[Rd] Invalid UTF-8 with gsub(perl=TRUE) and iconv(sub="")

[Prof Brian Ripley]

On 09/09/2013 09:49, Milan Bouchet-Valat wrote:
> Hi!
>
> I experience an error with an invalid UTF-8 character passed to
> gsub(..., perl=TRUE); the interesting point is that with perl=FALSE (the
> default) no error happens. (The character itself was read from an
> invalid HTML file.) Illustration of the error:
>
> gsub("a", "", "\U3e3965", perl=FALSE)
> # [1] "\U3e3965"
> gsub("a", "", "\U3e3965", perl=TRUE)
> # Error in gsub("a", "", "\U3e3965", perl = TRUE) :
> #   input string 1 is invalid UTF-8
>
>
> The error message in the second command seems to come from
> src/main/grep.c:1640 (in do_gsub):
> if (!utf8Valid(s)) error(("input string %d is invalid UTF-8"), i+1);
>
> utf8Valid() relies on valid_utf8() from PCRE, whose behavior is
> described in src/extra/pcre/pcre_valid_utf8.c.
>
>
>
> Even more problematic/interesting is the fact that iconv() does not
> consider the above character as invalid, as it does not replace it when
> using the sub argument.
>> iconv("a\U3e3965", sub="")
> [1] "a\U003e3965"
>
> On the contrary, an invalid sequence such as \xff is substituted:
> iconv("a\xff", sub="")
> # [1] "a"
>
> This makes it difficult to sanitize the string before passing it to
> gsub(perl=TRUE). Thus, I'm wondering whether something could be done,
> and where. Should iconv() and PCRE be made to agree on the definition of
> an invalid UTF-8 sequence?

iconv() is using a system service: read its help page.  So you know 
where to report this ....


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595