Subject: bug#46933: Possible bugs in filepos-to-bufferpos / bufferpos-to-filepos

From: handa <[email-masked]>
Date: Sat, 27 Mar 2021 14:38:56 +0900

In article <[email-masked]>, Eli Zaretskii <[email-masked]> writes:

> Kenichi, why are these 6 bytes inserted by encode-coding-region, but
> not when we encode the same text as part of saving the buffer to its
> file?  And why does it happen near the end of the text, between those
> 2 particular letters?

There surely exists a bug.  Could you please try the attached patch?

The reason why that bug did not happen on file writing is that the code
in write_region calls encoding routine repeatedly without
CODING_MODE_LAST_BLOCK flag, and only in the case that flushing is
required (e.g. the case of iso-2022-jp), just for flushing, it calls
enoding routine again with CODING_MODE_LAST_BLOCK flag.  In that case,
carryover does not happen in encode_coding ().

---
K. Handa
[email-masked]

diff --git a/src/coding.c b/src/coding.c
index 221a9cad89..a9d5a7ccdc 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -7799,7 +7799,14 @@ encode_coding (struct coding_system *coding)
     coding_set_source (coding);
     consume_chars (coding, translation_table, max_lookup);
     coding_set_destination (coding);
+    /* If consume_chars did not consume all source chars, we call
+       coding->encoder again in the next iteration, and thus, for this
+       iteration, we must clear CODING_MODE_LAST_BLOCK flag.  */
+    unsigned saved_mode = coding->mode;
+    if (coding->consumed_char < coding->src_chars)
+      coding->mode &= ~CODING_MODE_LAST_BLOCK;
     (*(coding->encoder)) (coding);
+    coding->mode = saved_mode;
   } while (coding->consumed_char < coding->src_chars);
 
   if (BUFFERP (coding->dst_object) && coding->produced_char > 0)