From 0a0ca17c3d6a77fc36f96189ccff9be12af66e63 Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Tue, 4 Jun 2024 13:41:06 -0400
Subject: track LC_CTYPE epoch in character conversion functions to detect a
 change

---
 src/locale/_locale.h |  2 ++
 src/stdlib/_stdlib.h | 14 ++++++++++++++
 src/stdlib/mblen.c   |  1 +
 src/stdlib/mbtowc.c  |  1 +
 src/stdlib/wctomb.c  |  1 +
 5 files changed, 19 insertions(+)

diff --git a/src/locale/_locale.h b/src/locale/_locale.h
index b7867731..623ca4f3 100644
--- a/src/locale/_locale.h
+++ b/src/locale/_locale.h
@@ -92,6 +92,8 @@ struct __locale_t {
 char * __load_locale(struct __locale_t *loc, int mask, const char *name);
 struct __locale_t * __get_locale(void);
 
+#define __get_ctype_epoch() (__get_locale()->ctype_epoch)
+
 /*
 STDC(-1)
 */
diff --git a/src/stdlib/_stdlib.h b/src/stdlib/_stdlib.h
index 7edb9d98..d5f89b09 100644
--- a/src/stdlib/_stdlib.h
+++ b/src/stdlib/_stdlib.h
@@ -3,8 +3,22 @@
 
 #include <stdlib.h>
 #include <limits.h>
+#include "locale/_locale.h"
 #include "_safety.h"
 
+#ifndef NDEBUG
+#define ASSERT_CTYPE(__s_ptr) do { \
+	static unsigned int __ctype_epoch = 0; \
+	if ((__s_ptr) == 0) { \
+		__ctype_epoch = __get_ctype_epoch(); \
+	} else if (__ctype_epoch != __get_ctype_epoch()) { \
+		UNDEFINED("LC_CTYPE has changed since previous call which did not reset internal state"); \
+	} \
+} while (0)
+#else
+#define ASSERT_CTYPE(__s_ptr) (void)(__s_ptr)
+#endif
+
 #ifdef NEED_COMPAR
 #ifdef NDEBUG
 #define SAFE_COMPAR(__comp, __p1, __p2, __sz, __fn) __comp(__p1, __p2)
diff --git a/src/stdlib/mblen.c b/src/stdlib/mblen.c
index 42188418..57f64790 100644
--- a/src/stdlib/mblen.c
+++ b/src/stdlib/mblen.c
@@ -6,6 +6,7 @@
 int mblen(const char * s, size_t n)
 {
 	SIGNAL_SAFE(0);
+	ASSERT_CTYPE(s);
 
 	/* FIXME: forward dependency on AMD1 */
 	#if 0
diff --git a/src/stdlib/mbtowc.c b/src/stdlib/mbtowc.c
index c2780bf6..57ae03b9 100644
--- a/src/stdlib/mbtowc.c
+++ b/src/stdlib/mbtowc.c
@@ -7,6 +7,7 @@ int mbtowc(wchar_t * restrict pwc, const char * restrict s, size_t n)
 {
 	SIGNAL_SAFE(0);
 	ASSERT_NOOVERLAP(pwc, sizeof(*pwc), s, n);
+	ASSERT_CTYPE(s);
 
 	/* FIXME: forward dependency on AMD1 */
 	#if 0
diff --git a/src/stdlib/wctomb.c b/src/stdlib/wctomb.c
index ce4c8e82..d1de2dd8 100644
--- a/src/stdlib/wctomb.c
+++ b/src/stdlib/wctomb.c
@@ -6,6 +6,7 @@
 int wctomb(char * s, wchar_t wchar)
 {
 	SIGNAL_SAFE(0);
+	ASSERT_CTYPE(s);
 
 	/* FIXME: forward dependency on AMD1 */
 	#if 0
-- 
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