|| (coding)->common_flags & CODING_REQUIRE_DECODING_MASK)
/* Return 1 if the coding system CODING requires code conversion on
- encoding. */
+ encoding.
+ The non-multibyte part of the condition is to support encoding of
+ unibyte strings/buffers generated by string-as-unibyte or
+ (set-buffer-multibyte nil) from multibyte strings/buffers. */
#define CODING_REQUIRE_ENCODING(coding) \
((coding)->src_multibyte \
|| (coding)->common_flags & CODING_REQUIRE_ENCODING_MASK)