1 files changed, 49 insertions, 0 deletions
diff --git a/unit-tests/var-recursive.mk b/unit-tests/var-recursive.mk
new file mode 100644
index 000000000000..da1fb696d655
--- /dev/null
+++ b/unit-tests/var-recursive.mk
@@ -0,0 +1,49 @@
+# $NetBSD: var-recursive.mk,v 1.2 2020/10/31 13:45:00 rillig Exp $
+#
+# Tests for variable expressions that refer to themselves and thus
+# cannot be evaluated.
+
+TESTS=	direct indirect conditional short
+
+# Since make exits immediately when it detects a recursive expression,
+# the actual tests are run in sub-makes.
+TEST?=	# none
+.if ${TEST} == ""
+all:
+.for test in ${TESTS}
+	@${.MAKE} -f ${MAKEFILE} TEST=${test} || :
+.endfor
+
+.elif ${TEST} == direct
+
+DIRECT=	${DIRECT}	# Defining a recursive variable is not yet an error.
+.  info still there	# Therefore this line is printed.
+.  info ${DIRECT}	# But expanding the variable is an error.
+
+.elif ${TEST} == indirect
+
+# The chain of variables that refer to each other may be long.
+INDIRECT1=	${INDIRECT2}
+INDIRECT2=	${INDIRECT1}
+.  info ${INDIRECT1}
+
+.elif ${TEST} == conditional
+
+# The variable refers to itself, but only in the branch of a condition that
+# is never satisfied and is thus not evaluated.
+CONDITIONAL=	${1:?ok:${CONDITIONAL}}
+.  info ${CONDITIONAL}
+
+.elif ${TEST} == short
+
+# Short variable names can be expanded using the short-hand $V notation,
+# which takes a different code path in Var_Parse for parsing the variable
+# name.  Ensure that these are checked as well.
+V=	$V
+.  info $V
+
+.else
+.  error Unknown test "${TEST}"
+.endif
+
+all: