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

[Andrew Burgess <andrew.burgess@embecosm.com>]

* Tom Tromey <tom@tromey.com> [2019-04-19 08:45:03 -0600]:

> >>>>> "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.

Do you think that this applied on top of the previous would catch all
of the pointer cases?

I don't think we need to call classify_type as that seems to assume
that by the time it's called we know we have a character type of some
description, so I think calling c_textual_element_type is enough...

Let me know if you think I've missed something,

thanks,
Andrew

---

diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index 4d5284e2e80..aeffefad55e 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -739,6 +739,11 @@ c_is_string_type_p (struct type *type)
       }
     case TYPE_CODE_STRING:
       return true;
+    case TYPE_CODE_PTR:
+      {
+	struct type *element_type = TYPE_TARGET_TYPE (type);
+	return c_textual_element_type (element_type, 0);
+      }
     default:
       break;
     }