master d52d6e1e10: Avoid assertion violations in STRING_CHAR

[Eli Zaretskii]

branch: master
commit d52d6e1e106117eb4bba81a65e256e2e793037b6
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Avoid assertion violations in STRING_CHAR
    
    * src/xdisp.c (handle_composition_prop):
    * src/editfns.c (styled_format): Don't call 'STRING_CHAR' on
    unibyte strings.  This avoids assertion violation in
    'string_char_and_length'.
---
 src/editfns.c | 4 +++-
 src/xdisp.c   | 5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/editfns.c b/src/editfns.c
index b774e79337..c1414071c7 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -3552,7 +3552,9 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool 
message)
                      || conversion == 'o' || conversion == 'x'
                      || conversion == 'X'))
            error ("Invalid format operation %%%c",
-                  STRING_CHAR ((unsigned char *) format - 1));
+                  multibyte_format
+                  ? STRING_CHAR ((unsigned char *) format - 1)
+                  : *((unsigned char *) format - 1));
          else if (! (FIXNUMP (arg) || ((BIGNUMP (arg) || FLOATP (arg))
                                        && conversion != 'c')))
            error ("Format specifier doesn't match argument type");
diff --git a/src/xdisp.c b/src/xdisp.c
index 818cf5e3f8..9534e27843 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -6312,7 +6312,10 @@ handle_composition_prop (struct it *it)
       pos_byte = IT_STRING_BYTEPOS (*it);
       string = it->string;
       s = SDATA (string) + pos_byte;
-      it->c = STRING_CHAR (s);
+      if (STRING_MULTIBYTE (string))
+       it->c = STRING_CHAR (s);
+      else
+       it->c = *s;
     }
   else
     {