Port to glibc 2.43+ with GCC 15+

Port to planned glibc 2.43 (scheduled for February 2026),
which will support qualifier-generic standard functions; see:
https://sourceware.org/git/?p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690
For example, strchr (P, C) will return pointer to const if P is
pointer to const.  The idea is to catch dumb programming errors when a
program mistakenly uses strchr to convert a pointer to const
to an unrestricted pointer.  This feature is required by C23,
and will be enabled by default in GCC 15.
* src/callint.c (Fcall_interactively):
Respect constness of pointer when calling memchr.
* src/gtkutil.c (xg_get_font):
2nd arg is char *, not const char *.
* src/xfaces.c (parse_float_color_comp): Return bool, not double.
New arg DST.  All callers changed.  This makes it easier for
callers to use char const *.
(parse_color_spec): Respect constness of pointer when calling strchr.

src/callint.c

@@ -450,7 +450,7 @@ invoke it (via an `interactive' spec that contains, for instance, an
   char const *tem = string;
   for (ptrdiff_t i = 2; tem < string_end; i++)
     {
-      char *pnl = memchr (tem + 1, '\n', string_len - (tem + 1 - string));
+      char const *pnl = memchr (tem + 1, '\n', string_len - (tem + 1 - string));
       ptrdiff_t sz = pnl ? pnl - (tem + 1) : string_end - (tem + 1);
 
       visargs[1] = make_string (tem + 1, sz);

src/gtkutil.c

@@ -2894,10 +2894,11 @@ xg_font_filter (const PangoFontFamily *family,
    `FAMILY [VALUE1 VALUE2] SIZE'
 
    This can be parsed using font_parse_fcname in font.c.
-   DEFAULT_NAME, if non-zero, is the default font name.  */
+   DEFAULT_NAME, if non-null, is the default font name;
+   it might be updated in place.  */
 
 Lisp_Object
-xg_get_font (struct frame *f, const char *default_name)
+xg_get_font (struct frame *f, char *default_name)
 {
   GtkWidget *w;
   int done = 0;

src/gtkutil.h

@@ -91,7 +91,7 @@ extern char *xg_get_file_name (struct frame *f,
                                bool mustmatch_p,
                                bool only_dir_p);
 
-extern Lisp_Object xg_get_font (struct frame *f, const char *);
+extern Lisp_Object xg_get_font (struct frame *f, char *);
 
 extern GtkWidget *xg_create_widget (const char *type,
                                     const char *name,

src/xfaces.c

@@ -950,19 +950,25 @@ parse_hex_color_comp (const char *s, const char *e, unsigned short *dst)
 }
 
 /* Parse floating-point color component specification that starts at S
-   and ends right before E.  Return the parsed number if in the range
-   [0,1]; otherwise return -1.  */
-static double
-parse_float_color_comp (const char *s, const char *e)
+   and ends right before E.  Put the integer near-equivalent of that
+   into *DST.  Return true if successful, false otherwise.  */
+static bool
+parse_float_color_comp (const char *s, const char *e, unsigned short *dst)
 {
   /* Only allow decimal float literals without whitespace.  */
   for (const char *p = s; p < e; p++)
     if (!((*p >= '0' && *p <= '9')
 	  || *p == '.' || *p == '+' || *p == '-' || *p == 'e' || *p == 'E'))
-      return -1;
+      return false;
   char *end;
   double x = strtod (s, &end);
-  return (end == e && x >= 0 && x <= 1) ? x : -1;
+  if (end == e && 0 <= x && x <= 1)
+    {
+      *dst = lrint (x * 65535);
+      return true;
+    }
+  else
+    return false;
 }
 
 /* Parse SPEC as a numeric color specification and set *R, *G and *B.
@@ -997,28 +1003,25 @@ parse_color_spec (const char *spec,
     }
   else if (strncmp (spec, "rgb:", 4) == 0)
     {
-      char *sep1, *sep2;
-      return ((sep1 = strchr (spec + 4, '/')) != NULL
-              && (sep2 = strchr (sep1 + 1, '/')) != NULL
+      char const *sep1 = strchr (spec + 4, '/');
+      if (!sep1)
+	return false;
+      char const *sep2 = strchr (sep1 + 1, '/');
+      return (sep2
               && parse_hex_color_comp (spec + 4, sep1, r)
               && parse_hex_color_comp (sep1 + 1, sep2, g)
               && parse_hex_color_comp (sep2 + 1, spec + len, b));
     }
   else if (strncmp (spec, "rgbi:", 5) == 0)
     {
-      char *sep1, *sep2;
-      double red, green, blue;
-      if ((sep1 = strchr (spec + 5, '/')) != NULL
-          && (sep2 = strchr (sep1 + 1, '/')) != NULL
-          && (red = parse_float_color_comp (spec + 5, sep1)) >= 0
-          && (green = parse_float_color_comp (sep1 + 1, sep2)) >= 0
-          && (blue = parse_float_color_comp (sep2 + 1, spec + len)) >= 0)
-        {
-          *r = lrint (red * 65535);
-          *g = lrint (green * 65535);
-          *b = lrint (blue * 65535);
-          return true;
-        }
+      char const *sep1 = strchr (spec + 5, '/');
+      if (!sep1)
+	return false;
+      char const *sep2 = strchr (sep1 + 1, '/');
+      return (sep2
+	      && parse_float_color_comp (spec + 5, sep1, r)
+	      && parse_float_color_comp (sep1 + 1, sep2, g)
+	      && parse_float_color_comp (sep2 + 1, spec + len, b));
     }
   return false;
 }