[PATCH v2 1/3] libcpp: reject codepoints above 0x10FFFF

[Jason Merrill]

On 10/27/22 13:16, Ben Boeckel wrote:
> Unicode does not support such values because they are unrepresentable in
> UTF-16.
> 
> Signed-off-by: Ben Boeckel <ben.boeckel@kitware.com>
> ---
>   libcpp/ChangeLog  | 6 ++++++
>   libcpp/charset.cc | 4 ++--
>   2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
> index 18d5bcceaf0..4d707277531 100644
> --- a/libcpp/ChangeLog
> +++ b/libcpp/ChangeLog
> @@ -1,3 +1,9 @@
> +2022-10-27  Ben Boeckel  <ben.boeckel@kitware.com>
> +
> +	* include/charset.cc: Reject encodings of codepoints above 0x10FFFF.
> +	UTF-16 does not support such codepoints and therefore all Unicode
> +	rejects such values.
> +
>   2022-10-19  Lewis Hyatt  <lhyatt@gmail.com>
>   
>   	* include/cpplib.h (struct cpp_string): Use new "string_length" GTY.
> diff --git a/libcpp/charset.cc b/libcpp/charset.cc
> index 12a398e7527..e9da6674b5f 100644
> --- a/libcpp/charset.cc
> +++ b/libcpp/charset.cc
> @@ -216,7 +216,7 @@ one_utf8_to_cppchar (const uchar **inbufp, size_t *inbytesleftp,
>     if (c <= 0x3FFFFFF && nbytes > 5) return EILSEQ;
>   
>     /* Make sure the character is valid.  */
> -  if (c > 0x7FFFFFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ;
> +  if (c > 0x10FFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ;

Please also adjust the comment before the function that talks about the 
0x7FFFFFFF maximum.

>   
>     *cp = c;
>     *inbufp = inbuf;
> @@ -320,7 +320,7 @@ one_utf32_to_utf8 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,
>     s += inbuf[bigend ? 2 : 1] << 8;
>     s += inbuf[bigend ? 3 : 0];
>   
> -  if (s >= 0x7FFFFFFF || (s >= 0xD800 && s <= 0xDFFF))
> +  if (s > 0x10FFFF || (s >= 0xD800 && s <= 0xDFFF))
>       return EILSEQ;
>   
>     rval = one_cppchar_to_utf8 (s, outbufp, outbytesleftp);