mruby-io: use mrb_int for mrb_hal_io_readlink() return type

int64_t was unnecessary; readlink(2) returns ssize_t (bounded by
PATH_MAX), and the Windows HAL just raises NotImplementedError.

Co-authored-by: Claude <noreply@anthropic.com>

mrbgems/hal-posix-io/src/io_hal.c

@@ -200,14 +200,11 @@ mrb_hal_io_symlink(mrb_state *mrb, const char *target, const char *linkpath)
   return symlink(target, linkpath);
 }
 
-int64_t
+mrb_int
 mrb_hal_io_readlink(mrb_state *mrb, const char *path, char *buf, size_t bufsize)
 {
-  ssize_t rc;
   (void)mrb;
-
-  rc = readlink(path, buf, bufsize);
-  return (int64_t)rc;
+  return (mrb_int)readlink(path, buf, bufsize);
 }
 
 char*

mrbgems/hal-win-io/src/io_hal.c

@@ -207,7 +207,7 @@ mrb_hal_io_symlink(mrb_state *mrb, const char *target, const char *linkpath)
   return -1;  /* not reached */
 }
 
-int64_t
+mrb_int
 mrb_hal_io_readlink(mrb_state *mrb, const char *path, char *buf, size_t bufsize)
 {
   (void)path;

mrbgems/mruby-io/include/io_hal.h

@@ -189,7 +189,7 @@ int mrb_hal_io_symlink(mrb_state *mrb, const char *target, const char *linkpath)
  * @param bufsize Buffer size
  * @return Number of bytes placed in buf, -1 on error (sets errno)
  */
-int64_t mrb_hal_io_readlink(mrb_state *mrb, const char *path, char *buf, size_t bufsize);
+mrb_int mrb_hal_io_readlink(mrb_state *mrb, const char *path, char *buf, size_t bufsize);
 
 /**
  * Resolve pathname to absolute path

mrbgems/mruby-io/src/file.c

@@ -900,7 +900,7 @@ mrb_file_s_readlink(mrb_state *mrb, mrb_value klass)
   /* Use mrb_temp_alloc for exception safety - GC will clean up on exception */
   char *buf = (char*)mrb_temp_alloc(mrb, PATH_MAX);
 
-  int64_t rc = mrb_hal_io_readlink(mrb, tmp, buf, PATH_MAX);
+  mrb_int rc = mrb_hal_io_readlink(mrb, tmp, buf, PATH_MAX);
   mrb_locale_free(tmp);
   if (rc == -1) {
     mrb_sys_fail(mrb, path);