>From 5a69dd4e2e80fa8b9f2ed85be2fd7b647f8daec7 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Tue, 6 Oct 2026 13:36:13 -0400
Subject: [PATCH 6/6] fnmatch: do collation comparisons for equivalence classes
 and ranges

the primary-level-only comparisons needed here are implemented by
treating wcscoll as a black box, assuming only that non-character
codepoints U+10FFFE and U+10FFFF have distinct implicit primary
weights.

only single-character collating elements are supported. in the absence
of working space to build an NFA representation of the pattern,
multi-character collating elements seem to require a backtracking
(exponential time) approach to matching, which is not viable.
---
 src/regex/fnmatch.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/regex/fnmatch.c b/src/regex/fnmatch.c
index f93369e6..6758bd6e 100644
--- a/src/regex/fnmatch.c
+++ b/src/regex/fnmatch.c
@@ -107,10 +107,27 @@ static int casefold(int k)
 	return c == k ? towlower(k) : c;
 }
 
+static int cmp(int a, int b, int collation_order)
+{
+	if (!collation_order)
+		return a-b;
+	/* Append non-characters with a known implicit primary weight order
+	 * in order to detect differences that are only post-primary-level. */
+	wchar_t ac[3] = { a, 0x10fffe };
+	wchar_t bc[3] = { b, 0x10ffff };
+	int d1 = wcscoll(ac, bc);
+	ac[1]++;
+	bc[1]--;
+	int d2 = wcscoll(ac, bc);
+	if (d1 != d2) return 0;
+	return d1;
+}
+
 static int match_bracket(const char *p, int k, int kfold, int esc_ch)
 {
 	wchar_t wc;
 	int inv = 0;
+	int is_cs = 0, is_eq = 0;
 	p++;
 	if (*p=='^' || *p=='!') {
 		inv = 1;
@@ -126,7 +143,10 @@ static int match_bracket(const char *p, int k, int kfold, int esc_ch)
 	wc = p[-1];
 	for (; *p != ']'; p++) {
 		wchar_t wc0 = wc;
+		int is_cs_0 = is_cs;
 		int is_range = 0;
+		is_cs = 0;
+		is_eq = 0;
 		if (p[0]=='-' && p[1]!=']') {
 			is_range = 1;
 			p++;
@@ -151,6 +171,8 @@ static int match_bracket(const char *p, int k, int kfold, int esc_ch)
 			if (*p0 == esc_ch) p0++;
 			int l = mbtowc(&wc, p0, 4);
 			if (l != p-1-p0) continue;
+			is_cs = 1;
+			if (z=='=') is_eq = 1;
 		} else {
 			if (*p == esc_ch) p++;
 			if (*p < 128U) {
@@ -162,10 +184,14 @@ static int match_bracket(const char *p, int k, int kfold, int esc_ch)
 			}
 		}
 		if (is_range) {
-			if ((k>=wc0 && k<=wc) || (kfold>=wc0 && kfold<=wc))
+			if (cmp(k, wc0, is_cs_0)>=0 && cmp(k, wc, is_cs)<=0)
+				return !inv;
+			if (kfold != k && cmp(kfold, wc0, is_cs_0)>=0 && cmp(kfold, wc, is_cs)<=0)
 				return !inv;
 		} else if (p[1]!='-' || p[2]==']') {
-			if (wc==k || wc==kfold)
+			if (!cmp(k, wc, is_eq))
+				return !inv;
+			if (kfold != k && !cmp(kfold, wc, is_eq))
 				return !inv;
 		}
 	}
-- 
2.21.0