[PATCH] maint: handle C23 qualifier-generic strchr/strrchr

[Grisha Levit]

Building with GCC 15 produces warnings for usage of C23 qualifier-generic
functions like strchr/strrchr, e.g.:

    pathexp.c: In function ‘glob_name_is_acceptable’:
    pathexp.c:533:5: warning: assignment discards ‘const’ qualifier from 
pointer target type [-Wdiscarded-qualifiers]
      533 |   n = strrchr (name, '/');
          |     ^

See [1] for similar changes to gnulib.

[1] https://lists.gnu.org/r/bug-gnulib/2025-11/msg00220.html
---
 builtins/getopt.c        | 3 ++-
 examples/loadables/seq.c | 2 +-
 lib/sh/mbschr.c          | 2 +-
 lib/sh/utf8.c            | 2 +-
 pathexp.c                | 2 +-
 5 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/builtins/getopt.c b/builtins/getopt.c
index 47a8f77c..283de6a0 100644
--- a/builtins/getopt.c
+++ b/builtins/getopt.c
@@ -113,7 +113,8 @@ int sh_badopt = 0;
 int
 sh_getopt (int argc, char *const *argv, const char *optstring)
 {
-  char c, *temp;
+  char c;
+  const char *temp;
 
   sh_optarg = 0;
 
diff --git a/examples/loadables/seq.c b/examples/loadables/seq.c
index 13834b8d..89517c1d 100644
--- a/examples/loadables/seq.c
+++ b/examples/loadables/seq.c
@@ -171,7 +171,7 @@ static int
 getprec (const char *numbuf)
 {
   int p;
-  char *dp;
+  const char *dp;
 
   if (dp = strchr (numbuf, decimal_point))
     dp++;              /* skip over decimal point */
diff --git a/lib/sh/mbschr.c b/lib/sh/mbschr.c
index f86ea0bb..4d24eb65 100644
--- a/lib/sh/mbschr.c
+++ b/lib/sh/mbschr.c
@@ -81,5 +81,5 @@ mbschr (const char *s, int c)
     }
   else
 #endif
-  return (strchr (s, c));
+  return (char *) strchr (s, c);
 }
diff --git a/lib/sh/utf8.c b/lib/sh/utf8.c
index c5503301..2d1abf30 100644
--- a/lib/sh/utf8.c
+++ b/lib/sh/utf8.c
@@ -35,7 +35,7 @@ extern int locale_utf8locale;
 char *
 utf8_mbschr (const char *s, int c)
 {
-  return strchr (s, c);                /* for now */
+  return (char *) strchr (s, c);       /* for now */
 }
 
 int
diff --git a/pathexp.c b/pathexp.c
index 87c49bf3..dc0f375d 100644
--- a/pathexp.c
+++ b/pathexp.c
@@ -525,7 +525,7 @@ static int
 glob_name_is_acceptable (const char *name)
 {
   struct ign *p;
-  char *n;
+  const char *n;
   int flags;
 
   /* . and .. are never matched. We extend this to the terminal component of a
-- 
2.54.0