'struct expression *' -> gdb::unique_xmalloc_ptr<expression>

This patch makes parse_expression and friends return a unique_ptr
instead of raw pointer [1]:

  typedef gdb::unique_malloc_ptr<expression> expression_up;

and then adjusts the codebase throughout to stop using cleanups to
manage lifetime of expression pointers.

Whenever I found a structure owning an expression pointer, I made it
store a unique_ptr instead of a raw pointer, which then requires using
new/delete of the holding structure, instead of XNEW/xfree.

[1] - I'd like to set the rule that types named with an "_up" suffix
      are unique_ptr typedefs.

Note I used gdb::unique_xmalloc_ptr instead of gdb::unique_ptr, simply
because we still use xmalloc instead of new to allocate expression
objects.  Once that's changed, all we need to do is change the
expression_up typedef and the smart pointer will then call delete
instead of xfree.

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

	* ada-lang.c (ada_read_renaming_var_value): Use expression_up.
	(struct ada_catchpoint_location) <excep_cond_expr>: Now an
	expression_up.
	(ada_catchpoint_location_dtor): Reset excep_cond_expr instead of
	using xfree.
	(create_excep_cond_exprs): Use expression_up and gdb::move.
	(allocate_location_exception): Use new instead of XNEW.
	(should_stop_exception): Likewise.  Adjust to use expression_up.
	(create_ada_exception_catchpoint): Use new instead of XNEW.
	* ax-gdb.c (agent_eval_command_one): Use expression_up instead of
	cleanups.
	(maint_agent_printf_command): Use expression_up.
	* break-catch-sig.c (create_signal_catchpoint): Use new instead of
	XNEW.
	* break-catch-syscall.c (create_syscall_event_catchpoint):
	Likewise.
	* break-catch-throw.c (handle_gnu_v3_exceptions): Use new instead
	of XCNEW.  Use gdb::unique_ptr instead of cleanups.
	* breakpoint.c (set_breakpoint_condition, update_watchpoint)
	(parse_cmd_to_aexpr, watchpoint_check)
	(bpstat_check_breakpoint_conditions, watchpoint_locations_match):
	Adjust to use expression_up.
	(init_bp_location): Adjust.
	(free_bp_location): Use delete instead of xfree.
	(set_raw_breakpoint_without_location, set_raw_breakpoint)
	(add_solib_catchpoint, create_fork_vfork_event_catchpoint)
	(new_single_step_breakpoint, create_breakpoint_sal): Use new
	instead of XNEW.
	(find_condition_and_thread): Adjust to use expression_up.
	(create_breakpoint): Use new instead of XNEW.
	(dtor_watchpoint): Don't xfree expression pointers, they're
	unique_ptr's now.
	(insert_watchpoint, remove_watchpoint): Adjust.
	(watch_command_1): Use expression_up.  Use new instead of XCNEW.
	(catch_exec_command_1): Use new instead of XNEW.
	(bp_location_dtor): Don't xfree expression pointers, they're
	unique_ptr's now.
	(base_breakpoint_allocate_location)
	(strace_marker_create_breakpoints_sal): Use new instead of XNEW.
	(delete_breakpoint): Use delete instead of xfree.
	* breakpoint.h (struct bp_location) <cond>: Now an
	unique_ptr<expression> instead of a raw pointer.
	(struct watchpoint) <exp, cond_exp>: Likewise.
	* cli/cli-script.c (execute_control_command): Use expression_up
	instead of cleanups.
	* dtrace-probe.c (dtrace_process_dof_probe): Use expression_up.
	* eval.c (parse_and_eval_address, parse_and_eval_long)
	(parse_and_eval, parse_to_comma_and_eval, parse_and_eval_type):
	Use expression_up instead of cleanups.
	* expression.h (expression_up): New typedef.
	(parse_expression, parse_expression_with_language, parse_exp_1):
	Change return type to expression_up.
	* mi/mi-main.c (mi_cmd_data_evaluate_expression)
	(print_variable_or_computed): Use expression_up.
	* objc-lang.c (print_object_command): Use expression_up instead of
	cleanups.
	* parse.c (parse_exp_1, parse_exp_in_context)
	(parse_exp_in_context_1, parse_expression)
	(parse_expression_with_language): Return an expression_up instead
	of a raw pointer.
	(parse_expression_for_completion): Use expression_up.
	* printcmd.c (struct display) <exp>: Now an expression_up instead
	of a raw pointer.
	(print_command_1, output_command_const, set_command, x_command):
	Use expression_up instead of cleanups.
	(display_command): Likewise.  Use new instead of XNEW.
	(free_display): Use delete instead of xfree.
	(do_one_display): Adjust to use expression_up.
	* remote.c (remote_download_tracepoint): Likewise.
	* stack.c (return_command): Likewise.
	* tracepoint.c (validate_actionline, encode_actions_1): Use
	expression_up instead of cleanups.
	* typeprint.c (whatis_exp, maintenance_print_type): Likewise.
	* value.c (init_if_undefined_command): Likewise.
	* varobj.c (struct varobj_root) <exp>: Now an expression_up
	instead of a raw pointer.
	(varobj_create): Adjust.
	(varobj_set_value): Use an expression_up instead of cleanups.
	(new_root_variable): Use new instead of XNEW.
	(free_variable): Use delete instead of xfree.
	(value_of_root_1): Use std::swap.

gdb/parse.c

@@ -115,12 +115,12 @@ static void free_funcalls (void *ignore);
 static int prefixify_subexp (struct expression *, struct expression *, int,
 			     int);
 
-static struct expression *parse_exp_in_context (const char **, CORE_ADDR,
-						const struct block *, int, 
-						int, int *);
-static struct expression *parse_exp_in_context_1 (const char **, CORE_ADDR,
-						  const struct block *, int,
-						  int, int *);
+static expression_up parse_exp_in_context (const char **, CORE_ADDR,
+					   const struct block *, int,
+					   int, int *);
+static expression_up parse_exp_in_context_1 (const char **, CORE_ADDR,
+					     const struct block *, int,
+					     int, int *);
 
 void _initialize_parse (void);
 
@@ -1108,14 +1108,14 @@ prefixify_subexp (struct expression *inexpr,
 
    If COMMA is nonzero, stop if a comma is reached.  */
 
-struct expression *
+expression_up
 parse_exp_1 (const char **stringptr, CORE_ADDR pc, const struct block *block,
 	     int comma)
 {
   return parse_exp_in_context (stringptr, pc, block, comma, 0, NULL);
 }
 
-static struct expression *
+static expression_up
 parse_exp_in_context (const char **stringptr, CORE_ADDR pc,
 		      const struct block *block,
 		      int comma, int void_context_p, int *out_subexp)
@@ -1131,7 +1131,7 @@ parse_exp_in_context (const char **stringptr, CORE_ADDR pc,
    left-hand-side of the struct op.  If not doing such completion, it
    is left untouched.  */
 
-static struct expression *
+static expression_up
 parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
 			const struct block *block,
 			int comma, int void_context_p, int *out_subexp)
@@ -1254,18 +1254,16 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
   discard_cleanups (old_chain);
 
   *stringptr = lexptr;
-  return ps.expout;
+  return expression_up (ps.expout);
 }
 
 /* Parse STRING as an expression, and complain if this fails
    to use up all of the contents of STRING.  */
 
-struct expression *
+expression_up
 parse_expression (const char *string)
 {
-  struct expression *exp;
-
-  exp = parse_exp_1 (&string, 0, 0, 0);
+  expression_up exp = parse_exp_1 (&string, 0, 0, 0);
   if (*string)
     error (_("Junk after end of expression."));
   return exp;
@@ -1274,11 +1272,10 @@ parse_expression (const char *string)
 /* Same as parse_expression, but using the given language (LANG)
    to parse the expression.  */
 
-struct expression *
+expression_up
 parse_expression_with_language (const char *string, enum language lang)
 {
   struct cleanup *old_chain = NULL;
-  struct expression *expr;
 
   if (current_language->la_language != lang)
     {
@@ -1286,7 +1283,7 @@ parse_expression_with_language (const char *string, enum language lang)
       set_language (lang);
     }
 
-  expr = parse_expression (string);
+  expression_up expr = parse_expression (string);
 
   if (old_chain != NULL)
     do_cleanups (old_chain);
@@ -1305,14 +1302,14 @@ struct type *
 parse_expression_for_completion (const char *string, char **name,
 				 enum type_code *code)
 {
-  struct expression *exp = NULL;
+  expression_up exp;
   struct value *val;
   int subexp;
 
   TRY
     {
       parse_completion = 1;
-      exp = parse_exp_in_context (&string, 0, 0, 0, 0, &subexp);
+      exp = gdb::move (parse_exp_in_context (&string, 0, 0, 0, 0, &subexp));
     }
   CATCH (except, RETURN_MASK_ERROR)
     {
@@ -1333,24 +1330,17 @@ parse_expression_for_completion (const char *string, char **name,
     }
 
   if (expout_last_struct == -1)
-    {
-      xfree (exp);
-      return NULL;
-    }
+    return NULL;
 
-  *name = extract_field_op (exp, &subexp);
+  *name = extract_field_op (exp.get (), &subexp);
   if (!*name)
-    {
-      xfree (exp);
-      return NULL;
-    }
+    return NULL;
 
   /* This might throw an exception.  If so, we want to let it
      propagate.  */
-  val = evaluate_subexpression_type (exp, subexp);
+  val = evaluate_subexpression_type (exp.get (), subexp);
   /* (*NAME) is a part of the EXP memory block freed below.  */
   *name = xstrdup (*name);
-  xfree (exp);
 
   return value_type (val);
 }