Re: [PATCHv2 4/5] gdb: Introduce new language field la_is_string_type_p

[Tom Tromey <tom at tromey dot com>]

>>>>> "Andrew" == Andrew Burgess <andrew.burgess@embecosm.com> writes:

Andrew> Some languages already have a "is this a string" predicate that I was
Andrew> able to reuse, while for other languages I've had to add a new
Andrew> predicate.  In this case I took inspiration from the value printing
Andrew> code for that language - what different conditions would result in
Andrew> printing something as a string.

This looks essentially fine, but I had some questions.

Andrew> +bool
Andrew> +c_is_string_type_p (struct type *type)
Andrew> +{
Andrew> +  type = check_typedef (type);
Andrew> +  while (TYPE_CODE (type) == TYPE_CODE_REF)
Andrew> +    {
Andrew> +      type = TYPE_TARGET_TYPE (type);
Andrew> +      type = check_typedef (type);
Andrew> +    }
Andrew> +
Andrew> +  switch (TYPE_CODE (type))
Andrew> +    {
Andrew> +    case TYPE_CODE_ARRAY:
Andrew> +      {
Andrew> +	/* See if target type looks like a string.  */
Andrew> +	struct type *array_target_type = TYPE_TARGET_TYPE (type);
Andrew> +	return (TYPE_LENGTH (type) > 0
Andrew> +		&& TYPE_LENGTH (array_target_type) > 0
Andrew> +		&& c_textual_element_type (array_target_type, 0));
Andrew> +      }
Andrew> +    case TYPE_CODE_STRING:
Andrew> +      return true;

It seems to me that a "char *" should be considered a string in C;
and probably a "wchar_t *" as well.  Maybe see c-lang.c:classify_type.

Andrew> +/* Return true if TYPE is a string type.  */
Andrew> +static bool
Andrew> +rust_is_string_type_p (struct type *type)
Andrew> +{
Andrew> +  LONGEST low_bound, high_bound;
Andrew> +
Andrew> +  type = check_typedef (type);
Andrew> +  return ((TYPE_CODE (type) == TYPE_CODE_STRING)
Andrew> +	  || (TYPE_CODE (type) == TYPE_CODE_PTR
Andrew> +	      && (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_ARRAY
Andrew> +		  && rust_u8_type_p (TYPE_TARGET_TYPE (TYPE_TARGET_TYPE (type)))
Andrew> +		  && get_array_bounds (TYPE_TARGET_TYPE (type), &low_bound,
Andrew> +				       &high_bound)))
Andrew> +	  || ((TYPE_CODE (type) == TYPE_CODE_UNION
Andrew> +	       || (TYPE_CODE (type) == TYPE_CODE_STRUCT
Andrew> +		   && !rust_enum_p (type)))
Andrew> +	      && rust_slice_type_p (type)
Andrew> +	      && strcmp (TYPE_NAME (type), "&str") == 0));

I didn't understand the reason for TYPE_CODE_UNION here.

Also, I think an array or slice of 'char' should probably be considered
a string in Rust.  See rust_chartype_p.

thanks,
Tom