395,21 @@ check_splice_expr (location_t loc, location_t start_loc, tree t,
      -- a local entity such that there is a lambda scope that intervenes
      between the expression and the point at which S was introduced"
      This also checks ODR violations (reflect/odr1.C).  */
-  if (outer_automatic_var_p (t)
-      && process_outer_var_ref (t, tf_none) == error_mark_node)
-    {
-      /* Not letting process_outer_var_ref emit the error so that we can
-	 say "in a splice expression".  */
-      if (complain_p)
+  if (outer_automatic_var_p (t))
+    if (tree r = process_outer_var_ref (t, tf_none))
+      if (r == error_mark_node || is_capture_proxy (r))
 	{
-	  auto_diagnostic_group d;
-	  error_at (loc, "use of local variable with automatic storage from "
-		    "containing function in a splice expression");
-	  inform (DECL_SOURCE_LOCATION (t), "%q#D declared here", t);
+	  /* Not letting process_outer_var_ref emit the error so that we can
+	     say "in a splice expression".  */
+	  if (complain_p)
+	    {
+	      auto_diagnostic_group d;
+	      error_at (loc, "use of local variable with automatic storage "
+			"from containing function in a splice expression");
+	      inform (DECL_SOURCE_LOCATION (t), "%q#D declared here", t);
+	    }
+	  return false;
 	}
-      return false;
-    }
 
   /* If we had a reflect_kind here, we could just check for
      REFLECT_ANNOTATION and be done with it.  But we don't have it yet (TODO),
diff --git a/gcc/testsuite/g++.dg/reflect/expr15.C b/gcc/testsuite/g++.dg/reflect/expr15.C
new file mode 100644
index 00000000000..41da34f00f0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/expr15.C
@@ -0,0 +1,22 @@
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+void
+f1 ()
+{
+  int x = 1; // { dg-message ".x. declared here" }
+  constexpr auto r = ^^x;
+  [=] -> decltype(x) {
+    return [:r:]; // { dg-error "use of local variable" }
+  };
+}
+
+void
+f2 ()
+{
+  int x = 1; // { dg-message ".x. declared here" }
+  constexpr auto r = ^^x;
+  [&] -> decltype(x) {
+    return [:r:]; // { dg-error "use of local variable" }
+  };
+}