Use unique_xmalloc_ptr in Python code

This changes some utility functions in the Python code to return
unique_xmalloc_ptr, and then fixes up the callers.

I chose unique_xmalloc_ptr rather than std::string because at a few
call points the xmalloc'd string is released and ownership transferred
elsewhere.

This patch found a few existing memory leaks.  For example,
py-unwind.c called gdbpy_obj_to_string but never freed the result.

Built and regression tested on the buildbot.

2016-11-09  Tom Tromey  <tom@tromey.com>

	* varobj.h (varobj_get_display_hint): Change return type.
	* varobj.c (varobj_get_display_hint): Return unique_xmalloc_ptr.
	(varobj_value_get_print_value): Update.
	* python/python.c (gdbpy_before_prompt_hook, gdbpy_print_stack)
	(gdbpy_apply_type_printers): Update.
	* python/python-internal.h (unicode_to_target_string)
	(python_string_to_target_string, python_string_to_host_string)
	(gdbpy_obj_to_string, gdbpy_exception_to_string)
	(gdbpy_get_display_hint): Change return types.
	* python/py-varobj.c (py_varobj_iter_next): Update.
	* python/py-value.c (valpy_getitem, convert_value_from_python):
	Update.
	* python/py-utils.c (unicode_to_encoded_string)
	(unicode_to_target_string, python_string_to_target_string)
	(python_string_to_host_string, gdbpy_obj_to_string)
	(gdbpy_exception_to_string): Return unique_xmalloc_ptr.
	* python/py-unwind.c (pyuw_parse_register_id): Update.
	* python/py-type.c (typy_getitem): Update.
	* python/py-prettyprint.c (gdbpy_get_display_hint)
	(print_stack_unless_memory_error, print_children)
	(gdbpy_apply_val_pretty_printer): Update.
	* python/py-param.c (set_parameter_value): Update.
	(get_doc_string, call_doc_function): Return unique_xmalloc_ptr.
	(get_set_value, get_show_value, compute_enum_values, parmpy_init):
	Update.
	* python/py-infthread.c (thpy_set_name): Update.
	* python/py-function.c (fnpy_call, fnpy_init): Update.
	* python/py-framefilter.c (extract_sym): Change "name" to
	unique_xmalloc_ptr.
	(enumerate_args, enumerate_locals): Update.
	(py_print_frame): Use unique_xmalloc_ptr.
	* python/py-frame.c (frapy_read_var): Update.  Remove cleanup.
	* python/py-cmd.c (cmdpy_function, cmdpy_completer, cmdpy_init):
	Update.
	* python/py-breakpoint.c (bppy_set_condition): Use
	unique_xmalloc_ptr.
	(bppy_init): Likewise.  Remove cleanup.
	(local_setattro): Update.
	* mi/mi-cmd-var.c (print_varobj, mi_cmd_var_list_children)
	(varobj_update_one): Update.

1 files changed, 7 insertions, 18 deletions

diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
index 147e026..4131f99 100644
--- a/gdb/mi/mi-cmd-var.c
+++ b/gdb/mi/mi-cmd-var.c
@@ -50,7 +50,6 @@ print_varobj (struct varobj *var, enum print_values print_values,
 {
   struct ui_out *uiout = current_uiout;
   int thread_id;
-  char *display_hint;
 
   ui_out_field_string (uiout, "name", varobj_get_objname (var));
   if (print_expression)
@@ -79,12 +78,9 @@ print_varobj (struct varobj *var, enum print_values print_values,
   if (varobj_get_frozen (var))
     ui_out_field_int (uiout, "frozen", 1);
 
-  display_hint = varobj_get_display_hint (var);
+  gdb::unique_xmalloc_ptr<char> display_hint = varobj_get_display_hint (var);
   if (display_hint)
-    {
-      ui_out_field_string (uiout, "displayhint", display_hint);
-      xfree (display_hint);
-    }
+    ui_out_field_string (uiout, "displayhint", display_hint.get ());
 
   if (varobj_is_dynamic_p (var))
     ui_out_field_int (uiout, "dynamic", 1);
@@ -378,7 +374,6 @@ mi_cmd_var_list_children (char *command, char **argv, int argc)
   enum print_values print_values;
   int ix;
   int from, to;
-  char *display_hint;
 
   if (argc < 1 || argc > 4)
     error (_("-var-list-children: Usage: "
@@ -408,12 +403,9 @@ mi_cmd_var_list_children (char *command, char **argv, int argc)
   else
     print_values = PRINT_NO_VALUES;
 
-  display_hint = varobj_get_display_hint (var);
+  gdb::unique_xmalloc_ptr<char> display_hint = varobj_get_display_hint (var);
   if (display_hint)
-    {
-      ui_out_field_string (uiout, "displayhint", display_hint);
-      xfree (display_hint);
-    }
+    ui_out_field_string (uiout, "displayhint", display_hint.get ());
 
   if (from < to)
     {
@@ -721,7 +713,6 @@ varobj_update_one (struct varobj *var, enum print_values print_values,
   
   for (i = 0; VEC_iterate (varobj_update_result, changes, i, r); ++i)
     {
-      char *display_hint;
       int from, to;
       struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
 
@@ -767,12 +758,10 @@ varobj_update_one (struct varobj *var, enum print_values print_values,
 	ui_out_field_int (uiout, "new_num_children", 
 			  varobj_get_num_children (r->varobj));
 
-      display_hint = varobj_get_display_hint (r->varobj);
+      gdb::unique_xmalloc_ptr<char> display_hint
+	= varobj_get_display_hint (r->varobj);
       if (display_hint)
-	{
-	  ui_out_field_string (uiout, "displayhint", display_hint);
-	  xfree (display_hint);
-	}
+	ui_out_field_string (uiout, "displayhint", display_hint.get ());
 
       if (varobj_is_dynamic_p (r->varobj))
 	ui_out_field_int (uiout, "dynamic", 1);