Avoid some manual memory management in Python

This changes a few places in the Python code to avoid manual memory
management, in favor of letting std::string do the work.

ChangeLog
2017-08-03  Tom Tromey  <tom@tromey.com>

	* python/python.c (compute_python_string): Return std::string.
	(gdbpy_eval_from_control_command): Update.
	(do_start_initialization): Use std::string.
	* python/py-varobj.c (py_varobj_iter_next): Use string_printf, not
	xstrprintf.
	* python/py-breakpoint.c (local_setattro): Use string_printf, not
	xstrprintf.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2017-08-03  Tom Tromey  <tom@tromey.com>
+
+	* python/python.c (compute_python_string): Return std::string.
+	(gdbpy_eval_from_control_command): Update.
+	(do_start_initialization): Use std::string.
+	* python/py-varobj.c (py_varobj_iter_next): Use string_printf, not
+	xstrprintf.
+	* python/py-breakpoint.c (local_setattro): Use string_printf, not
+	xstrprintf.
+
 2017-08-03  Tom Tromey  <tom@tromey.com>
 
 	* top.h (do_restore_instream_cleanup): Remove.

gdb/python/py-breakpoint.c

@@ -1026,15 +1026,12 @@ local_setattro (PyObject *self, PyObject *name, PyObject *v)
 	extlang = get_breakpoint_cond_ext_lang (obj->bp, EXT_LANG_PYTHON);
       if (extlang != NULL)
 	{
-	  char *error_text;
-
-	  error_text
-	    = xstrprintf (_("Only one stop condition allowed.  There is"
-			    " currently a %s stop condition defined for"
-			    " this breakpoint."),
-			  ext_lang_capitalized_name (extlang));
-	  PyErr_SetString (PyExc_RuntimeError, error_text);
-	  xfree (error_text);
+	  std::string error_text
+	    = string_printf (_("Only one stop condition allowed.  There is"
+			       " currently a %s stop condition defined for"
+			       " this breakpoint."),
+			     ext_lang_capitalized_name (extlang));
+	  PyErr_SetString (PyExc_RuntimeError, error_text.c_str ());
 	  return -1;
 	}
     }

gdb/python/py-varobj.c

@@ -71,7 +71,6 @@ py_varobj_iter_next (struct varobj_iter *self)
       if (PyErr_ExceptionMatches (gdbpy_gdb_memory_error))
 	{
 	  PyObject *type, *value, *trace;
-	  char *name_str;
 
 	  PyErr_Fetch (&type, &value, &trace);
 	  gdb::unique_xmalloc_ptr<char>
@@ -85,10 +84,10 @@ py_varobj_iter_next (struct varobj_iter *self)
 	      return NULL;
 	    }
 
-	  name_str = xstrprintf ("<error at %d>",
-				 self->next_raw_index++);
-	  item.reset (Py_BuildValue ("(ss)", name_str, value_str.get ()));
-	  xfree (name_str);
+	  std::string name_str = string_printf ("<error at %d>",
+						self->next_raw_index++);
+	  item.reset (Py_BuildValue ("(ss)", name_str.c_str (),
+				     value_str.get ()));
 	  if (item == NULL)
 	    {
 	      gdbpy_print_stack ();

gdb/python/python.c

@@ -365,32 +365,19 @@ python_run_simple_file (FILE *file, const char *filename)
 }
 
 /* Given a command_line, return a command string suitable for passing
-   to Python.  Lines in the string are separated by newlines.  The
-   return value is allocated using xmalloc and the caller is
-   responsible for freeing it.  */
+   to Python.  Lines in the string are separated by newlines.  */
 
-static char *
+static std::string
 compute_python_string (struct command_line *l)
 {
   struct command_line *iter;
-  char *script = NULL;
-  int size = 0;
-  int here;
+  std::string script;
 
-  for (iter = l; iter; iter = iter->next)
-    size += strlen (iter->line) + 1;
-
-  script = (char *) xmalloc (size + 1);
-  here = 0;
   for (iter = l; iter; iter = iter->next)
     {
-      int len = strlen (iter->line);
-
-      strcpy (&script[here], iter->line);
-      here += len;
-      script[here++] = '\n';
+      script += iter->line;
+      script += '\n';
     }
-  script[here] = '\0';
   return script;
 }
 
@@ -402,16 +389,14 @@ gdbpy_eval_from_control_command (const struct extension_language_defn *extlang,
 				 struct command_line *cmd)
 {
   int ret;
-  char *script;
 
   if (cmd->body_count != 1)
     error (_("Invalid \"python\" block structure."));
 
   gdbpy_enter enter_py (get_current_arch (), current_language);
 
-  script = compute_python_string (cmd->body_list[0]);
-  ret = PyRun_SimpleString (script);
-  xfree (script);
+  std::string script = compute_python_string (cmd->body_list[0]);
+  ret = PyRun_SimpleString (script.c_str ());
   if (ret)
     error (_("Error while executing Python code."));
 }
@@ -1532,7 +1517,6 @@ do_start_initialization ()
 #ifdef IS_PY3K
   int i;
   size_t progsize, count;
-  char *oldloc;
   wchar_t *progname_copy;
 #endif
 
@@ -1546,25 +1530,22 @@ do_start_initialization ()
   progname = concat (ldirname (python_libdir).c_str (), SLASH_STRING, "bin",
 		     SLASH_STRING, "python", (char *) NULL);
 #ifdef IS_PY3K
-  oldloc = xstrdup (setlocale (LC_ALL, NULL));
+  std::string oldloc = setlocale (LC_ALL, NULL);
   setlocale (LC_ALL, "");
   progsize = strlen (progname);
   progname_copy = (wchar_t *) PyMem_Malloc ((progsize + 1) * sizeof (wchar_t));
   if (!progname_copy)
     {
-      xfree (oldloc);
       fprintf (stderr, "out of memory\n");
       return false;
     }
   count = mbstowcs (progname_copy, progname, progsize + 1);
   if (count == (size_t) -1)
     {
-      xfree (oldloc);
       fprintf (stderr, "Could not convert python path to string\n");
       return false;
     }
-  setlocale (LC_ALL, oldloc);
-  xfree (oldloc);
+  setlocale (LC_ALL, oldloc.c_str ());
 
   /* Note that Py_SetProgramName expects the string it is passed to
      remain alive for the duration of the program's execution, so