[4/5] locale: localdef input files are now encoded in UTF-8

  Previously, they were assumed to be in ISO-8859-1, and that the output
charset overlapped with ISO-8859-1 for the characters actually used.
However, this did not work as intended on many architectures even for
an ISO-8859-1 output encoding because of the char signedness bug in
lr_getc.  Therefore, this commit switches to UTF-8 without making
provisions for backwards compatibility.

The following Elisp code can be used to convert locale definition files
to UTF-8:

(defun glibc/convert-localedef (from to)
  (interactive "r")
  (save-excursion
    (save-restriction
      (narrow-to-region from to)
      (goto-char (point-min))
      (save-match-data
	(while (re-search-forward "<U\\([0-9a-fA-F]+\\)>" nil t)
	  (let* ((codepoint (string-to-number (match-string 1) 16))
		 (converted
		  (cond
		   ((memq codepoint '(?/ ?\ ?< ?>))
		    (string ?/ codepoint))
		   ((= codepoint ?\") "<U0022>")
		   (t (string codepoint)))))
	    (replace-match converted t)))))))
---
 NEWS                         |   4 +
 locale/programs/linereader.c | 144 ++++++++++++++++++++++++++++++++---
 2 files changed, 137 insertions(+), 11 deletions(-)
  

On 5/19/22 17:06, Florian Weimer via Libc-alpha wrote:
> Previously, they were assumed to be in ISO-8859-1, and that the output
> charset overlapped with ISO-8859-1 for the characters actually used.
> However, this did not work as intended on many architectures even for
> an ISO-8859-1 output encoding because of the char signedness bug in
> lr_getc.  Therefore, this commit switches to UTF-8 without making
> provisions for backwards compatibility.

That sounds acceptable to me.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

> 
> The following Elisp code can be used to convert locale definition files
> to UTF-8:
> 
> (defun glibc/convert-localedef (from to)
>   (interactive "r")
>   (save-excursion
>     (save-restriction
>       (narrow-to-region from to)
>       (goto-char (point-min))
>       (save-match-data
> 	(while (re-search-forward "<U\\([0-9a-fA-F]+\\)>" nil t)
> 	  (let* ((codepoint (string-to-number (match-string 1) 16))
> 		 (converted
> 		  (cond
> 		   ((memq codepoint '(?/ ?\ ?< ?>))
> 		    (string ?/ codepoint))
> 		   ((= codepoint ?\") "<U0022>")
> 		   (t (string codepoint)))))
> 	    (replace-match converted t)))))))

OK.

> ---
>  NEWS                         |   4 +
>  locale/programs/linereader.c | 144 ++++++++++++++++++++++++++++++++---
>  2 files changed, 137 insertions(+), 11 deletions(-)
> 
> diff --git a/NEWS b/NEWS
> index ad0c08d8ca..7ce0d8a135 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -20,6 +20,10 @@ Major new features:
>    have been added.  The pidfd functionality provides access to a process
>    while avoiding the issue of PID reuse on tranditional Unix systems.
>  
> +* localedef now accepts locale definition files encoded in UTF-8.
> +  Previously, input bytes not within the ASCII range resulted in
> +  unpredictable output.

OK.

> +
>  Deprecated and removed features, and other changes affecting compatibility:
>  
>  * Support for prelink will be removed in the next release; this includes
> diff --git a/locale/programs/linereader.c b/locale/programs/linereader.c
> index f7292f0102..b484327969 100644
> --- a/locale/programs/linereader.c
> +++ b/locale/programs/linereader.c
> @@ -42,6 +42,7 @@ static struct token *get_string (struct linereader *lr,
>  				 struct localedef_t *locale,
>  				 const struct repertoire_t *repertoire,
>  				 int verbose);
> +static bool utf8_decode (struct linereader *lr, uint8_t ch1, uint32_t *wch);

OK.

>  
>  
>  struct linereader *
> @@ -327,6 +328,17 @@ lr_token (struct linereader *lr, const struct charmap_t *charmap,
>  	}
>        lr_ungetn (lr, 2);
>        break;
> +
> +    case 0x80 ... 0xff:		/* UTF-8 sequence.  */
> +      uint32_t wch;
> +      if (!utf8_decode (lr, ch, &wch))
> +	{
> +	  lr->token.tok = tok_error;
> +	  return &lr->token;
> +	}
> +      lr->token.tok = tok_ucs4;
> +      lr->token.val.ucs4 = wch;
> +      return &lr->token;

OK.

>      }
>  
>    return get_ident (lr);
> @@ -673,6 +685,87 @@ translate_unicode_codepoint (struct localedef_t *locale,
>      return false;
>  }
>  
> +/* Returns true if ch is not EOF (that is, non-negative) and a valid
> +   UTF-8 trailing byte.  */
> +static bool
> +utf8_valid_trailing (int ch)
> +{
> +  return ch >= 0 && (ch & 0xc0) == 0x80;
> +}

OK.

> +
> +/* Reports an error for a broken UTF-8 sequence.  CH2 to CH4 may be
> +   EOF.  Always returns false.  */
> +static bool
> +utf8_sequence_error (struct linereader *lr, uint8_t ch1, int ch2, int ch3,
> +		     int ch4)
> +{
> +  char buf[30];
> +
> +  if (ch2 < 0)
> +    snprintf (buf, sizeof (buf), "0x%02x", ch1);
> +  else if (ch3 < 0)
> +    snprintf (buf, sizeof (buf), "0x%02x 0x%02x", ch1, ch2);
> +  else if (ch4 < 0)
> +    snprintf (buf, sizeof (buf), "0x%02x 0x%02x 0x%02x", ch1, ch2, ch3);
> +  else
> +    snprintf (buf, sizeof (buf), "0x%02x 0x%02x 0x%02x 0x%02x",
> +	      ch1, ch2, ch3, ch4);
> +
> +  lr_error (lr, _("invalid UTF-8 sequence %s"), buf);
> +  return false;

OK.

> +}
> +
> +/* Reads a UTF-8 sequence from LR, with the leading byte CH1, and
> +   stores the decoded codepoint in *WCH.  Returns false on failure and
> +   reports an error.  */
> +static bool
> +utf8_decode (struct linereader *lr, uint8_t ch1, uint32_t *wch)
> +{
> +  /* See RFC 3629 section 4 and __gconv_transform_utf8_internal.  */
> +  if (ch1 < 0xc2)
> +    return utf8_sequence_error (lr, ch1, -1, -1, -1);

OK. While ASCII goes to 7F the standard says ch2 would be > c2, so cover the whole range here.

> +
> +  int ch2 = lr_getc (lr);
> +  if (!utf8_valid_trailing (ch2))
> +    return utf8_sequence_error (lr, ch1, ch2, -1, -1);
> +
> +  if (ch1 <= 0xdf)
> +    {
> +      uint32_t result = ((ch1 & 0x1f)  << 6) | (ch2 & 0x3f);
> +      if (result < 0x80)
> +	return utf8_sequence_error (lr, ch1, ch2, -1, -1);
> +      *wch = result;
> +      return true;
> +    }

OK.

> +
> +  int ch3 = lr_getc (lr);
> +  if (!utf8_valid_trailing (ch3) || ch1 < 0xe0)
> +    return utf8_sequence_error (lr, ch1, ch2, ch3, -1);
> +
> +  if (ch1 <= 0xef)
> +    {
> +      uint32_t result = (((ch1 & 0x0f)  << 12)
> +			 | ((ch2 & 0x3f) << 6)
> +			 | (ch3 & 0x3f));
> +      if (result < 0x800)
> +	return utf8_sequence_error (lr, ch1, ch2, ch3, -1);
> +      *wch = result;
> +      return true;
> +    }
> +
> +  int ch4 = lr_getc (lr);
> +  if (!utf8_valid_trailing (ch4) || ch1 < 0xf0 || ch1 > 0xf4)
> +    return utf8_sequence_error (lr, ch1, ch2, ch3, ch4);
> +
> +  uint32_t result = (((ch1 & 0x07)  << 18)
> +		     | ((ch2 & 0x3f) << 12)
> +		     | ((ch3 & 0x3f) << 6)
> +		     | (ch4 & 0x3f));
> +  if (result < 0x10000)
> +    return utf8_sequence_error (lr, ch1, ch2, ch3, ch4);
> +  *wch = result;
> +  return true;
> +}

OK.

>  
>  static struct token *
>  get_string (struct linereader *lr, const struct charmap_t *charmap,
> @@ -696,7 +789,11 @@ get_string (struct linereader *lr, const struct charmap_t *charmap,
>  
>        buf2 = NULL;
>        while ((ch = lr_getc (lr)) != '"' && ch != '\n' && ch != EOF)
> -	addc (&lrb, ch);
> +	{
> +	  if (ch >= 0x80)
> +	    lr_error (lr, _("illegal 8-bit character in untranslated string"));
> +	  addc (&lrb, ch);
> +	}

OK.

>  
>        /* Catch errors with trailing escape character.  */
>        if (lrb.act > 0 && lrb.buf[lrb.act - 1] == lr->escape_char
> @@ -730,24 +827,49 @@ get_string (struct linereader *lr, const struct charmap_t *charmap,
>  
>  	  if (ch != '<')
>  	    {
> -	      /* The standards leave it up to the implementation to decide
> -		 what to do with character which stand for themself.  We
> -		 could jump through hoops to find out the value relative to
> -		 the charmap and the repertoire map, but instead we leave
> -		 it up to the locale definition author to write a better
> -		 definition.  We assume here that every character which
> -		 stands for itself is encoded using ISO 8859-1.  Using the
> -		 escape character is allowed.  */
> +	      /* The standards leave it up to the implementation to
> +		 decide what to do with characters which stand for
> +		 themselves.  This implementation treats the input
> +		 file as encoded in UTF-8.  */

OK. This is the right direction.

>  	      if (ch == lr->escape_char)
>  		{
>  		  ch = lr_getc (lr);
> +		  if (ch >= 0x80)
> +		    {
> +		      lr_error (lr, _("illegal 8-bit escape sequence"));
> +		      illegal_string = true;
> +		      break;
> +		    }

OK.

>  		  if (ch == '\n' || ch == EOF)
>  		    break;
> +		  addc (&lrb, ch);
> +		  wch = ch;
> +		}
> +	      else if (ch < 0x80)
> +		{
> +		  wch = ch;
> +		  addc (&lrb, ch);
> +		}
> +	      else 		/* UTF-8 sequence.  */
> +		{
> +		  if (!utf8_decode (lr, ch, &wch))
> +		    {
> +		      illegal_string = true;
> +		      break;
> +		    }
> +		  if (!translate_unicode_codepoint (locale, charmap,
> +						    repertoire, wch, &lrb))
> +		    {
> +		      /* Ignore the rest of the string.  Callers may
> +			 skip this string because it cannot be encoded
> +			 in the output character set.  */
> +		      illegal_string = true;
> +		      continue;
> +		    }
>  		}
>  
> -	      addc (&lrb, ch);
>  	      if (return_widestr)
> -		ADDWC ((uint32_t) ch);
> +		ADDWC (wch);
>  
>  	      continue;
>  	    }