From 78556fc13026220f800384accf04e139f11e099a Mon Sep 17 00:00:00 2001
From: Joan Bruguera <joanbrugueram@gmail.com>
Date: Thu, 17 Feb 2022 22:27:34 +0100
Subject: [PATCH] Workaround mbsrtowcs fortify crash in GLIBC 2.35

Reproduces with:
    gcc -O2 -Wp,-D_FORTIFY_SOURCE=2 test.c -o test && ./test

And test.c:
    #include <stdio.h>
    #include <stdlib.h>
    #include <wchar.h>

    int main (void)
    {
        const char *hw = "HelloWorld";
        mbstate_t ps = {0};
        mbsrtowcs (NULL, &hw, (size_t)-1, &ps);
        return 0;
    }

Output:
    *** buffer overflow detected ***: terminated
---
 utf8.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/utf8.c b/utf8.c
index 2db18f2..806d528 100644
--- a/utf8.c
+++ b/utf8.c
@@ -167,7 +167,7 @@ static size_t xmbstowcs (wchar_t *dest, const char *src, size_t len,
 	while (src && (len || !dest)) {
 		size_t res;
 
-		res = mbsrtowcs (dest, &src, len, &ps);
+		res = mbsrtowcs (dest, &src, dest ? len : 0, &ps);
 		if (res != (size_t)-1) {
 			count += res;
 			src = NULL;
-- 
2.35.1