gdb: Introduce new language field la_is_string_type_p

This commit is preparation work for the next commit, and by itself
makes no user visible change to GDB.  I've split this work into a
separate commit in order to make code review easier.

This commit adds a new field 'la_is_string_type_p' to the language
struct, this predicate will return true if a type is a string type for
the given language.

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

A default "is this a string" method has also been added that looks for
TYPE_CODE_STRING, this is the fallback I've used for a couple of
languages.

In this commit I add the new field and initialise it for each
language, however at this stage the new field is never used.

gdb/ChangeLog:

	* ada-lang.c (ada_language_defn): Initialise new field.
	* c-lang.c (c_is_string_type_p): New function.
	(c_language_defn): Initialise new field.
	(cplus_language_defn): Initialise new field.
	(asm_language_defn): Initialise new field.
	(minimal_language_defn): Initialise new field.
	* c-lang.h (c_is_string_type_p): Declare new function.
	* d-lang.c (d_language_defn): Initialise new field.
	* f-lang.c (f_is_string_type_p): New function.
	(f_language_defn): Initialise new field.
	* go-lang.c (go_is_string_type_p): New function.
	(go_language_defn): Initialise new field.
	* language.c (default_is_string_type_p): New function.
	(unknown_language_defn): Initialise new field.
	(auto_language_defn): Initialise new field.
	* language.h (struct language_defn) <la_is_string_type_p>: New
	member variable.
	(default_is_string_type_p): Declare new function.
	* m2-lang.c (m2_language_defn): Initialise new field.
	* objc-lang.c (objc_language_defn): Initialise new field.
	* opencl-lang.c (opencl_language_defn): Initialise new field.
	* p-lang.c (pascal_is_string_type_p): New function.
	(pascal_language_defn): Initialise new field.
	* rust-lang.c (rust_is_string_type_p): New function.
	(rust_language_defn): Initialise new field.

1 files changed, 11 insertions, 0 deletions

diff --git a/gdb/p-lang.c b/gdb/p-lang.c
index 0b85f70dfd2..9b9f19b69cf 100644
--- a/gdb/p-lang.c
+++ b/gdb/p-lang.c
@@ -150,6 +150,16 @@ is_pascal_string_type (struct type *type,int *length_pos,
   return 0;
 }
 
+/* This is a wrapper around IS_PASCAL_STRING_TYPE that returns true if TYPE
+   is a string.  */
+
+static bool
+pascal_is_string_type_p (struct type *type)
+{
+  return is_pascal_string_type (type, nullptr, nullptr, nullptr,
+				nullptr, nullptr) > 0;
+}
+
 static void pascal_one_char (int, struct ui_file *, int *);
 
 /* Print the character C on STREAM as part of the contents of a literal
@@ -460,5 +470,6 @@ extern const struct language_defn pascal_language_defn =
   &default_varobj_ops,
   NULL,
   NULL,
+  pascal_is_string_type_p,
   "{...}"			/* la_struct_too_deep_ellipsis */
 };