diff --git a/lib/libc/tests/gen/Makefile b/lib/libc/tests/gen/Makefile
--- a/lib/libc/tests/gen/Makefile
+++ b/lib/libc/tests/gen/Makefile
@@ -19,6 +19,7 @@
 .if ${COMPILER_FEATURES:Mblocks}
 ATF_TESTS_C+=		glob_blocks_test
 .endif
+ATF_TESTS_C+=		limits_test
 ATF_TESTS_C+=		makecontext_test
 ATF_TESTS_C+=		opendir_test
 ATF_TESTS_C+=		popen_test
diff --git a/lib/libc/tests/gen/limits_test.c b/lib/libc/tests/gen/limits_test.c
new file mode 100644
--- /dev/null
+++ b/lib/libc/tests/gen/limits_test.c
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
+ *
+ * SPDX-License-Identifier: FreeBSD-2-Clause
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <signal.h>
+#include <stdint.h>
+#include <wchar.h>
+
+#include <atf-c.h>
+
+/* if this file builds, the unit tests have passed */
+#define CHECK_STYPE(type, TYPE)						\
+	static_assert(sizeof(type) * CHAR_BIT == TYPE ## _WIDTH,	\
+		__XSTRING(TYPE) "_WIDTH wrongly defined");		\
+	static_assert((1ULL << (TYPE ## _WIDTH - 1)) - 1 == TYPE ## _MAX, \
+		__XSTRING(TYPE) "_MAX wrongly defined");		\
+	static_assert(TYPE ## _MIN == -TYPE ## _MAX - 1, \
+		__XSTRING(TYPE) "_MIN wrongly defined")
+#define CHECK_UTYPE(type, TYPE)						\
+	static_assert(sizeof(type) * CHAR_BIT == TYPE ## _WIDTH,	\
+		__XSTRING(TYPE) "_WIDTH wrongly defined");		\
+	static_assert((type)~0ULL == TYPE ## _MAX,			\
+		__XSTRING(TYPE) "_MAX wrongly defined");
+
+/* primitive types */
+#ifdef __CHAR_UNSIGNED__
+CHECK_UTYPE(char, CHAR);
+#else
+CHECK_STYPE(char, CHAR);
+#endif
+
+CHECK_STYPE(signed char, SCHAR);
+CHECK_STYPE(short, SHRT);
+CHECK_STYPE(int, INT);
+CHECK_STYPE(long, LONG);
+CHECK_STYPE(long long, LLONG);
+
+CHECK_UTYPE(unsigned char, UCHAR);
+CHECK_UTYPE(unsigned short, USHRT);
+CHECK_UTYPE(unsigned int, UINT);
+CHECK_UTYPE(unsigned long, ULONG);
+CHECK_UTYPE(unsigned long long, ULLONG);
+
+/* fixed-width types */
+CHECK_STYPE(int8_t, INT8);
+CHECK_STYPE(int16_t, INT16);
+CHECK_STYPE(int32_t, INT32);
+CHECK_STYPE(int64_t, INT64);
+
+CHECK_UTYPE(uint8_t, UINT8);
+CHECK_UTYPE(uint16_t, UINT16);
+CHECK_UTYPE(uint32_t, UINT32);
+CHECK_UTYPE(uint64_t, UINT64);
+
+CHECK_STYPE(int_least8_t, INT_LEAST8);
+CHECK_STYPE(int_least16_t, INT_LEAST16);
+CHECK_STYPE(int_least32_t, INT_LEAST32);
+CHECK_STYPE(int_least64_t, INT_LEAST64);
+
+CHECK_UTYPE(uint_least8_t, UINT_LEAST8);
+CHECK_UTYPE(uint_least16_t, UINT_LEAST16);
+CHECK_UTYPE(uint_least32_t, UINT_LEAST32);
+CHECK_UTYPE(uint_least64_t, UINT_LEAST64);
+
+CHECK_STYPE(int_fast8_t, INT_FAST8);
+CHECK_STYPE(int_fast16_t, INT_FAST16);
+CHECK_STYPE(int_fast32_t, INT_FAST32);
+CHECK_STYPE(int_fast64_t, INT_FAST64);
+
+CHECK_UTYPE(uint_fast8_t, UINT_FAST8);
+CHECK_UTYPE(uint_fast16_t, UINT_FAST16);
+CHECK_UTYPE(uint_fast32_t, UINT_FAST32);
+CHECK_UTYPE(uint_fast64_t, UINT_FAST64);
+
+/* other types */
+#if WCHAR_MIN == 0
+CHECK_UTYPE(wchar_t, WCHAR);
+#else
+CHECK_STYPE(wchar_t, WCHAR);
+#endif
+CHECK_STYPE(intmax_t, INTMAX);
+CHECK_STYPE(intptr_t, INTPTR);
+CHECK_STYPE(ptrdiff_t, PTRDIFF);
+CHECK_STYPE(wint_t, WINT);
+CHECK_STYPE(sig_atomic_t, SIG_ATOMIC);
+
+CHECK_UTYPE(uintmax_t, UINTMAX);
+CHECK_UTYPE(uintptr_t, UINTPTR);
+CHECK_UTYPE(size_t, SIZE);
+
+/* dummy */
+ATF_TP_ADD_TCS(tp)
+{
+	(void)tp;
+
+	return (atf_no_error());
+}