Make STRING_SET_MULTIBYTE an inline function

* src/lisp.h (STRING_SET_MULTIBYTE): Make it into a function.

* src/composite.c (Fcomposition_get_gstring):
Prefer `make_multibyte_string` over Fconcat+STRING_SET_MULTIBYTE.

2 files changed, 13 insertions, 11 deletions

diff --git a/src/composite.c b/src/composite.c
index 4d69702171f..552214ae848 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -1871,7 +1871,8 @@ should be ignored.  */)
   else
     {
       CHECK_STRING (string);
-      validate_subarray (string, from, to, SCHARS (string), &frompos, &topos);
+      ptrdiff_t chars = SCHARS (string);
+      validate_subarray (string, from, to, chars, &frompos, &topos);
       if (! STRING_MULTIBYTE (string))
         {
           ptrdiff_t i;
@@ -1881,9 +1882,10 @@ should be ignored.  */)
               error ("Attempt to shape unibyte text");
           /* STRING is a pure-ASCII string, so we can convert it (or,
              rather, its copy) to multibyte and use that thereafter.  */
-          Lisp_Object string_copy = Fconcat (1, &string);
-          STRING_SET_MULTIBYTE (string_copy);
-          string = string_copy;
+          /* FIXME: Not clear why we need to do that: AFAICT the rest of
+             the code should work on an ASCII-only unibyte string just
+             as well (bug#56347).  */
+          string = make_multibyte_string (SDATA (string), chars, chars);
         }
       frombyte = string_char_to_byte (string, frompos);
     }
diff --git a/src/lisp.h b/src/lisp.h
index 5ffc2bb0386..dc496cc1658 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1640,13 +1640,13 @@ STRING_MULTIBYTE (Lisp_Object str)
 
 /* Mark STR as a multibyte string.  Assure that STR contains only
    ASCII characters in advance.  */
-#define STRING_SET_MULTIBYTE(STR)                       \
-  do {                                                  \
-    if (XSTRING (STR)->u.s.size == 0)                   \
-      (STR) = empty_multibyte_string;                   \
-    else                                                \
-      XSTRING (STR)->u.s.size_byte = XSTRING (STR)->u.s.size; \
-  } while (false)
+INLINE void
+STRING_SET_MULTIBYTE (Lisp_Object str)
+{
+  /* The 0-length strings are unique&shared so we can't modify them.  */
+  eassert (XSTRING (str)->u.s.size > 0);
+  XSTRING (str)->u.s.size_byte = XSTRING (str)->u.s.size;
+}
 
 /* Convenience functions for dealing with Lisp strings.  */