Fix ‘format’ bug with property offsets

* src/editfns.c (styled_format): Fix recently-introduced ‘format’
bug in calculating string property offsets (Bug#21351).

1 files changed, 6 insertions, 2 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 9db4d9328a0..bbb139f2980 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -4013,10 +4013,14 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
             error ("Format string ends in middle of format specifier");
 
           memset (&discarded[format0 - format_start], 1, format - format0);
-          conversion = *format++;
+          conversion = *format;
           if (conversion == '%')
-            goto copy_char;
+            {
+              format++;
+              goto copy_char;
+            }
           discarded[format - format_start] = 1;
+          format++;
 
           ++n;
           if (! (n < nargs))