On Thu, 12 Mar 2015 16:41:59 +0100
Ulrike Fischer
Am Thu, 12 Mar 2015 08:48:27 +0100 schrieb Manfred Lotz:
Hi all, If I run this minimal example
\starttext
�
\stopluacode
\stoptext
I get
tex error > error on line 3 in file /data/tmp/u1.tex: ! String contains an invalid utf-8 sequence
and some more lines.
The character above is:
Character: � Character name: REPLACEMENT CHARACTER Charblock: Specials Category: Other symbol Unicode: U+fffd UTF8: 0xefbfbd
which is a valid utf8 character.
Questions:
1. Why is it considered to be invalid?
This is not a context question/problem but related to the binary (you would get the same error with lualatex or plain)
Yes, I know.
The luatex code contains the lines (in unistring.w)
if (val == 0xFFFD) utf_error(); return (val);
in a function str2uni. I didn't really try to understand the code but it looks as if 0xFFFD is used as "invalid marker": If luatex encounters something that isn't valid utf8 it maps val to 0xFFFD and then test against 0xFFFD to rise an error.
Took me a while to find the repository but finally I got it.
2. Are there other valid utf8 characters which are considered invalid?
The comment in the code says
/* the 5- and 6-byte UTF-8 sequences generate integers
that are outside of the valid UCS range, and therefore
unsupported */
Well, it is called REPLACEMENT CHARACTER, and it seems that this character will be used to replace invalid characters. Then it causes if (val == 0xFFFD) utf_error(); the error message tex_error("String contains an invalid utf-8 sequence", hlp); to be displayed. Ok, this answers my question. Thanks for the pointer. -- Manfred