Ensure empty strings are unique and pure

This showed up as differences in .elc files produced by this branch.

* src/alloc.c (init_strings): Ensure empty strings are pure.
(make_clear_multibyte_string): Return `empty_multibyte_string' when
asked for an empty string.

1 files changed, 5 insertions, 10 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 576850c0029..f67f32f7bc9 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1771,13 +1771,8 @@ static ptrdiff_t const STRING_BYTES_MAX =
 static void
 init_strings (void)
 {
-#ifdef HAVE_MPS
-  empty_multibyte_string = igc_make_multibyte_string (0, 0, false);
-  empty_unibyte_string = igc_make_unibyte_string (0, 0, false);
-#else
   empty_unibyte_string = make_pure_string ("", 0, 0, 0);
   empty_multibyte_string = make_pure_string ("", 0, 0, 1);
-#endif
   staticpro (&empty_unibyte_string);
   staticpro (&empty_multibyte_string);
 }
@@ -2631,17 +2626,17 @@ make_uninit_string (EMACS_INT length)
 static Lisp_Object
 make_clear_multibyte_string (EMACS_INT nchars, EMACS_INT nbytes, bool clearit)
 {
+  if (nchars < 0)
+    emacs_abort ();
+  if (!nbytes)
+    return empty_multibyte_string;
+
 #ifdef HAVE_MPS
   return igc_make_multibyte_string (nchars, nbytes, clearit);
 #else
   Lisp_Object string;
   struct Lisp_String *s;
 
-  if (nchars < 0)
-    emacs_abort ();
-  if (!nbytes)
-    return empty_multibyte_string;
-
   s = allocate_string ();
   s->u.s.intervals = NULL;
   allocate_string_data (s, nchars, nbytes, clearit, false);