Fix byte-counting error in ‘format’

Problem reported by Paul Pogonyshev (Bug#38191).
* src/editfns.c (styled_format): When checking for adjacent
%-sequences, use byte position rather than character position.
* test/src/editfns-tests.el (format-properties): Test for fix.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 1b33f397110..8fc866d391f 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -3143,7 +3143,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
     /* The start and end bytepos in the output string.  */
     ptrdiff_t start, end;
 
-    /* The start of the spec in the format string.  */
+    /* The start bytepos of the spec in the format string.  */
     ptrdiff_t fbeg;
 
     /* Whether the argument is a string with intervals.  */
@@ -3954,7 +3954,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
                     {
                       position++;
                       if (fieldn < nspec
-                          && position > info[fieldn].fbeg
+                          && bytepos >= info[fieldn].fbeg
                           && translated == info[fieldn].start)
                         {
                           translated += info[fieldn].end - info[fieldn].start;
@@ -3976,7 +3976,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
                     {
                       position++;
                       if (fieldn < nspec
-                          && position > info[fieldn].fbeg
+                          && bytepos >= info[fieldn].fbeg
                           && translated == info[fieldn].start)
                         {
                           translated += info[fieldn].end - info[fieldn].start;