Remove cleanups from Rust parser

This removes the few remaining cleanups in the Rust language code.
The main difficulty here was that the earlier code allocated VEC heads
on an obstack.  The new code instead introduces an object that
allocates and maintains the storage for whatever vectors are needed
during the parse.

Regression tested on the buildbot.

ChangeLog
2017-08-05  Tom Tromey  <tom@tromey.com>

	* rust-exp.y (rust_op_ptr, set_field): Remove typedefs.
	(rust_op_vector, rust_set_vector): New typedefs.
	(current_parser): New global.
	(work_obstack): Change to pointer type.  Update all users.
	(rust_ast, pstate): Remove globals.
	(struct rust_parser): New.
	(%union) <params, field_inits>: Change type.
	(start, tuple_expr, unit_expr, struct_expr_list, literal)
	(field_expr, expr_list, maybe_expr_list, type_list): Update.
	(ast_call_ish, ast_path, ast_function_type, ast_tuple_type)
	(convert_params_to_types, convert_params_to_expression): Change
	type of "params".
	(ast_string): Change type of "fields".
	(rust_parse): Make a rust_parser.  Remove cleanups.
	(rust_lex_tests): Make and install an auto_obstack.

1 files changed, 184 insertions, 162 deletions

diff --git a/gdb/rust-exp.y b/gdb/rust-exp.y
index 3ac78a3..30c0cb4 100644
--- a/gdb/rust-exp.y
+++ b/gdb/rust-exp.y
@@ -42,8 +42,7 @@
 extern initialize_file_ftype _initialize_rust_exp;
 
 struct rust_op;
-typedef const struct rust_op *rust_op_ptr;
-DEF_VEC_P (rust_op_ptr);
+typedef std::vector<const struct rust_op *> rust_op_vector;
 
 /* A typed integer constant.  */
 
@@ -70,10 +69,7 @@ struct set_field
   const struct rust_op *init;
 };
 
-typedef struct set_field set_field;
-
-DEF_VEC_O (set_field);
-
+typedef std::vector<set_field> rust_set_vector;
 
 static int rustyylex (void);
 static void rust_push_back (char c);
@@ -110,12 +106,12 @@ static const struct rust_op *ast_cast (const struct rust_op *expr,
 				       const struct rust_op *type);
 static const struct rust_op *ast_call_ish (enum exp_opcode opcode,
 					   const struct rust_op *expr,
-					   VEC (rust_op_ptr) **params);
+					   rust_op_vector *params);
 static const struct rust_op *ast_path (struct stoken name,
-				       VEC (rust_op_ptr) **params);
+				       rust_op_vector *params);
 static const struct rust_op *ast_string (struct stoken str);
 static const struct rust_op *ast_struct (const struct rust_op *name,
-					 VEC (set_field) **fields);
+					 rust_set_vector *fields);
 static const struct rust_op *ast_range (const struct rust_op *lhs,
 					const struct rust_op *rhs);
 static const struct rust_op *ast_array_type (const struct rust_op *lhs,
@@ -125,13 +121,13 @@ static const struct rust_op *ast_reference_type (const struct rust_op *type);
 static const struct rust_op *ast_pointer_type (const struct rust_op *type,
 					       int is_mut);
 static const struct rust_op *ast_function_type (const struct rust_op *result,
-						VEC (rust_op_ptr) **params);
-static const struct rust_op *ast_tuple_type (VEC (rust_op_ptr) **params);
+						rust_op_vector *params);
+static const struct rust_op *ast_tuple_type (rust_op_vector *params);
 
-/* The state of the parser, used internally when we are parsing the
-   expression.  */
+/* The current rust parser.  */
 
-static struct parser_state *pstate = NULL;
+struct rust_parser;
+static rust_parser *current_parser;
 
 /* A regular expression for matching Rust numbers.  This is split up
    since it is very long and this gives us a way to comment the
@@ -183,13 +179,76 @@ static regex_t number_regex;
 
 static int unit_testing;
 
-/* Obstack for data temporarily allocated during parsing.  */
-
-static auto_obstack work_obstack;
-
-/* Result of parsing.  Points into work_obstack.  */
-
-static const struct rust_op *rust_ast;
+/* Obstack for data temporarily allocated during parsing.  Points to
+   the obstack in the rust_parser, or to a temporary obstack during
+   unit testing.  */
+
+static auto_obstack *work_obstack;
+
+/* An instance of this is created before parsing, and destroyed when
+   parsing is finished.  */
+
+struct rust_parser
+{
+  rust_parser (struct parser_state *state)
+    : rust_ast (nullptr),
+      pstate (state)
+  {
+    gdb_assert (current_parser == nullptr);
+    current_parser = this;
+    work_obstack = &obstack;
+  }
+
+  ~rust_parser ()
+  {
+    /* Clean up the globals we set.  */
+    current_parser = nullptr;
+    work_obstack = nullptr;
+  }
+
+  /* Create a new rust_set_vector.  The storage for the new vector is
+     managed by this class.  */
+  rust_set_vector *new_set_vector ()
+  {
+    rust_set_vector *result = new rust_set_vector;
+    set_vectors.push_back (std::unique_ptr<rust_set_vector> (result));
+    return result;
+  }
+
+  /* Create a new rust_ops_vector.  The storage for the new vector is
+     managed by this class.  */
+  rust_op_vector *new_op_vector ()
+  {
+    rust_op_vector *result = new rust_op_vector;
+    op_vectors.push_back (std::unique_ptr<rust_op_vector> (result));
+    return result;
+  }
+
+  /* Return the parser's language.  */
+  const struct language_defn *language () const
+  {
+    return parse_language (pstate);
+  }
+
+  /* Return the parser's gdbarch.  */
+  struct gdbarch *arch () const
+  {
+    return parse_gdbarch (pstate);
+  }
+
+  /* A pointer to this is installed globally.  */
+  auto_obstack obstack;
+
+  /* Result of parsing.  Points into obstack.  */
+  const struct rust_op *rust_ast;
+
+  /* This keeps track of the various vectors we allocate.  */
+  std::vector<std::unique_ptr<rust_set_vector>> set_vectors;
+  std::vector<std::unique_ptr<rust_op_vector>> op_vectors;
+
+  /* The parser state gdb gave us.  */
+  struct parser_state *pstate;
+};
 
 %}
 
@@ -209,10 +268,10 @@ static const struct rust_op *rust_ast;
 
   /* A list of expressions; for example, the arguments to a function
      call.  */
-  VEC (rust_op_ptr) **params;
+  rust_op_vector *params;
 
   /* A list of field initializers.  */
-  VEC (set_field) **field_inits;
+  rust_set_vector *field_inits;
 
   /* A single field initializer.  */
   struct set_field one_field_init;
@@ -354,8 +413,8 @@ start:
 		{
 		  /* If we are completing and see a valid parse,
 		     rust_ast will already have been set.  */
-		  if (rust_ast == NULL)
-		    rust_ast = $1;
+		  if (current_parser->rust_ast == NULL)
+		    current_parser->rust_ast = $1;
 		}
 ;
 
@@ -381,7 +440,7 @@ expr:
 tuple_expr:
 	'(' expr ',' maybe_expr_list ')'
 		{
-		  VEC_safe_insert (rust_op_ptr, *$4, 0, $2);
+		  $4->push_back ($2);
 		  error (_("Tuple expressions not supported yet"));
 		}
 ;
@@ -392,8 +451,8 @@ unit_expr:
 		  struct typed_val_int val;
 
 		  val.type
-		    = language_lookup_primitive_type (parse_language (pstate),
-						      parse_gdbarch (pstate),
+		    = language_lookup_primitive_type (current_parser->language (),
+						      current_parser->arch (),
 						      "()");
 		  val.val = 0;
 		  $$ = ast_literal (val);
@@ -432,18 +491,12 @@ struct_expr_tail:
 struct_expr_list:
 	/* %empty */
 		{
-		  VEC (set_field) **result
-		    = OBSTACK_ZALLOC (&work_obstack, VEC (set_field) *);
-		  $$ = result;
+		  $$ = current_parser->new_set_vector ();
 		}
 |	struct_expr_tail
 		{
-		  VEC (set_field) **result
-		    = OBSTACK_ZALLOC (&work_obstack, VEC (set_field) *);
-
-		  make_cleanup (VEC_cleanup (set_field), result);
-		  VEC_safe_push (set_field, *result, &$1);
-
+		  rust_set_vector *result = current_parser->new_set_vector ();
+		  result->push_back ($1);
 		  $$ = result;
 		}
 |	IDENT ':' expr ',' struct_expr_list
@@ -452,7 +505,7 @@ struct_expr_list:
 
 		  sf.name = $1;
 		  sf.init = $3;
-		  VEC_safe_push (set_field, *$5, &sf);
+		  $5->push_back (sf);
 		  $$ = $5;
 		}
 ;
@@ -489,19 +542,17 @@ literal:
 |	STRING
 		{
 		  const struct rust_op *str = ast_string ($1);
-		  VEC (set_field) **fields;
 		  struct set_field field;
 		  struct typed_val_int val;
 		  struct stoken token;
 
-		  fields = OBSTACK_ZALLOC (&work_obstack, VEC (set_field) *);
-		  make_cleanup (VEC_cleanup (set_field), fields);
+		  rust_set_vector *fields = current_parser->new_set_vector ();
 
 		  /* Wrap the raw string in the &str struct.  */
 		  field.name.ptr = "data_ptr";
 		  field.name.length = strlen (field.name.ptr);
 		  field.init = ast_unary (UNOP_ADDR, ast_string ($1));
-		  VEC_safe_push (set_field, *fields, &field);
+		  fields->push_back (field);
 
 		  val.type = rust_type ("usize");
 		  val.val = $1.length;
@@ -509,7 +560,7 @@ literal:
 		  field.name.ptr = "length";
 		  field.name.length = strlen (field.name.ptr);
 		  field.init = ast_literal (val);
-		  VEC_safe_push (set_field, *fields, &field);
+		  fields->push_back (field);
 
 		  token.ptr = "&str";
 		  token.length = strlen (token.ptr);
@@ -521,8 +572,8 @@ literal:
 		{
 		  struct typed_val_int val;
 
-		  val.type = language_bool_type (parse_language (pstate),
-						 parse_gdbarch (pstate));
+		  val.type = language_bool_type (current_parser->language (),
+						 current_parser->arch ());
 		  val.val = 1;
 		  $$ = ast_literal (val);
 		}
@@ -530,8 +581,8 @@ literal:
 		{
 		  struct typed_val_int val;
 
-		  val.type = language_bool_type (parse_language (pstate),
-						 parse_gdbarch (pstate));
+		  val.type = language_bool_type (current_parser->language (),
+						 current_parser->arch ());
 		  val.val = 0;
 		  $$ = ast_literal (val);
 		}
@@ -543,7 +594,7 @@ field_expr:
 |	expr '.' COMPLETE
 		{
 		  $$ = ast_structop ($1, $3.ptr, 1);
-		  rust_ast = $$;
+		  current_parser->rust_ast = $$;
 		}
 |	expr '.' DECIMAL_INTEGER
 		{ $$ = ast_structop_anonymous ($1, $3); }
@@ -672,13 +723,12 @@ paren_expr:
 expr_list:
 	expr
 		{
-		  $$ = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
-		  make_cleanup (VEC_cleanup (rust_op_ptr), $$);
-		  VEC_safe_push (rust_op_ptr, *$$, $1);
+		  $$ = current_parser->new_op_vector ();
+		  $$->push_back ($1);
 		}
 |	expr_list ',' expr
 		{
-		  VEC_safe_push (rust_op_ptr, *$1, $3);
+		  $1->push_back ($3);
 		  $$ = $1;
 		}
 ;
@@ -687,8 +737,7 @@ maybe_expr_list:
 	/* %empty */
 		{
 		  /* The result can't be NULL.  */
-		  $$ = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
-		  make_cleanup (VEC_cleanup (rust_op_ptr), $$);
+		  $$ = current_parser->new_op_vector ();
 		}
 |	expr_list
 		{ $$ = $1; }
@@ -835,16 +884,13 @@ maybe_type_list:
 type_list:
 	type
 		{
-		  VEC (rust_op_ptr) **result
-		    = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
-
-		  make_cleanup (VEC_cleanup (rust_op_ptr), result);
-		  VEC_safe_push (rust_op_ptr, *result, $1);
+		  rust_op_vector *result = current_parser->new_op_vector ();
+		  result->push_back ($1);
 		  $$ = result;
 		}
 |	type_list ',' type
 		{
-		  VEC_safe_push (rust_op_ptr, *$1, $3);
+		  $1->push_back ($3);
 		  $$ = $1;
 		}
 ;
@@ -911,7 +957,7 @@ static const struct token_info operator_tokens[] =
 static const char *
 rust_copy_name (const char *name, int len)
 {
-  return (const char *) obstack_copy0 (&work_obstack, name, len);
+  return (const char *) obstack_copy0 (work_obstack, name, len);
 }
 
 /* Helper function to make an stoken from a C string.  */
@@ -932,7 +978,7 @@ make_stoken (const char *p)
 static struct stoken
 rust_concat3 (const char *s1, const char *s2, const char *s3)
 {
-  return make_stoken (obconcat (&work_obstack, s1, s2, s3, (char *) NULL));
+  return make_stoken (obconcat (work_obstack, s1, s2, s3, (char *) NULL));
 }
 
 /* Return an AST node referring to NAME, but relative to the crate's
@@ -948,7 +994,7 @@ crate_name (const struct rust_op *name)
 
   if (crate.empty ())
     error (_("Could not find crate for current location"));
-  result = make_stoken (obconcat (&work_obstack, "::", crate.c_str (), "::",
+  result = make_stoken (obconcat (work_obstack, "::", crate.c_str (), "::",
 				  name->left.sval.ptr, (char *) NULL));
 
   return ast_path (result, name->right.params);
@@ -996,12 +1042,12 @@ super_name (const struct rust_op *ident, unsigned int n_supers)
   else
     offset = strlen (scope);
 
-  obstack_grow (&work_obstack, "::", 2);
-  obstack_grow (&work_obstack, scope, offset);
-  obstack_grow (&work_obstack, "::", 2);
-  obstack_grow0 (&work_obstack, ident->left.sval.ptr, ident->left.sval.length);
+  obstack_grow (work_obstack, "::", 2);
+  obstack_grow (work_obstack, scope, offset);
+  obstack_grow (work_obstack, "::", 2);
+  obstack_grow0 (work_obstack, ident->left.sval.ptr, ident->left.sval.length);
 
-  return ast_path (make_stoken ((const char *) obstack_finish (&work_obstack)),
+  return ast_path (make_stoken ((const char *) obstack_finish (work_obstack)),
 		   ident->right.params);
 }
 
@@ -1029,8 +1075,8 @@ rust_type (const char *name)
   if (unit_testing)
     return NULL;
 
-  type = language_lookup_primitive_type (parse_language (pstate),
-					 parse_gdbarch (pstate),
+  type = language_lookup_primitive_type (current_parser->language (),
+					 current_parser->arch (),
 					 name);
   if (type == NULL)
     error (_("Could not find Rust type %s"), name);
@@ -1243,7 +1289,7 @@ lex_string (void)
 	  value = lexptr[0] & 0xff;
 	  if (is_byte && value > 127)
 	    error (_("Non-ASCII value in raw byte string"));
-	  obstack_1grow (&work_obstack, value);
+	  obstack_1grow (work_obstack, value);
 
 	  ++lexptr;
 	}
@@ -1258,11 +1304,11 @@ lex_string (void)
 	  value = lex_escape (is_byte);
 
 	  if (is_byte)
-	    obstack_1grow (&work_obstack, value);
+	    obstack_1grow (work_obstack, value);
 	  else
 	    convert_between_encodings ("UTF-32", "UTF-8", (gdb_byte *) &value,
 				       sizeof (value), sizeof (value),
-				       &work_obstack, translit_none);
+				       work_obstack, translit_none);
 	}
       else if (lexptr[0] == '\0')
 	error (_("Unexpected EOF in string"));
@@ -1271,13 +1317,13 @@ lex_string (void)
 	  value = lexptr[0] & 0xff;
 	  if (is_byte && value > 127)
 	    error (_("Non-ASCII value in byte string"));
-	  obstack_1grow (&work_obstack, value);
+	  obstack_1grow (work_obstack, value);
 	  ++lexptr;
 	}
     }
 
-  rustyylval.sval.length = obstack_object_size (&work_obstack);
-  rustyylval.sval.ptr = (const char *) obstack_finish (&work_obstack);
+  rustyylval.sval.length = obstack_object_size (work_obstack);
+  rustyylval.sval.ptr = (const char *) obstack_finish (work_obstack);
   return is_byte ? BYTESTRING : STRING;
 }
 
@@ -1627,7 +1673,7 @@ static const struct rust_op *
 ast_operation (enum exp_opcode opcode, const struct rust_op *left,
 		const struct rust_op *right)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = opcode;
   result->left.op = left;
@@ -1642,7 +1688,7 @@ static const struct rust_op *
 ast_compound_assignment (enum exp_opcode opcode, const struct rust_op *left,
 			  const struct rust_op *right)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = opcode;
   result->compound_assignment = 1;
@@ -1657,7 +1703,7 @@ ast_compound_assignment (enum exp_opcode opcode, const struct rust_op *left,
 static const struct rust_op *
 ast_literal (struct typed_val_int val)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_LONG;
   result->left.typed_val_int = val;
@@ -1670,7 +1716,7 @@ ast_literal (struct typed_val_int val)
 static const struct rust_op *
 ast_dliteral (struct typed_val_float val)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_DOUBLE;
   result->left.typed_val_float = val;
@@ -1691,7 +1737,7 @@ ast_unary (enum exp_opcode opcode, const struct rust_op *expr)
 static const struct rust_op *
 ast_cast (const struct rust_op *expr, const struct rust_op *type)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = UNOP_CAST;
   result->left.op = expr;
@@ -1706,9 +1752,9 @@ ast_cast (const struct rust_op *expr, const struct rust_op *type)
 
 static const struct rust_op *
 ast_call_ish (enum exp_opcode opcode, const struct rust_op *expr,
-	       VEC (rust_op_ptr) **params)
+	      rust_op_vector *params)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = opcode;
   result->left.op = expr;
@@ -1720,9 +1766,9 @@ ast_call_ish (enum exp_opcode opcode, const struct rust_op *expr,
 /* Make a structure creation operation.  */
 
 static const struct rust_op *
-ast_struct (const struct rust_op *name, VEC (set_field) **fields)
+ast_struct (const struct rust_op *name, rust_set_vector *fields)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_AGGREGATE;
   result->left.op = name;
@@ -1734,9 +1780,9 @@ ast_struct (const struct rust_op *name, VEC (set_field) **fields)
 /* Make an identifier path.  */
 
 static const struct rust_op *
-ast_path (struct stoken path, VEC (rust_op_ptr) **params)
+ast_path (struct stoken path, rust_op_vector *params)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_VAR_VALUE;
   result->left.sval = path;
@@ -1750,7 +1796,7 @@ ast_path (struct stoken path, VEC (rust_op_ptr) **params)
 static const struct rust_op *
 ast_string (struct stoken str)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_STRING;
   result->left.sval = str;
@@ -1763,7 +1809,7 @@ ast_string (struct stoken str)
 static const struct rust_op *
 ast_structop (const struct rust_op *left, const char *name, int completing)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = STRUCTOP_STRUCT;
   result->completing = completing;
@@ -1779,7 +1825,7 @@ static const struct rust_op *
 ast_structop_anonymous (const struct rust_op *left,
 			 struct typed_val_int number)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = STRUCTOP_ANONYMOUS;
   result->left.op = left;
@@ -1793,7 +1839,7 @@ ast_structop_anonymous (const struct rust_op *left,
 static const struct rust_op *
 ast_range (const struct rust_op *lhs, const struct rust_op *rhs)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_RANGE;
   result->left.op = lhs;
@@ -1807,7 +1853,7 @@ ast_range (const struct rust_op *lhs, const struct rust_op *rhs)
 static struct rust_op *
 ast_basic_type (enum type_code typecode)
 {
-  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+  struct rust_op *result = OBSTACK_ZALLOC (work_obstack, struct rust_op);
 
   result->opcode = OP_TYPE;
   result->typecode = typecode;
@@ -1864,7 +1910,7 @@ ast_pointer_type (const struct rust_op *type, int is_mut)
 /* Create an AST node describing a function type.  */
 
 static const struct rust_op *
-ast_function_type (const struct rust_op *rtype, VEC (rust_op_ptr) **params)
+ast_function_type (const struct rust_op *rtype, rust_op_vector *params)
 {
   struct rust_op *result = ast_basic_type (TYPE_CODE_FUNC);
 
@@ -1876,7 +1922,7 @@ ast_function_type (const struct rust_op *rtype, VEC (rust_op_ptr) **params)
 /* Create an AST node describing a tuple type.  */
 
 static const struct rust_op *
-ast_tuple_type (VEC (rust_op_ptr) **params)
+ast_tuple_type (rust_op_vector *params)
 {
   struct rust_op *result = ast_basic_type (TYPE_CODE_STRUCT);
 
@@ -1933,14 +1979,14 @@ rust_lookup_type (const char *name, const struct block *block)
       return SYMBOL_TYPE (result.symbol);
     }
 
-  type = lookup_typename (parse_language (pstate), parse_gdbarch (pstate),
+  type = lookup_typename (current_parser->language (), current_parser->arch (),
 			  name, NULL, 1);
   if (type != NULL)
     return type;
 
   /* Last chance, try a built-in type.  */
-  return language_lookup_primitive_type (parse_language (pstate),
-					 parse_gdbarch (pstate),
+  return language_lookup_primitive_type (current_parser->language (),
+					 current_parser->arch (),
 					 name);
 }
 
@@ -1953,13 +1999,11 @@ static const char *convert_name (struct parser_state *state,
    types.  */
 
 static std::vector<struct type *>
-convert_params_to_types (struct parser_state *state, VEC (rust_op_ptr) *params)
+convert_params_to_types (struct parser_state *state, rust_op_vector *params)
 {
-  int i;
-  const struct rust_op *op;
   std::vector<struct type *> result;
 
-  for (i = 0; VEC_iterate (rust_op_ptr, params, i, op); ++i)
+  for (const rust_op *op : *params)
     result.push_back (convert_ast_to_type (state, op));
 
   return result;
@@ -2014,7 +2058,7 @@ convert_ast_to_type (struct parser_state *state,
     case TYPE_CODE_FUNC:
       {
 	std::vector<struct type *> args
-	  (convert_params_to_types (state, *operation->right.params));
+	  (convert_params_to_types (state, operation->right.params));
 	struct type **argtypes = NULL;
 
 	type = convert_ast_to_type (state, operation->left.op);
@@ -2031,23 +2075,23 @@ convert_ast_to_type (struct parser_state *state,
     case TYPE_CODE_STRUCT:
       {
 	std::vector<struct type *> args
-	  (convert_params_to_types (state, *operation->left.params));
+	  (convert_params_to_types (state, operation->left.params));
 	int i;
 	struct type *type;
 	const char *name;
 
-	obstack_1grow (&work_obstack, '(');
+	obstack_1grow (work_obstack, '(');
 	for (i = 0; i < args.size (); ++i)
 	  {
 	    std::string type_name = type_to_string (args[i]);
 
 	    if (i > 0)
-	      obstack_1grow (&work_obstack, ',');
-	    obstack_grow_str (&work_obstack, type_name.c_str ());
+	      obstack_1grow (work_obstack, ',');
+	    obstack_grow_str (work_obstack, type_name.c_str ());
 	  }
 
-	obstack_grow_str0 (&work_obstack, ")");
-	name = (const char *) obstack_finish (&work_obstack);
+	obstack_grow_str0 (work_obstack, ")");
+	name = (const char *) obstack_finish (work_obstack);
 
 	/* We don't allow creating new tuple types (yet), but we do
 	   allow looking up existing tuple types.  */
@@ -2080,22 +2124,22 @@ convert_name (struct parser_state *state, const struct rust_op *operation)
     return operation->left.sval.ptr;
 
   std::vector<struct type *> types
-    (convert_params_to_types (state, *operation->right.params));
+    (convert_params_to_types (state, operation->right.params));
 
-  obstack_grow_str (&work_obstack, operation->left.sval.ptr);
-  obstack_1grow (&work_obstack, '<');
+  obstack_grow_str (work_obstack, operation->left.sval.ptr);
+  obstack_1grow (work_obstack, '<');
   for (i = 0; i < types.size (); ++i)
     {
       std::string type_name = type_to_string (types[i]);
 
       if (i > 0)
-	obstack_1grow (&work_obstack, ',');
+	obstack_1grow (work_obstack, ',');
 
-      obstack_grow_str (&work_obstack, type_name.c_str ());
+      obstack_grow_str (work_obstack, type_name.c_str ());
     }
-  obstack_grow_str0 (&work_obstack, ">");
+  obstack_grow_str0 (work_obstack, ">");
 
-  return (const char *) obstack_finish (&work_obstack);
+  return (const char *) obstack_finish (work_obstack);
 }
 
 static void convert_ast_to_expression (struct parser_state *state,
@@ -2108,13 +2152,10 @@ static void convert_ast_to_expression (struct parser_state *state,
 
 static void
 convert_params_to_expression (struct parser_state *state,
-			      VEC (rust_op_ptr) *params,
+			      rust_op_vector *params,
 			      const struct rust_op *top)
 {
-  int i;
-  rust_op_ptr elem;
-
-  for (i = 0; VEC_iterate (rust_op_ptr, params, i, elem); ++i)
+  for (const rust_op *elem : *params)
     convert_ast_to_expression (state, elem, top);
 }
 
@@ -2259,18 +2300,14 @@ convert_ast_to_expression (struct parser_state *state,
 	      {
 		/* This is actually a tuple struct expression, not a
 		   call expression.  */
-		rust_op_ptr elem;
-		int i;
-		VEC (rust_op_ptr) *params = *operation->right.params;
+		rust_op_vector *params = operation->right.params;
 
 		if (TYPE_CODE (type) != TYPE_CODE_NAMESPACE)
 		  {
 		    if (!rust_tuple_struct_type_p (type))
 		      error (_("Type %s is not a tuple struct"), varname);
 
-		    for (i = 0;
-			 VEC_iterate (rust_op_ptr, params, i, elem);
-			 ++i)
+		    for (int i = 0; i < params->size (); ++i)
 		      {
 			char *cell = get_print_cell ();
 
@@ -2279,35 +2316,31 @@ convert_ast_to_expression (struct parser_state *state,
 			write_exp_string (state, make_stoken (cell));
 			write_exp_elt_opcode (state, OP_NAME);
 
-			convert_ast_to_expression (state, elem, top);
+			convert_ast_to_expression (state, (*params)[i], top);
 		      }
 
 		    write_exp_elt_opcode (state, OP_AGGREGATE);
 		    write_exp_elt_type (state, type);
-		    write_exp_elt_longcst (state,
-					   2 * VEC_length (rust_op_ptr,
-							   params));
+		    write_exp_elt_longcst (state, 2 * params->size ());
 		    write_exp_elt_opcode (state, OP_AGGREGATE);
 		    break;
 		  }
 	      }
 	  }
 	convert_ast_to_expression (state, operation->left.op, top);
-	convert_params_to_expression (state, *operation->right.params, top);
+	convert_params_to_expression (state, operation->right.params, top);
 	write_exp_elt_opcode (state, OP_FUNCALL);
-	write_exp_elt_longcst (state, VEC_length (rust_op_ptr,
-						  *operation->right.params));
+	write_exp_elt_longcst (state, operation->right.params->size ());
 	write_exp_elt_longcst (state, OP_FUNCALL);
       }
       break;
 
     case OP_ARRAY:
       gdb_assert (operation->left.op == NULL);
-      convert_params_to_expression (state, *operation->right.params, top);
+      convert_params_to_expression (state, operation->right.params, top);
       write_exp_elt_opcode (state, OP_ARRAY);
       write_exp_elt_longcst (state, 0);
-      write_exp_elt_longcst (state, VEC_length (rust_op_ptr,
-						*operation->right.params) - 1);
+      write_exp_elt_longcst (state, operation->right.params->size () - 1);
       write_exp_elt_longcst (state, OP_ARRAY);
       break;
 
@@ -2374,26 +2407,25 @@ convert_ast_to_expression (struct parser_state *state,
       {
 	int i;
 	int length;
-	struct set_field *init;
-	VEC (set_field) *fields = *operation->right.field_inits;
+	rust_set_vector *fields = operation->right.field_inits;
 	struct type *type;
 	const char *name;
 
 	length = 0;
-	for (i = 0; VEC_iterate (set_field, fields, i, init); ++i)
+	for (const set_field &init : *fields)
 	  {
-	    if (init->name.ptr != NULL)
+	    if (init.name.ptr != NULL)
 	      {
 		write_exp_elt_opcode (state, OP_NAME);
-		write_exp_string (state, init->name);
+		write_exp_string (state, init.name);
 		write_exp_elt_opcode (state, OP_NAME);
 		++length;
 	      }
 
-	    convert_ast_to_expression (state, init->init, top);
+	    convert_ast_to_expression (state, init.init, top);
 	    ++length;
 
-	    if (init->name.ptr == NULL)
+	    if (init.name.ptr == NULL)
 	      {
 		/* This is handled differently from Ada in our
 		   evaluator.  */
@@ -2466,28 +2498,15 @@ rust_parse (struct parser_state *state)
 {
   int result;
 
-  work_obstack.clear ();
-
-  rust_ast = NULL;
-
-  pstate = state;
-
-  /* Note that parsing (within rustyyparse) freely installs cleanups
-     assuming they're run here (below).  */
-  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+  /* This sets various globals and also clears them on
+     destruction.  */
+  rust_parser parser (state);
 
   result = rustyyparse ();
 
-  if (!result || (parse_completion && rust_ast != NULL))
-    {
-      const struct rust_op *ast = rust_ast;
+  if (!result || (parse_completion && parser.rust_ast != NULL))
+    convert_ast_to_expression (state, parser.rust_ast, parser.rust_ast);
 
-      rust_ast = NULL;
-      gdb_assert (ast != NULL);
-      convert_ast_to_expression (state, ast, ast);
-    }
-
-  do_cleanups (cleanup);
   return result;
 }
 
@@ -2654,7 +2673,10 @@ rust_lex_tests (void)
 {
   int i;
 
-  work_obstack.clear ();
+  auto_obstack test_obstack;
+  scoped_restore obstack_holder = make_scoped_restore (&work_obstack,
+						       &test_obstack);
+
   unit_testing = 1;
 
   rust_lex_test_one ("", 0);