Subject: bug#9318: 23.3.50; The first call of encode-coding-region() returns wrong result

From: Kazuhiro Ito <[email-masked]>
Date: Thu, 25 Aug 2011 18:54:13 +0900

> > I think relocation of buffer may cause the problem.
> 
> Does that help?
> 
> diff --git a/src/coding.c b/src/coding.c
> index 65c8a76..f34a023 100644
> --- a/src/coding.c
> +++ b/src/coding.c
> @@ -915,8 +915,8 @@ record_conversion_result (struct coding_system *coding,
>      }
>  }
> 
> -/* This wrapper macro is used to preserve validity of pointers into
> -   buffer text across calls to decode_char, which could cause
> +/* These wrapper macros are used to preserve validity of pointers into
> +   buffer text across calls to decode_char/encode_char, which could cause
>     relocation of buffers if it loads a charset map, because loading a
>     charset map allocates large structures.  */
>  #define CODING_DECODE_CHAR(coding, src, src_base, src_end, charset, code, c) \
> @@ -935,6 +935,21 @@ record_conversion_result (struct coding_system *coding,
>  	src_end += offset;						     \
>        }									     \
>    } while (0)
> +#define CODING_ENCODE_CHAR(coding, dst, dst_end, charset, c, code)	\
> +  do {									\
> +    charset_map_loaded = 0;						\
> +    code = ENCODE_CHAR (charset, c);					\
> +    if (charset_map_loaded)						\
> +      {									\
> +	const unsigned char *orig = coding->destination;		\
> +	EMACS_INT offset;						\
> +									\
> +	coding_set_destination (coding);				\
> +	offset = coding->destination - orig;				\
> +	dst += offset;							\
> +	dst_end += offset;						\
> +      }									\
> +  } while (0)
> 
> 
>  /* If there are at least BYTES length of room at dst, allocate memory
> @@ -2652,7 +2667,7 @@ encode_coding_emacs_mule (struct coding_system *coding)
>  	    {
>  	      charset = CHARSET_FROM_ID (preferred_charset_id);
>  	      if (CHAR_CHARSET_P (c, charset))
> -		code = ENCODE_CHAR (charset, c);
> +		CODING_ENCODE_CHAR (coding, dst, dst_end, charset, c, code);
>  	      else
>  		charset = char_charset (c, charset_list, &code);
>  	    }
> @@ -4185,7 +4200,8 @@ decode_coding_iso_2022 (struct coding_system *coding)
 
>  #define ENCODE_ISO_CHARACTER(charset, c)				   \
>    do {									   \
> -    int code = ENCODE_CHAR ((charset), (c));				   \
> +    int code;								   \
> +    CODING_ENCODE_CHAR (coding, dst, dst_end, charset, c, code);	   \
>  									   \
>      if (CHARSET_DIMENSION (charset) == 1)				   \
>        ENCODE_ISO_CHARACTER_DIMENSION1 ((charset), code);		   \

Andreas' patch resolved the problem partially.  It resolved the problem on
NetBSD with '-O0' CFLAGS, but failed on NetBSD with '-O2' and Windows.

I confirmed that adding the protection of coding->dst_object to
Andreas' patch resolved the problem on NetBSD with '-O2' but not on
Windows.  I don't know whether it is incorrect way or is not enough.

--- src/coding.c	2011-07-01 11:03:55 +0000
+++ src/coding.c	2011-08-24 23:39:49 +0000
@@ -7397,10 +7436,15 @@
       setup_ccl_program (&cclspec.ccl, CODING_CCL_ENCODER (coding));
     }
   do {
+    struct gcpro gcpro1;
+    GCPRO1 (coding->dst_object);
+
     coding_set_source (coding);
     consume_chars (coding, translation_table, max_lookup);
     coding_set_destination (coding);
     (*(coding->encoder)) (coding);
+
+    UNGCPRO;
   } while (coding->consumed_char < coding->src_chars);
 
   if (BUFFERP (coding->dst_object) && coding->produced_char > 0)

-- 
Kazuhiro Ito