gdb/

* python/py-breakpoint.c (bppy_set_condition): New comment.
	* python/py-cmd.c (cmdpy_function): Call also gdbpy_print_stack for
	failed PyUnicode_Decode.
	(cmdpy_completer): Skip element for failed
	python_string_to_host_string.
	(cmdpy_init): Return -1 on failed python_string_to_host_string.
	* python/py-frame.c (frapy_read_var): Extend the function comment.
	* python/py-function.c (fnpy_init): Return -1 on failed
	python_string_to_host_string.
	* python/py-inferior.c (infpy_read_memory, infpy_write_memory): Extend
	the function comment.
	(infpy_search_memory): Extend the function comment.  Remove the
	PyErr_SetString call on already set error state.
	* python/py-param.c (set_parameter_value): Extend the function
	comment.  Return -1 on failed python_string_to_host_string, twice.
	(set_attr): Extend the function comment.
	(compute_enum_values): Extend the function comment.  New variable
	back_to.  Protect self->enumeration by BACK_TO cleanups.  Return 0 on
	failed python_string_to_host_string.
	(get_doc_string): Call gdbpy_print_stack on failed
	python_string_to_host_string.
	(parmpy_init): Extend the function comment.
	* python/py-prettyprint.c (pretty_print_one_value): Likewise.
	(gdbpy_get_display_hint, print_children): Call gdbpy_print_stack on
	failed python_string_to_host_string.
	* python/py-value.c (valpy_new, valpy_getitem, valpy_call)
	(valpy_binop, valpy_richcompare): Extend the function comment.
	* python/python.c
	(struct python_env) <error_type, error_value, error_traceback>: New
	fields.
	(restore_python_env): Handle PyErr_Occurred.  Call PyErr_Restore.
	(ensure_python_env): Call PyErr_Fetch.
	* varobj.c (update_dynamic_varobj_children): Call gdbpy_print_stack on
	failed convert_value_from_python.
	(value_get_print_value): Call gdbpy_print_stack on failed
	python_string_to_target_python_string.

gdb/testsuite/
	* gdb.python/py-error.exp: New file.
	* gdb.python/py-error.py: New file.

gdb/python/py-inferior.c

@@ -293,7 +293,8 @@ gdbpy_inferiors (PyObject *unused, PyObject *unused2)
 
 /* Implementation of gdb.read_memory (address, length).
    Returns a Python buffer object with LENGTH bytes of the inferior's
-   memory at ADDRESS.  Both arguments are integers.  */
+   memory at ADDRESS.  Both arguments are integers.  Returns NULL on error,
+   with a python exception set.  */
 static PyObject *
 infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
 {
@@ -361,7 +362,8 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
    Writes the contents of BUFFER (a Python object supporting the read
    buffer protocol) at ADDRESS in the inferior's memory.  Write LENGTH
    bytes from BUFFER, or its entire contents if the argument is not
-   provided.  The function returns nothing.  */
+   provided.  The function returns nothing.  Returns NULL on error, with
+   a python exception set.  */
 static PyObject *
 infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
 {
@@ -473,7 +475,8 @@ get_char_buffer (PyObject *self, Py_ssize_t segment, char **ptrptr)
    search from ADDRESS.  PATTERN is the pattern to search for (and
    must be a Python object supporting the buffer protocol).
    Returns a Python Long object holding the address where the pattern
-   was located, or if the pattern was not found, returns None.  */
+   was located, or if the pattern was not found, returns None.  Returns NULL
+   on error, with a python exception set.  */
 static PyObject *
 infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
 {
@@ -511,12 +514,7 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
 	}
     }
   else
-    {
-      PyErr_SetString (PyExc_RuntimeError,
-		       _("Cannot get search address/range from Python."));
-
-      return NULL;
-    }
+    return NULL;
 
   if (!PyObject_CheckReadBuffer (pattern))
     {