CONFIGURATION!

scripts/kconfig/tests/preprocess/circular_expansion/Kconfig

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+X = $(Y)
+Y = $(X)
+$(info $(X))

scripts/kconfig/tests/preprocess/circular_expansion/__init__.py

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+"""
+Detect circular variable expansion.
+
+If a recursively expanded variable references itself (eventually),
+it should fail with an error message.
+"""
+
+def test(conf):
+    assert conf.oldaskconfig() != 0
+    assert conf.stderr_matches('expected_stderr')

scripts/kconfig/tests/preprocess/circular_expansion/expected_stderr

@@ -0,0 +1 @@
+Kconfig:5: Recursive variable 'X' references itself (eventually)