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Fix Python completion when using the "complete" command

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This patch is related to PR python/16699, and is an improvement over the
patch posted here:

  <https://sourceware.org/ml/gdb-patches/2014-03/msg00301.html>

Keith noticed that, when using the "complete" command on GDB to complete
a Python command, some strange things could happen.  In order to
understand what can go wrong, I need to explain how the Python
completion mechanism works.

When the user requests a completion of a Python command by using TAB,
GDB will first try to determine the right set of "brkchars" that will be
used when doing the completion.  This is done by actually calling the
"complete" method of the Python class.  Then, when we already know the
"brkchars" that will be used, we call the "complete" method again, for
the same values.

If you read the thread mentioned above, you will see that one of the
design decisions was to make the "cmdpy_completer_helper" (which is the
function the does the actual calling of the "complete" method) cache the
first result of the completion, since this result will be used in the
second call, to do the actual completion.

The problem is that the "complete" command does not process the
brkchars, and the current Python completion mechanism (improved by the
patch mentioned above) relies on GDB trying to determine the brkchars,
and then doing the completion itself.  Therefore, when we use the
"complete" command instead of doing a TAB-completion on GDB, there is a
scenario where we can use the invalid cache of a previous Python command
that was completed before.  For example:

  (gdb) A <TAB>
  (gdb) complete B
  B value1
  B value10
  B value2
  B value3
  B value4
  B value5
  B value6
  B value7
  B value8
  B value9
  (gdb) B <TAB>
  comp1   comp2   comp4   comp6   comp8
  comp10  comp3   comp5   comp7   comp9

Here, we see that "complete B " gave a different result than "B <TAB>".
The reason for that is because "A <TAB>" was called before, and its
completion results were "value*", so when GDB tried to "complete B " it
wrongly answered with the results for A.  The problem here is using a
wrong cache (A's cache) for completing B.

We tried to come up with a solution that would preserve the caching
mechanism, but it wasn't really possible.  So I decided to completely
remove the cache, and doing the method calling twice for every
completion.  This is not optimal, but I do not think it will impact
users noticeably.

It is worth mentioning another small issue that I found.  The code was
doing:

  wordobj = PyUnicode_Decode (word, sizeof (word), host_charset (), NULL);

which is totally wrong, because using "sizeof" here will lead to always
the same result.  So I changed this to use "strlen".  The testcase also
catches this problem.

Keith kindly expanded the existing testcase to cover the problem
described above, and everything is passing.

gdb/ChangeLog:
2015-04-08  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR python/16699
	* python/py-cmd.c (cmdpy_completer_helper): Adjust function to not
	use a caching mechanism.  Adjust comments and code to reflect
	that.  Replace 'sizeof' by 'strlen' when fetching 'wordobj'.
	(cmdpy_completer_handle_brkchars): Adjust call to
	cmdpy_completer_helper.  Call Py_XDECREF for 'resultobj'.
	(cmdpy_completer): Likewise.

gdb/testsuite/ChangeLog:
2015-04-08  Keith Seitz  <keiths@redhat.com>

	PR python/16699
	* gdb.python/py-completion.exp: New tests for completion.
	* gdb.python/py-completion.py (CompleteLimit1): New class.
	(CompleteLimit2): Likewise.
	(CompleteLimit3): Likewise.
	(CompleteLimit4): Likewise.
	(CompleteLimit5): Likewise.
	(CompleteLimit6): Likewise.
	(CompleteLimit7): Likewise.
This commit is contained in:
Sergio Durigan Junior 2015-04-08 18:27:10 -04:00
parent f3770638ca
commit 6d62641c83
5 changed files with 227 additions and 70 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@ -1,3 +1,13 @@
2015-04-08 Sergio Durigan Junior <sergiodj@redhat.com>
PR python/16699
* python/py-cmd.c (cmdpy_completer_helper): Adjust function to not
use a caching mechanism. Adjust comments and code to reflect
that. Replace 'sizeof' by 'strlen' when fetching 'wordobj'.
(cmdpy_completer_handle_brkchars): Adjust call to
cmdpy_completer_helper. Call Py_XDECREF for 'resultobj'.
(cmdpy_completer): Likewise.
2015-04-08 Yao Qi <yao.qi@linaro.org>
* spu-tdep.c (spu_gdbarch_init): Don't call

121
gdb/python/py-cmd.c
View File

@ -210,85 +210,70 @@ cmdpy_function (struct cmd_list_element *command, char *args, int from_tty)
/* Helper function for the Python command completers (both "pure"
completer and brkchar handler). This function takes COMMAND, TEXT
and WORD and tries to call the Python method for completion with
these arguments. It also takes HANDLE_BRKCHARS_P, an argument to
identify whether it is being called from the brkchar handler or
from the "pure" completer. In the first case, it effectively calls
the Python method for completion, and records the PyObject in a
static variable (used as a "cache"). In the second case, it just
returns that variable, without actually calling the Python method
again. This saves us one Python method call.
these arguments.
The reason for this two step dance is that we need to know the set
of "brkchars" to use early on, before we actually try to perform
the completion. But if a Python command supplies a "complete"
method then we have to call that method first: it may return as its
result the kind of completion to perform and that will in turn
specify which brkchars to use. IOW, we need the result of the
"complete" method before we actually perform the completion.
This function is usually called twice: once when we are figuring out
the break characters to be used, and another to perform the real
completion itself. The reason for this two step dance is that we
need to know the set of "brkchars" to use early on, before we
actually try to perform the completion. But if a Python command
supplies a "complete" method then we have to call that method
first: it may return as its result the kind of completion to
perform and that will in turn specify which brkchars to use. IOW,
we need the result of the "complete" method before we actually
perform the completion. The only situation when this function is
not called twice is when the user uses the "complete" command: in
this scenario, there is no call to determine the "brkchars".
It is important to mention that this function is built on the
assumption that the calls to cmdpy_completer_handle_brkchars and
cmdpy_completer will be subsequent with nothing intervening. This
is true for our completer mechanism.
Ideally, it would be nice to cache the result of the first call (to
determine the "brkchars") and return this value directly in the
second call (to perform the actual completion). However, due to
the peculiarity of the "complete" command mentioned above, it is
possible to put GDB in a bad state if you perform a TAB-completion
and then a "complete"-completion sequentially. Therefore, we just
recalculate everything twice for TAB-completions.
This function returns the PyObject representing the Python method
call. */
static PyObject *
cmdpy_completer_helper (struct cmd_list_element *command,
const char *text, const char *word,
int handle_brkchars_p)
const char *text, const char *word)
{
cmdpy_object *obj = (cmdpy_object *) get_cmd_context (command);
PyObject *textobj, *wordobj;
/* This static variable will server as a "cache" for us, in order to
store the PyObject that results from calling the Python
function. */
static PyObject *resultobj = NULL;
PyObject *resultobj;
if (handle_brkchars_p)
if (obj == NULL)
error (_("Invalid invocation of Python command object."));
if (!PyObject_HasAttr ((PyObject *) obj, complete_cst))
{
/* If we were called to handle brkchars, it means this is the
first function call of two that will happen in a row.
Therefore, we need to call the completer ourselves, and cache
the return value in the static variable RESULTOBJ. Then, in
the second call, we can just use the value of RESULTOBJ to do
our job. */
if (resultobj != NULL)
Py_DECREF (resultobj);
resultobj = NULL;
if (obj == NULL)
error (_("Invalid invocation of Python command object."));
if (!PyObject_HasAttr ((PyObject *) obj, complete_cst))
{
/* If there is no complete method, don't error. */
return NULL;
}
textobj = PyUnicode_Decode (text, strlen (text), host_charset (), NULL);
if (textobj == NULL)
error (_("Could not convert argument to Python string."));
wordobj = PyUnicode_Decode (word, sizeof (word), host_charset (), NULL);
if (wordobj == NULL)
{
Py_DECREF (textobj);
error (_("Could not convert argument to Python string."));
}
resultobj = PyObject_CallMethodObjArgs ((PyObject *) obj, complete_cst,
textobj, wordobj, NULL);
Py_DECREF (textobj);
Py_DECREF (wordobj);
if (!resultobj)
{
/* Just swallow errors here. */
PyErr_Clear ();
}
Py_XINCREF (resultobj);
/* If there is no complete method, don't error. */
return NULL;
}
textobj = PyUnicode_Decode (text, strlen (text), host_charset (), NULL);
if (textobj == NULL)
error (_("Could not convert argument to Python string."));
wordobj = PyUnicode_Decode (word, strlen (word), host_charset (), NULL);
if (wordobj == NULL)
{
Py_DECREF (textobj);
error (_("Could not convert argument to Python string."));
}
resultobj = PyObject_CallMethodObjArgs ((PyObject *) obj, complete_cst,
textobj, wordobj, NULL);
Py_DECREF (textobj);
Py_DECREF (wordobj);
if (!resultobj)
{
/* Just swallow errors here. */
PyErr_Clear ();
}
Py_XINCREF (resultobj);
return resultobj;
}
@ -308,7 +293,7 @@ cmdpy_completer_handle_brkchars (struct cmd_list_element *command,
/* Calling our helper to obtain the PyObject of the Python
function. */
resultobj = cmdpy_completer_helper (command, text, word, 1);
resultobj = cmdpy_completer_helper (command, text, word);
/* Check if there was an error. */
if (resultobj == NULL)
@ -338,8 +323,7 @@ cmdpy_completer_handle_brkchars (struct cmd_list_element *command,
done:
/* We do not call Py_XDECREF here because RESULTOBJ will be used in
the subsequent call to cmdpy_completer function. */
Py_XDECREF (resultobj);
do_cleanups (cleanup);
}
@ -357,7 +341,7 @@ cmdpy_completer (struct cmd_list_element *command,
/* Calling our helper to obtain the PyObject of the Python
function. */
resultobj = cmdpy_completer_helper (command, text, word, 0);
resultobj = cmdpy_completer_helper (command, text, word);
/* If the result object of calling the Python function is NULL, it
means that there was an error. In this case, just give up and
@ -419,6 +403,7 @@ cmdpy_completer (struct cmd_list_element *command,
done:
Py_XDECREF (resultobj);
do_cleanups (cleanup);
return result;

12
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,15 @@
2015-04-08 Keith Seitz <keiths@redhat.com>
PR python/16699
* gdb.python/py-completion.exp: New tests for completion.
* gdb.python/py-completion.py (CompleteLimit1): New class.
(CompleteLimit2): Likewise.
(CompleteLimit3): Likewise.
(CompleteLimit4): Likewise.
(CompleteLimit5): Likewise.
(CompleteLimit6): Likewise.
(CompleteLimit7): Likewise.
2015-04-08 Pedro Alves <palves@redhat.com>
PR gdb/18214

65
gdb/testsuite/gdb.python/py-completion.exp
View File

@ -40,7 +40,8 @@ gdb_test_multiple "" "completefileinit completion" {
}
# Just discarding whatever we typed.
gdb_test " " ".*" "discard #1"
set discard 0
gdb_test " " ".*" "discard #[incr discard]"
# This is the problematic one.
send_gdb "completefilemethod ${testdir_complete}\t"
@ -54,7 +55,7 @@ gdb_test_multiple "" "completefilemethod completion" {
}
# Discarding again
gdb_test " " ".*" "discard #2"
gdb_test " " ".*" "discard #[incr discard]"
# Another problematic
set completion_regex "[string_to_regexp [standard_output_file "py-completion-t"]]"
@ -67,3 +68,63 @@ gdb_test_multiple "" "completefilecommandcond completion" {
pass "completefilecommandcond completion"
}
}
# Start gdb over again to clear out current state. This can interfere
# with the expected output of the below tests in a buggy gdb.
gdb_exit
gdb_start
gdb_test_no_output "source ${srcdir}/${subdir}/${testfile}.py"
gdb_test_sequence "complete completel" \
"list all completions of 'complete completel'" {
"completelimit1"
"completelimit2"
"completelimit3"
"completelimit4"
"completelimit5"
"completelimit6"
"completelimit7"
}
# Discarding again
gdb_test " " ".*" "discard #[incr discard]"
gdb_test_sequence "complete completelimit1 c" \
"list all completions of 'complete completelimit1 c'" {
"completelimit1 cl11"
"completelimit1 cl12"
"completelimit1 cl13"
}
# Discarding again
gdb_test " " ".*" "discard #[incr discard]"
# If using readline, we can TAB-complete. This used to trigger a bug
# because the cached result from the completer was being reused for
# a different python command.
if {[readline_is_used]} {
set testname "tab-complete 'completelimit1 c'"
send_gdb "completelimit1 c\t"
gdb_test_multiple "" $testname {
-re "^completelimit1 c\\\x07l1$" {
pass $testname
# Discard the command line
gdb_test " " ".*" "discard #[incr discard]"
}
}
gdb_test_sequence "complete completelimit2 c" \
"list all completions of 'complete completelimit2 c'" {
"completelimit2 cl21"
"completelimit2 cl210"
"completelimit2 cl22"
"completelimit2 cl23"
"completelimit2 cl24"
"completelimit2 cl25"
"completelimit2 cl26"
"completelimit2 cl27"
"completelimit2 cl28"
"completelimit2 cl29"
}
}

89
gdb/testsuite/gdb.python/py-completion.py
View File

@ -53,6 +53,95 @@ class CompleteFileCommandCond(gdb.Command):
else:
return gdb.COMPLETE_FILENAME
class CompleteLimit1(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit1',gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl11", "cl12", "cl13"]
class CompleteLimit2(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit2',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl21", "cl23", "cl25", "cl27", "cl29",
"cl22", "cl24", "cl26", "cl28", "cl210"]
class CompleteLimit3(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit3',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl31", "cl33", "cl35", "cl37", "cl39",
"cl32", "cl34", "cl36", "cl38", "cl310"]
class CompleteLimit4(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit4',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl41", "cl43", "cl45", "cl47", "cl49",
"cl42", "cl44", "cl46", "cl48", "cl410"]
class CompleteLimit5(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit5',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl51", "cl53", "cl55", "cl57", "cl59",
"cl52", "cl54", "cl56", "cl58", "cl510"]
class CompleteLimit6(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit6',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl61", "cl63", "cl65", "cl67", "cl69",
"cl62", "cl64", "cl66", "cl68", "cl610"]
class CompleteLimit7(gdb.Command):
def __init__(self):
gdb.Command.__init__(self,'completelimit7',
gdb.COMMAND_USER)
def invoke(self,argument,from_tty):
raise gdb.GdbError('not implemented')
def complete(self,text,word):
return ["cl71", "cl73", "cl75", "cl77", "cl79",
"cl72", "cl74", "cl76", "cl78", "cl710"]
CompleteFileInit()
CompleteFileMethod()
CompleteFileCommandCond()
CompleteLimit1()
CompleteLimit2()
CompleteLimit3()
CompleteLimit4()
CompleteLimit5()
CompleteLimit6()
CompleteLimit7()