gdb: Convert language la_pass_by_reference field to a method

This commit changes the language_data::la_pass_by_reference function
pointer member variable into a member function of language_defn.

The interesting thing in this commit is that I have removed the
default_pass_by_reference function entirely.  This function only ever
returned a language_pass_by_ref_info struct in its default state, so
all uses of this function can be replaced by just default
initialisation of a language_pass_by_ref_info variable.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* ada-lang.c (ada_language_data): Delete la_pass_by_reference
	initializer.
	* c-lang.c (c_language_data): Likewise.
	(cplus_language_data): Likewise.
	(cplus_language::pass_by_reference_info): New method.
	(asm_language_data): Delete la_pass_by_reference initializer.
	(minimal_language_data): Likewise.
	* cp-abi.c (cp_pass_by_reference): Remove use of
	default_pass_by_reference.
	* d-lang.c (d_language_data): Likewise.
	* f-lang.c (f_language_data): Likewise.
	* gnu-v3-abi.c (gnuv3_pass_by_reference): Remove use of
	default_pass_by_reference.
	* go-lang.c (go_language_data): Likewise.
	* language.c (language_pass_by_reference): Update.
	(default_pass_by_reference): Delete.
	(unknown_language_data): Delete la_pass_by_reference
	initializer.
	(auto_language_data): Likewise.
	* language.h (struct language_data): Delete la_pass_by_reference
	field.
	(language_defn::pass_by_reference_info): New member function.
	(default_pass_by_reference): Delete declaration.
	* m2-lang.c (m2_language_data): Delete la_pass_by_reference
	initializer.
	* objc-lang.c (objc_language_data): Likewise.
	* opencl-lang.c (opencl_language_data): Likewise.
	* p-lang.c (pascal_language_data): Likewise.
	* rust-lang.c (rust_language_data): Likewise.

gdb/ChangeLog

@@ -1,3 +1,35 @@
+2020-06-02  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* ada-lang.c (ada_language_data): Delete la_pass_by_reference
+	initializer.
+	* c-lang.c (c_language_data): Likewise.
+	(cplus_language_data): Likewise.
+	(cplus_language::pass_by_reference_info): New method.
+	(asm_language_data): Delete la_pass_by_reference initializer.
+	(minimal_language_data): Likewise.
+	* cp-abi.c (cp_pass_by_reference): Remove use of
+	default_pass_by_reference.
+	* d-lang.c (d_language_data): Likewise.
+	* f-lang.c (f_language_data): Likewise.
+	* gnu-v3-abi.c (gnuv3_pass_by_reference): Remove use of
+	default_pass_by_reference.
+	* go-lang.c (go_language_data): Likewise.
+	* language.c (language_pass_by_reference): Update.
+	(default_pass_by_reference): Delete.
+	(unknown_language_data): Delete la_pass_by_reference
+	initializer.
+	(auto_language_data): Likewise.
+	* language.h (struct language_data): Delete la_pass_by_reference
+	field.
+	(language_defn::pass_by_reference_info): New member function.
+	(default_pass_by_reference): Delete declaration.
+	* m2-lang.c (m2_language_data): Delete la_pass_by_reference
+	initializer.
+	* objc-lang.c (objc_language_data): Likewise.
+	* opencl-lang.c (opencl_language_data): Likewise.
+	* p-lang.c (pascal_language_data): Likewise.
+	* rust-lang.c (rust_language_data): Likewise.
+
 2020-06-02  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* ada-lang.c (ada_read_var_value): Delete function, move

gdb/ada-lang.c

@@ -14066,7 +14066,6 @@ extern const struct language_data ada_language_data =
   ada_get_gdb_completer_word_break_characters,
   ada_collect_symbol_completion_matches,
   ada_language_arch_info,
-  default_pass_by_reference,
   ada_watch_location_expression,
   ada_get_symbol_name_matcher,	/* la_get_symbol_name_matcher */
   ada_iterate_over_symbols,

gdb/c-lang.c

@@ -922,7 +922,6 @@ extern const struct language_data c_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   c_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,
@@ -1081,7 +1080,6 @@ extern const struct language_data cplus_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   cplus_language_arch_info,
-  cp_pass_by_reference,
   c_watch_location_expression,
   cp_get_symbol_name_matcher,
   iterate_over_symbols,
@@ -1101,6 +1099,14 @@ public:
   cplus_language ()
     : language_defn (language_cplus, cplus_language_data)
   { /* Nothing.  */ }
+
+  /* See language.h.  */
+
+  struct language_pass_by_ref_info pass_by_reference_info
+	(struct type *type) const override
+  {
+    return cp_pass_by_reference (type);
+  }
 };
 
 /* The single instance of the C++ language class.  */
@@ -1149,7 +1155,6 @@ extern const struct language_data asm_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   c_language_arch_info,		/* FIXME: la_language_arch_info.  */
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,
@@ -1214,7 +1219,6 @@ extern const struct language_data minimal_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   c_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/cp-abi.c

@@ -226,7 +226,7 @@ struct language_pass_by_ref_info
 cp_pass_by_reference (struct type *type)
 {
   if ((current_cp_abi.pass_by_reference) == NULL)
-    return default_pass_by_reference (type);
+    return {};
   return (*current_cp_abi.pass_by_reference) (type);
 }
 

gdb/d-lang.c

@@ -243,7 +243,6 @@ extern const struct language_data d_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   d_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/f-lang.c

@@ -671,7 +671,6 @@ extern const struct language_data f_language_data =
   f_word_break_characters,
   f_collect_symbol_completion_matches,
   f_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   cp_get_symbol_name_matcher,	/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/gnu-v3-abi.c

@@ -1406,8 +1406,7 @@ gnuv3_pass_by_reference (struct type *type)
   type = check_typedef (type);
 
   /* Start with the default values.  */
-  struct language_pass_by_ref_info info
+  struct language_pass_by_ref_info info;
-    = default_pass_by_reference (type);
 
   bool has_cc_attr = false;
   bool is_pass_by_value = false;

gdb/go-lang.c

@@ -614,7 +614,6 @@ extern const struct language_data go_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   go_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/language.c

@@ -627,17 +627,7 @@ language_class_name_from_physname (const struct language_defn *lang,
 struct language_pass_by_ref_info
 language_pass_by_reference (struct type *type)
 {
-  return current_language->la_pass_by_reference (type);
+  return current_language->pass_by_reference_info (type);
-}
-
-/* Return a default struct that provides pass-by-reference information
-   about the given TYPE.  Languages should update the default values
-   as appropriate.  */
-
-struct language_pass_by_ref_info
-default_pass_by_reference (struct type *type)
-{
-  return {};
 }
 
 /* Return the default string containing the list of characters
@@ -848,7 +838,6 @@ extern const struct language_data unknown_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   unknown_language_arch_info,	/* la_language_arch_info.  */
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,
@@ -911,7 +900,6 @@ extern const struct language_data auto_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   unknown_language_arch_info,	/* la_language_arch_info.  */
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/language.h

@@ -372,11 +372,6 @@ struct language_data
     void (*la_language_arch_info) (struct gdbarch *,
 				   struct language_arch_info *);
 
-    /* Return information about whether TYPE should be passed
-       (and returned) by reference at the language level.  */
-    struct language_pass_by_ref_info (*la_pass_by_reference)
-      (struct type *type);
-
     /* Return an expression that can be used for a location
        watchpoint.  TYPE is a pointer type that points to the memory
        to watch, and ADDR is the address of the watched memory.  */
@@ -497,6 +492,17 @@ struct language_defn : language_data
 					const struct block *var_block,
 					struct frame_info *frame) const;
 
+  /* Return information about whether TYPE should be passed
+     (and returned) by reference at the language level.  The default
+     implementation returns a LANGUAGE_PASS_BY_REF_INFO initialised in its
+     default state.  */
+
+  virtual struct language_pass_by_ref_info pass_by_reference_info
+	(struct type *type) const
+  {
+    return {};
+  }
+
   /* List of all known languages.  */
   static const struct language_defn *languages[nr_languages];
 };
@@ -669,11 +675,6 @@ extern const char *default_word_break_characters (void);
    (and returned) by reference at the language level.  */
 struct language_pass_by_ref_info language_pass_by_reference (struct type *type);
 
-/* Return a default struct that provides pass-by-reference information
-   about the given TYPE.  Languages should update the default values
-   as appropriate.  */
-struct language_pass_by_ref_info default_pass_by_reference (struct type *type);
-
 /* The default implementation of la_print_typedef.  */
 void default_print_typedef (struct type *type, struct symbol *new_symbol,
 			    struct ui_file *stream);

gdb/m2-lang.c

@@ -412,7 +412,6 @@ extern const struct language_data m2_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   m2_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/objc-lang.c

@@ -401,7 +401,6 @@ extern const struct language_data objc_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   c_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/opencl-lang.c

@@ -1078,7 +1078,6 @@ extern const struct language_data opencl_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   opencl_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,

gdb/p-lang.c

@@ -465,7 +465,6 @@ extern const struct language_data pascal_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   pascal_language_arch_info,
-  default_pass_by_reference,
   c_watch_location_expression,
   NULL,				/* la_compare_symbol_for_completion */
   iterate_over_symbols,

gdb/rust-lang.c

@@ -2138,7 +2138,6 @@ extern const struct language_data rust_language_data =
   default_word_break_characters,
   default_collect_symbol_completion_matches,
   rust_language_arch_info,
-  default_pass_by_reference,
   rust_watch_location_expression,
   NULL,				/* la_get_symbol_name_matcher */
   iterate_over_symbols,