* src/json.c (Fjson_insert): Don't temporarily insert invalid bytes in buffer

1 files changed, 8 insertions, 9 deletions

diff --git a/src/json.c b/src/json.c
index 607b8d32646..21c4b946b4e 100644
--- a/src/json.c
+++ b/src/json.c
@@ -739,9 +739,6 @@ usage: (json-insert OBJECT &rest ARGS)  */)
   ptrdiff_t inserted_bytes = data.inserted_bytes;
   if (inserted_bytes > 0)
     {
-      /* Make the inserted text part of the buffer, as unibyte text.  */
-      insert_from_gap_1 (inserted_bytes, inserted_bytes, false);
-
       /* If required, decode the stuff we've read into the gap.  */
       struct coding_system coding;
       /* JSON strings are UTF-8 encoded strings.  If for some reason
@@ -753,17 +750,19 @@ usage: (json-insert OBJECT &rest ARGS)  */)
         !NILP (BVAR (current_buffer, enable_multibyte_characters));
       if (CODING_MAY_REQUIRE_DECODING (&coding))
         {
-          move_gap_both (PT, PT_BYTE);
-          GAP_SIZE += inserted_bytes;
-          ZV_BYTE -= inserted_bytes;
-          Z_BYTE -= inserted_bytes;
-          ZV -= inserted_bytes;
-          Z -= inserted_bytes;
+          /* Now we have all the new bytes at the beginning of the gap,
+             but `decode_coding_gap` needs them at the end of the gap, so
+             we need to move them.  */
+          memmove (GAP_END_ADDR - inserted_bytes, GPT_ADDR, inserted_bytes);
           decode_coding_gap (&coding, inserted_bytes);
           inserted = coding.produced_char;
         }
       else
         {
+          /* Make the inserted text part of the buffer, as unibyte text.  */
+          eassert (NILP (BVAR (current_buffer, enable_multibyte_characters)));
+          insert_from_gap_1 (inserted_bytes, inserted_bytes, false);
+
           /* The target buffer is unibyte, so we don't need to decode.  */
           invalidate_buffer_caches (current_buffer,
                                     PT, PT + inserted_bytes);