[PATCH 2/2] regex: pacify 16.1.1 -Wanalyzer-out-of-bounds

* lib/regex_internal.c (re_node_set_insert): Add a DEBUG_ASSERT.
Needed for gcc 16.1.1 20260515 (Red Hat 16.1.1-2) on x86-64 when
_REGEX_AVOID_UCHAR_H is defined.
---
 ChangeLog            | 5 +++++
 lib/regex_internal.c | 8 +++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 169ee053dd..556c9bf5b5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2026-05-24  Paul Eggert  <[email protected]>
 
+	regex: pacify 16.1.1 -Wanalyzer-out-of-bounds
+	* lib/regex_internal.c (re_node_set_insert): Add a DEBUG_ASSERT.
+	Needed for gcc 16.1.1 20260515 (Red Hat 16.1.1-2) on x86-64 when
+	_REGEX_AVOID_UCHAR_H is defined.
+
 	regex: new _REGEX_AVOID_UCHAR_H option
 	This is for GNU Emacs, where the regex code is only auxiliary,
 	probably not enough to justify the hassle of incorporating
diff --git a/lib/regex_internal.c b/lib/regex_internal.c
index ad1b273546..e5e5be84bd 100644
--- a/lib/regex_internal.c
+++ b/lib/regex_internal.c
@@ -1285,7 +1285,13 @@ re_node_set_insert (re_node_set *set, Idx elem)
   else
     {
       for (idx = set->nelem; set->elems[idx - 1] > elem; idx--)
-	set->elems[idx] = set->elems[idx - 1];
+        {
+          set->elems[idx] = set->elems[idx - 1];
+          /* Although we already guaranteed that idx is at least 2 here,
+             add an assertion to pacify GCC 16.1.1 -Wanalyzer-out-of-bounds
+             when _REGEX_AVOID_UCHAR_H is defined.  */
+          DEBUG_ASSERT (1 < idx);
+        }
       /* Already in set.  Return early.  */
       if (__glibc_unlikely (set->elems[idx - 1] == elem))
 	return true;
-- 
2.54.0