[PATCH v2 2/3] libcpp: add a function to determine UTF-8 validity of a C string

[Jason Merrill]

On 10/27/22 13:16, Ben Boeckel wrote:
> This simplifies the interface for other UTF-8 validity detections when a
> simple "yes" or "no" answer is sufficient.
> 
> Signed-off-by: Ben Boeckel <ben.boeckel@kitware.com>
> ---
>   libcpp/ChangeLog  |  6 ++++++
>   libcpp/charset.cc | 18 ++++++++++++++++++
>   libcpp/internal.h |  2 ++
>   3 files changed, 26 insertions(+)
> 
> diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
> index 4d707277531..4e2c7900ae2 100644
> --- a/libcpp/ChangeLog
> +++ b/libcpp/ChangeLog
> @@ -1,3 +1,9 @@
> +2022-10-27  Ben Boeckel  <ben.boeckel@kitware.com>
> +
> +	* include/charset.cc: Add `_cpp_valid_utf8_str` which determines
> +	whether a C string is valid UTF-8 or not.
> +	* include/internal.h: Add prototype for `_cpp_valid_utf8_str`.
> +
>   2022-10-27  Ben Boeckel  <ben.boeckel@kitware.com>
>   
>   	* include/charset.cc: Reject encodings of codepoints above 0x10FFFF.
> diff --git a/libcpp/charset.cc b/libcpp/charset.cc
> index e9da6674b5f..0524ab6beba 100644
> --- a/libcpp/charset.cc
> +++ b/libcpp/charset.cc
> @@ -1864,6 +1864,24 @@ _cpp_valid_utf8 (cpp_reader *pfile,
>     return true;
>   }

Please add a comment before the function.

> +extern bool
> +_cpp_valid_utf8_str (const char *name)
> +{
> +  const uchar* in = (const uchar*)name;
> +  size_t len = strlen(name);
> +  cppchar_t cp;
> +
> +  while (*in)
> +    {
> +      if (one_utf8_to_cppchar(&in, &len, &cp))
> +	{
> +	  return false;
> +	}
> +    }

We usually omit unnecessary { } around single statements.

> +  return true;
> +}
> +
>   /* Subroutine of convert_hex and convert_oct.  N is the representation
>      in the execution character set of a numeric escape; write it into the
>      string buffer TBUF and update the end-of-string pointer therein.  WIDE
> diff --git a/libcpp/internal.h b/libcpp/internal.h
> index badfd1b40da..4f2dd4a2f5c 100644
> --- a/libcpp/internal.h
> +++ b/libcpp/internal.h
> @@ -834,6 +834,8 @@ extern bool _cpp_valid_utf8 (cpp_reader *pfile,
>   			     struct normalize_state *nst,
>   			     cppchar_t *cp);
>   
> +extern bool _cpp_valid_utf8_str (const char *str);
> +
>   extern void _cpp_destroy_iconv (cpp_reader *);
>   extern unsigned char *_cpp_convert_input (cpp_reader *, const char *,
>   					  unsigned char *, size_t, size_t,