Fix a warning with gcc 15 and glibc 2.43

[Bruno Haible via Bug reports for the GNU Texinfo documentation system]

Building texinfo-7.2.90 with gcc 15.2.0 and glibc 2.43 (that was released
yesterday), I see a warning:

../../install-info/install-info.c:1605:15: warning: initialization discards 
‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]

The cause is this change in glibc [1]:
  * For ISO C23, the functions bsearch, memchr, strchr, strpbrk, strrchr,
    strstr, wcschr, wcspbrk, wcsrchr, wcsstr and wmemchr that return
    pointers into their input arrays now have definitions as macros that
    return a pointer to a const-qualified type when the input argument is
    a pointer to a const-qualified type.

Here, ISO C 23 wants 'ptr' to be a 'const char *', not a 'char *'.
And with it, 'endptr' must be of the same type as well.

Find attached a proposed patch. I have verified that it fixes the warning.

[1] https://lists.gnu.org/archive/html/info-gnu/2026-01/msg00005.html


>From 053706be2cd2de3c3356307e637b84458fa63078 Mon Sep 17 00:00:00 2001
From: Bruno Haible <br...@clisp.org>
Date: Sun, 25 Jan 2026 02:32:01 +0100
Subject: [PATCH] install-info: Fix warning with gcc 15 and glibc 2.43.

* install-info/install-info.c (split_entry): Change type of ptr and endptr
to conform to ISO C 23.
---
 install-info/install-info.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/install-info/install-info.c b/install-info/install-info.c
index c690e01470..2fa2ecca99 100644
--- a/install-info/install-info.c
+++ b/install-info/install-info.c
@@ -1596,13 +1596,13 @@ static void
 split_entry (const char *entry, char **name, size_t *name_len,
              char **description, size_t *description_len)
 {
-  char *endptr;
+  const char *endptr;
 
   /* on the first line, the description starts after the first ". ";
      that's a period and space -- our heuristic to handle item names like
      "config.status", and node names like "config.status Invocation".
      Also accept period-tab and period-newline.  */
-  char *ptr = strchr (entry, '.');
+  const char *ptr = strchr (entry, '.');
   while (ptr && ptr[1] != ' ' && ptr[1] != '\t' && ptr[1] != '\n') {
     ptr = strchr (ptr + 1, '.');
   }
-- 
2.52.0