[gcc r16-589] libiberty: Fix off-by-one when collecting range expression

[Andreas Schwab]

https://gcc.gnu.org/g:43717ee9064e73d0ad0cfb4f8f937ba9f5cbcc51

commit r16-589-g43717ee9064e73d0ad0cfb4f8f937ba9f5cbcc51
Author: Andreas Schwab <schwab@suse.de>
Date:   Wed May 7 09:46:19 2025 +0200

    libiberty: Fix off-by-one when collecting range expression
    
    Fixes this error during build of fixincludes:
    
    In function ‘byte_regex_compile’,
        inlined from ‘xregcomp’ at ../libiberty/../../libiberty/regex.c:7973:11:
    ../libiberty/../../libiberty/regex.c:3477:29: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
     3477 |                     str[c1] = '\0';
          |                             ^
    ../libiberty/../../libiberty/regex.c: In function ‘xregcomp’:
    ../libiberty/../../libiberty/regex.c:3454:35: note: at offset 128 into destination object ‘str’ of size 128
     3454 |                     unsigned char str[128];     /* Should be large enough.  */
          |                                   ^
    
            * regex.c (regex_compile): Don't write beyond array bounds when
            collecting range expression.

Diff:
---
 libiberty/regex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libiberty/regex.c b/libiberty/regex.c
index bc36f43d450a..8337deaef5af 100644
--- a/libiberty/regex.c
+++ b/libiberty/regex.c
@@ -3468,7 +3468,7 @@ PREFIX(regex_compile) (const char *ARG_PREFIX(pattern),
 			PATFETCH (c);
 			if ((c == '.' && *p == ']') || p == pend)
 			  break;
-			if (c1 < sizeof (str))
+			if (c1 < sizeof (str) - 1)
 			  str[c1++] = c;
 			else
 			  /* This is in any case an invalid class name.  */