From a9309034d275a97956c0c8854e943e25cda57039 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Tue, 5 Nov 2024 21:11:02 +0100
Subject: [PATCH 09/23] strncat tests: Verify N3322 functionality.

* tests/test-strncat.c (main): Add a zero-size test.
---
 ChangeLog            |  5 +++++
 tests/test-strncat.c | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index b61465d749..15d587da21 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2024-11-05  Bruno Haible  <bruno@clisp.org>
+
+	strncat tests: Verify N3322 functionality.
+	* tests/test-strncat.c (main): Add a zero-size test.
+
 2024-11-05  Bruno Haible  <bruno@clisp.org>
 
 	strndup tests: Verify N3322 functionality.
diff --git a/tests/test-strncat.c b/tests/test-strncat.c
index 0ee5089e58..c4668d95b4 100644
--- a/tests/test-strncat.c
+++ b/tests/test-strncat.c
@@ -58,5 +58,21 @@ main ()
     check (input, SIZEOF (input));
   }
 
+  int volatile value;
+
+  /* Test zero-length operations on NULL pointers, allowed by
+     <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3322.pdf>.  */
+
+#if 0 /* I think this is invalid, per ISO C 23 § 7.26.3.2.  */
+  value = (strncat (NULL, "x", 0) == NULL);
+  ASSERT (value);
+#endif
+
+  {
+    char y[1];
+    value = (strncat (y, NULL, 0) == y);
+    ASSERT (value);
+  }
+
   return test_exit_status;
 }
-- 
2.34.1