Use ui_file_as_string throughout more

This replaces most of the remaining ui_file_xstrdup calls with
ui_file_as_string calls.  Whenever a call was replaced, that led to a
cascade of other necessary adjustments throughout, to make the code
use std::string instead of raw pointers.  And then whenever I added a
std::string as member of a struct, I needed to adjust
allocation/destruction of said struct to use new/delete instead of
xmalloc/xfree.

The stopping point was once gdb built again.  These doesn't seem to be
a way to reasonably split this out further.

Maybe-not-obvious changes:

 - demangle_for_lookup returns a cleanup today.  To get rid of that,
   and avoid unnecessary string dupping/copying, this introduces a
   demangle_result_storage type that the caller instantiates and
   passes to demangle_for_lookup.

 - Many methods returned a "char *" to indicate that the caller owns
   the memory and must free it.  Those are switched to return a
   std::string instead.  Methods that return a "view" into some
   internal string return a "const char *" instead.  I.e., we only
   copy/allocate when necessary.

gdb/ChangeLog:
2016-11-08  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_name_for_lookup, type_as_string): Use and return
	std::string.
	(type_as_string_and_cleanup): Delete.
	(ada_lookup_struct_elt_type): Use type_as_string.
	* ada-lang.h (ada_name_for_lookup): Now returns std::string.
	* ada-varobj.c (ada_varobj_scalar_image): Return a std::string.
	(ada_varobj_describe_child): Make 'child_name' and
	'child_path_expr' parameters std::string pointers.
	(ada_varobj_describe_struct_child, ada_varobj_describe_ptr_child):
	Likewise, and use string_printf.
	(ada_varobj_describe_simple_array_child)
	(ada_varobj_describe_child): Likewise.
	(ada_varobj_get_name_of_child, ada_varobj_get_path_expr_of_child)
	(ada_varobj_get_value_image)
	(ada_varobj_get_value_of_array_variable)
	(ada_varobj_get_value_of_variable, ada_name_of_variable)
	(ada_name_of_child, ada_path_expr_of_child)
	(ada_value_of_variable): Now returns std::string.  Use
	string_printf.
	(ada_value_of_child): Adjust.
	* break-catch-throw.c (check_status_exception_catchpoint): Adjust
	to use std::string.
	* breakpoint.c (watch_command_1): Adjust to use std::string.
	* c-lang.c (c_get_string): Adjust to use std::string.
	* c-typeprint.c (print_name_maybe_canonical): Use std::string.
	* c-varobj.c (varobj_is_anonymous_child): Use ==/!= std::string
	operators.
	(c_name_of_variable): Now returns a std::string.
	(c_describe_child): The 'cname' and 'cfull_expression' output
	parameters are now std::string pointers.  Adjust.
	(c_name_of_child, c_path_expr_of_child, c_value_of_variable)
	(cplus_number_of_children): Adjust to use std::string and
	string_printf.
	(cplus_name_of_variable): Now returns a std::string.
	(cplus_describe_child): The 'cname' and 'cfull_expression' output
	parameters are now std::string pointers.  Adjust.
	(cplus_name_of_child, cplus_path_expr_of_child)
	(cplus_value_of_variable): Now returns a std::string.
	* cp-abi.c (cplus_typename_from_type_info): Return std::string.
	* cp-abi.h (cplus_typename_from_type_info): Return std::string.
	(struct cp_abi_ops) <get_typename_from_type_info>: Return
	std::string.
	* cp-support.c (inspect_type): Use std::string.
	(cp_canonicalize_string_full, cp_canonicalize_string_no_typedefs)
	(cp_canonicalize_string): Return std::string and adjust.
	* cp-support.h (cp_canonicalize_string)
	(cp_canonicalize_string_no_typedefs, cp_canonicalize_string_full):
	Return std::string.
	* dbxread.c (read_dbx_symtab): Use std::string.
	* dwarf2read.c (dwarf2_canonicalize_name): Adjust to use std::string.
	* gdbcmd.h (lookup_struct_elt_type): Adjust to use std::string.
	* gnu-v3-abi.c (gnuv3_get_typeid): Use std::string.
	(gnuv3_get_typename_from_type_info): Return a std::string and
	adjust.
	(gnuv3_get_type_from_type_info): Adjust to use std::string.
	* guile/guile.c (gdbscm_execute_gdb_command): Adjust to use
	std::string.
	* infcmd.c (print_return_value_1): Adjust to use std::string.
	* linespec.c (find_linespec_symbols): Adjust to
	demangle_for_lookup API change.  Use std::string.
	* mi/mi-cmd-var.c (print_varobj, mi_cmd_var_set_format)
	(mi_cmd_var_info_type, mi_cmd_var_info_path_expression)
	(mi_cmd_var_info_expression, mi_cmd_var_evaluate_expression)
	(mi_cmd_var_assign, varobj_update_one): Adjust to use std::string.
	* minsyms.c (lookup_minimal_symbol): Use std::string.
	* python/py-varobj.c (py_varobj_iter_next): Use new instead of
	XNEW.  vitem->name is a std::string now, adjust.
	* rust-exp.y (convert_ast_to_type, convert_name): Adjust to use
	std::string.
	* stabsread.c (define_symbol): Adjust to use std::string.
	* symtab.c (demangle_for_lookup): Now returns 'const char *'.  Add
	a demangle_result_storage parameter.  Use it for storage.
	(lookup_symbol_in_language)
	(lookup_symbol_in_objfile_from_linkage_name): Adjust to new
	demangle_for_lookup API.
	* symtab.h (struct demangle_result_storage): New type.
	(demangle_for_lookup): Now returns 'const char *'.  Add a
	demangle_result_storage parameter.
	* typeprint.c (type_to_string): Return std::string and use
	ui_file_as_string.
	* value.h (type_to_string): Change return type to std::string.
	* varobj-iter.h (struct varobj_item) <name>: Now a std::string.
	(varobj_iter_delete): Use delete instead of xfree.
	* varobj.c (create_child): Return std::string instead of char * in
	output parameter.
	(name_of_variable, name_of_child, my_value_of_variable): Return
	std::string instead of char *.
	(varobj_create, varobj_get_handle): Constify 'objname' parameter.
	Adjust to std::string fields.
	(varobj_get_objname): Return a const char * instead of a char *.
	(varobj_get_expression): Return a std::string.
	(varobj_list_children): Adjust to use std::string.
	(varobj_get_type): Return a std::string.
	(varobj_get_path_expr): Return a const char * instead of a char *.
	Adjust to std::string fields.
	(varobj_get_formatted_value, varobj_get_value): Return a
	std::string.
	(varobj_set_value): Change type of 'expression' parameter to
	std::string.  Use std::string.
	(install_new_value): Use std::string.
	(delete_variable_1): Adjust to use std::string.
	(create_child): Change the 'name' parameter to a std::string
	reference.  Swap it into the new item's name.
	(create_child_with_value): Swap item's name into the new child's
	name.  Use string_printf.
	(new_variable): Use new instead of XNEW.
	(free_variable): Don't xfree fields that are now std::string.
	(name_of_variable, name_of_child): Now returns std::string.
	(value_of_root): Adjust to use std::string.
	(my_value_of_variable, varobj_value_get_print_value): Return
	and use std::string.
	(varobj_value_get_print_value): Adjust to use ui_file_as_string
	and std::string.
	* varobj.h (struct varobj) <name, path_expr, obj_name,
	print_value>: Now std::string's.
	<name_of_variable, name_of_child, path_expr_of_child,
	value_of_variable>: Return std::string.
	(varobj_create, varobj_get_handle): Constify 'objname' parameter.
	(varobj_get_objname): Return a const char * instead of a char *.
	(varobj_get_expression, varobj_get_type): Return a std::string.
	(varobj_get_path_expr): Return a const char * instead of a char *.
	(varobj_get_formatted_value, varobj_get_value): Return a
	std::string.
	(varobj_set_value): Constify 'expression' parameter.
	(varobj_value_get_print_value): Return a std::string.

gdb/linespec.c

@@ -3268,26 +3268,27 @@ find_linespec_symbols (struct linespec_state *state,
 		       VEC (symbolp) **symbols,
 		       VEC (bound_minimal_symbol_d) **minsyms)
 {
-  struct cleanup *cleanup;
-  char *canon;
+  demangle_result_storage demangle_storage;
+  std::string ada_lookup_storage;
   const char *lookup_name;
 
-  cleanup = demangle_for_lookup (name, state->language->la_language,
-				 &lookup_name);
   if (state->language->la_language == language_ada)
     {
       /* In Ada, the symbol lookups are performed using the encoded
          name rather than the demangled name.  */
-      lookup_name = ada_name_for_lookup (name);
-      make_cleanup (xfree, (void *) lookup_name);
+      ada_lookup_storage = ada_name_for_lookup (name);
+      lookup_name = ada_lookup_storage.c_str ();
+    }
+  else
+    {
+      lookup_name = demangle_for_lookup (name,
+					 state->language->la_language,
+					 demangle_storage);
     }
 
-  canon = cp_canonicalize_string_no_typedefs (lookup_name);
-  if (canon != NULL)
-    {
-      lookup_name = canon;
-      make_cleanup (xfree, canon);
-    }
+  std::string canon = cp_canonicalize_string_no_typedefs (lookup_name);
+  if (!canon.empty ())
+    lookup_name = canon.c_str ();
 
   /* It's important to not call expand_symtabs_matching unnecessarily
      as it can really slow things down (by unnecessarily expanding
@@ -3307,7 +3308,7 @@ find_linespec_symbols (struct linespec_state *state,
   if (VEC_empty (symbolp, *symbols)
       && VEC_empty (bound_minimal_symbol_d, *minsyms))
     {
-      char *klass, *method;
+      std::string klass, method;
       const char *last, *p, *scope_op;
       VEC (symbolp) *classes;
 
@@ -3327,35 +3328,29 @@ find_linespec_symbols (struct linespec_state *state,
 	 we already attempted to lookup the entire name as a symbol
 	 and failed.  */
       if (last == NULL)
-	{
-	  do_cleanups (cleanup);
-	  return;
-	}
+	return;
 
       /* LOOKUP_NAME points to the class name.
 	 LAST points to the method name.  */
-      klass = XNEWVEC (char, last - lookup_name + 1);
-      make_cleanup (xfree, klass);
-      strncpy (klass, lookup_name, last - lookup_name);
-      klass[last - lookup_name] = '\0';
+      klass = std::string (lookup_name, last - lookup_name);
 
       /* Skip past the scope operator.  */
       last += strlen (scope_op);
-      method = XNEWVEC (char, strlen (last) + 1);
-      make_cleanup (xfree, method);
-      strcpy (method, last);
+      method = last;
 
       /* Find a list of classes named KLASS.  */
-      classes = lookup_prefix_sym (state, file_symtabs, klass);
-      make_cleanup (VEC_cleanup (symbolp), &classes);
+      classes = lookup_prefix_sym (state, file_symtabs, klass.c_str ());
+      struct cleanup *old_chain
+	= make_cleanup (VEC_cleanup (symbolp), &classes);
 
       if (!VEC_empty (symbolp, classes))
 	{
 	  /* Now locate a list of suitable methods named METHOD.  */
 	  TRY
 	    {
-	      find_method (state, file_symtabs, klass, method, classes,
-			   symbols, minsyms);
+	      find_method (state, file_symtabs,
+			   klass.c_str (), method.c_str (),
+			   classes, symbols, minsyms);
 	    }
 
 	  /* If successful, we're done.  If NOT_FOUND_ERROR
@@ -3367,9 +3362,9 @@ find_linespec_symbols (struct linespec_state *state,
 	    }
 	  END_CATCH
 	}
-    }
 
-  do_cleanups (cleanup);
+      do_cleanups (old_chain);
+    }
 }
 
 /* Return all labels named NAME in FUNCTION_SYMBOLS.  Return the