"""Debugger basics"""
import fnmatch
import sys
import os
from inspect import CO_GENERATOR, CO_COROUTINE, CO_ASYNC_GENERATOR
__all__ = ["BdbQuit", "Bdb", "Breakpoint"]
GENERATOR_AND_COROUTINE_FLAGS = CO_GENERATOR | CO_COROUTINE | CO_ASYNC_GENERATOR
class BdbQuit(Exception):
"""Exception to give up completely."""
class Bdb:
"""Generic Python debugger base class.
This class takes care of details of the trace facility;
a derived class should implement user interaction.
The standard debugger class (pdb.Pdb) is an example.
The optional skip argument must be an iterable of glob-style
module name patterns. The debugger will not step into frames
that originate in a module that matches one of these patterns.
Whether a frame is considered to originate in a certain module
is determined by the __name__ in the frame globals.
"""
def __init__(self, skip=None):
self.skip = set(skip) if skip else None
self.breaks = {}
self.fncache = {}
self.frame_returning = None
def canonic(self, filename):
"""Return canonical form of filename.
For real filenames, the canonical form is a case-normalized (on
case insenstive filesystems) absolute path. 'Filenames' with
angle brackets, such as "<stdin>", generated in interactive
mode, are returned unchanged.
"""
if filename == "<" + filename[1:-1] + ">":
return filename
canonic = self.fncache.get(filename)
if not canonic:
canonic = os.path.abspath(filename)
canonic = os.path.normcase(canonic)
self.fncache[filename] = canonic
return canonic
def reset(self):
"""Set values of attributes as ready to start debugging."""
import linecache
linecache.checkcache()
self.botframe = None
self._set_stopinfo(None, None)
def trace_dispatch(self, frame, event, arg):
"""Dispatch a trace function for debugged frames based on the event.
This function is installed as the trace function for debugged
frames. Its return value is the new trace function, which is
usually itself. The default implementation decides how to
dispatch a frame, depending on the type of event (passed in as a
string) that is about to be executed.
The event can be one of the following:
line: A new line of code is going to be executed.
call: A function is about to be called or another code block
is entered.
return: A function or other code block is about to return.
exception: An exception has occurred.
c_call: A C function is about to be called.
c_return: A C function has returned.
c_exception: A C function has raised an exception.
For the Python events, specialized functions (see the dispatch_*()
methods) are called. For the C events, no action is taken.
The arg parameter depends on the previous event.
"""
if self.quitting:
return # None
if event == 'line':
return self.dispatch_line(frame)
if event == 'call':
return self.dispatch_call(frame, arg)
if event == 'return':
return self.dispatch_return(frame, arg)
if event == 'exception':
return self.dispatch_exception(frame, arg)
if event == 'c_call':
return self.trace_dispatch
if event == 'c_exception':
return self.trace_dispatch
if event == 'c_return':
return self.trace_dispatch
print('bdb.Bdb.dispatch: unknown debugging event:', repr(event))
return self.trace_dispatch
def dispatch_line(self, frame):
"""Invoke user function and return trace function for line event.
If the debugger stops on the current line, invoke
self.user_line(). Raise BdbQuit if self.quitting is set.
Return self.trace_dispatch to continue tracing in this scope.
"""
if self.stop_here(frame) or self.break_here(frame):
self.user_line(frame)
if self.quitting: raise BdbQuit
return self.trace_dispatch
def dispatch_call(self, frame, arg):
"""Invoke user function and return trace function for call event.
If the debugger stops on this function call, invoke
self.user_call(). Raise BbdQuit if self.quitting is set.
Return self.trace_dispatch to continue tracing in this scope.
"""
# XXX 'arg' is no longer used
if self.botframe is None:
# First call of dispatch since reset()
self.botframe = frame.f_back # (CT) Note that this may also be None!
return self.trace_dispatch
if not (self.stop_here(frame) or self.break_anywhere(frame)):
# No need to trace this function
return # None
# Ignore call events in generator except when stepping.
if self.stopframe and frame.f_code.co_flags & GENERATOR_AND_COROUTINE_FLAGS:
return self.trace_dispatch
self.user_call(frame, arg)
if self.quitting: raise BdbQuit
return self.trace_dispatch
def dispatch_return(self, frame, arg):
"""Invoke user function and return trace function for return event.
If the debugger stops on this function return, invoke
self.user_return(). Raise BdbQuit if self.quitting is set.
Return self.trace_dispatch to continue tracing in this scope.
"""
if self.stop_here(frame) or frame == self.returnframe:
# Ignore return events in generator except when stepping.
if self.stopframe and frame.f_code.co_flags & GENERATOR_AND_COROUTINE_FLAGS:
return self.trace_dispatch
try:
self.frame_returning = frame
self.user_return(frame, arg)
finally:
self.frame_returning = None
if self.quitting: raise BdbQuit
# The user issued a 'next' or 'until' command.
if self.stopframe is frame and self.stoplineno != -1:
self._set_stopinfo(None, None)
return self.trace_dispatch
def dispatch_exception(self, frame, arg):
"""Invoke user function and return trace function for exception event.
If the debugger stops on this exception, invoke
self.user_exception(). Raise BdbQuit if self.quitting is set.
Return self.trace_dispatch to continue tracing in this scope.
"""
if self.stop_here(frame):
# When stepping with next/until/return in a generator frame, skip
# the internal StopIteration exception (with no traceback)
# triggered by a subiterator run with the 'yield from' statement.
if not (frame.f_code.co_flags & GENERATOR_AND_COROUTINE_FLAGS
and arg[0] is StopIteration and arg[2] is None):
self.user_exception(frame, arg)
if self.quitting: raise BdbQuit
# Stop at the StopIteration or GeneratorExit exception when the user
# has set stopframe in a generator by issuing a return command, or a
# next/until command at the last statement in the generator before the
# exception.
elif (self.stopframe and frame is not self.stopframe
and self.stopframe.f_code.co_flags & GENERATOR_AND_COROUTINE_FLAGS
and arg[0] in (StopIteration, GeneratorExit)):
self.user_exception(frame, arg)
if self.quitting: raise BdbQuit
return self.trace_dispatch
# Normally derived classes don't override the following
# methods, but they may if they want to redefine the
# definition of stopping and breakpoints.
def is_skipped_module(self, module_name):
"Return True if module_name matches any skip pattern."
for pattern in self.skip:
if fnmatch.fnmatch(module_name, pattern):
return True
return False
def stop_here(self, frame):
"Return True if frame is below the starting frame in the stack."
# (CT) stopframe may now also be None, see dispatch_call.
# (CT) the former test for None is therefore removed from here.
if self.skip and \
self.is_skipped_module(frame.f_globals.get('__name__')):
return False
if frame is self.stopframe:
if self.stoplineno == -1:
return False
return frame.f_lineno >= self.stoplineno
if not self.stopframe:
return True
return False
def break_here(self, frame):
"""Return True if there is an effective breakpoint for this line.
Check for line or function breakpoint and if in effect.
Delete temporary breakpoints if effective() says to.
"""
filename = self.canonic(frame.f_code.co_filename)
if filename not in self.breaks:
return False
lineno = frame.f_lineno
if lineno not in self.breaks[filename]:
# The line itself has no breakpoint, but maybe the line is the
# first line of a function with breakpoint set by function name.
lineno = frame.f_code.co_firstlineno
if lineno not in self.breaks[filename]:
return False
# flag says ok to delete temp. bp
(bp, flag) = effective(filename, lineno, frame)
if bp:
self.currentbp = bp.number
if (flag and bp.temporary):
self.do_clear(str(bp.number))
return True
else:
return False
def do_clear(self, arg):
"""Remove temporary breakpoint.
Must implement in derived classes or get NotImplementedError.
"""
raise NotImplementedError("subclass of bdb must implement do_clear()")
def break_anywhere(self, frame):
"""Return True if there is any breakpoint for frame's filename.
"""
return self.canonic(frame.f_code.co_filename) in self.breaks
# Derived classes should override the user_* methods
# to gain control.
def user_call(self, frame, argument_list):
"""Called if we might stop in a function."""
pass
def user_line(self, frame):
"""Called when we stop or break at a line."""
pass
def user_return(self, frame, return_value):
"""Called when a return trap is set here."""
pass
def user_exception(self, frame, exc_info):
"""Called when we stop on an exception."""
pass
def _set_stopinfo(self, stopframe, returnframe, stoplineno=0):
"""Set the attributes for stopping.
If stoplineno is greater than or equal to 0, then stop at line
greater than or equal to the stopline. If stoplineno is -1, then
don't stop at all.
"""
self.stopframe = stopframe
self.returnframe = returnframe
self.quitting = False
# stoplineno >= 0 means: stop at line >= the stoplineno
# stoplineno -1 means: don't stop at all
self.stoplineno = stoplineno
# Derived classes and clients can call the following methods
# to affect the stepping state.
def set_until(self, frame, lineno=None):
"""Stop when the line with the lineno greater than the current one is
reached or when returning from current frame."""
# the name "until" is borrowed from gdb
if lineno is None:
lineno = frame.f_lineno + 1
self._set_stopinfo(frame, frame, lineno)
def set_step(self):
"""Stop after one line of code."""
# Issue #13183: pdb skips frames after hitting a breakpoint and running
# step commands.
# Restore the trace function in the caller (that may not have been set
# for performance reasons) when returning from the current frame.
if self.frame_returning:
caller_frame = self.frame_returning.f_back
if caller_frame and not caller_frame.f_trace:
caller_frame.f_trace = self.trace_dispatch
self._set_stopinfo(None, None)
def set_next(self, frame):
"""Stop on the next line in or below the given frame."""
self._set_stopinfo(frame, None)
def set_return(self, frame):
"""Stop when returning from the given frame."""
if frame.f_code.co_flags & GENERATOR_AND_COROUTINE_FLAGS:
self._set_stopinfo(frame, None, -1)
else:
self._set_stopinfo(frame.f_back, frame)
def set_trace(self, frame=None):
"""Start debugging from frame.
If frame is not specified, debugging starts from caller's frame.
"""
if frame is None:
frame = sys._getframe().f_back
self.reset()
while frame:
frame.f_trace = self.trace_dispatch
self.botframe = frame
frame = frame.f_back
self.set_step()
sys.settrace(self.trace_dispatch)
def set_continue(self):
"""Stop only at breakpoints or when finished.
If there are no breakpoints, set the system trace function to None.
"""
# Don't stop except at breakpoints or when finished
self._set_stopinfo(self.botframe, None, -1)
if not self.breaks:
# no breakpoints; run without debugger overhead
sys.settrace(None)
frame = sys._getframe().f_back
while frame and frame is not self.botframe:
del frame.f_trace
frame = frame.f_back
def set_quit(self):
"""Set quitting attribute to True.
Raises BdbQuit exception in the next call to a dispatch_*() method.
"""
self.stopframe = self.botframe
self.returnframe = None
self.quitting = True
sys.settrace(None)
# Derived classes and clients can call the following methods
# to manipulate breakpoints. These methods return an
# error message if something went wrong, None if all is well.
# Set_break prints out the breakpoint line and file:lineno.
# Call self.get_*break*() to see the breakpoints or better
# for bp in Breakpoint.bpbynumber: if bp: bp.bpprint().
def set_break(self, filename, lineno, temporary=False, cond=None,
funcname=None):
"""Set a new breakpoint for filename:lineno.
If lineno doesn't exist for the filename, return an error message.
The filename should be in canonical form.
"""
filename = self.canonic(filename)
import linecache # Import as late as possible
line = linecache.getline(filename, lineno)
if not line:
return 'Line %s:%d does not exist' % (filename, lineno)
list = self.breaks.setdefault(filename, [])
if lineno not in list:
list.append(lineno)
bp = Breakpoint(filename, lineno, temporary, cond, funcname)
return None
def _prune_breaks(self, filename, lineno):
"""Prune breakpoints for filname:lineno.
A list of breakpoints is maintained in the Bdb instance and in
the Breakpoint class. If a breakpoint in the Bdb instance no
longer exists in the Breakpoint class, then it's removed from the
Bdb instance.
"""
if (filename, lineno) not in Breakpoint.bplist:
self.breaks[filename].remove(lineno)
if not self.breaks[filename]:
del self.breaks[filename]
def clear_break(self, filename, lineno):
"""Delete breakpoints for filename:lineno.
If no breakpoints were set, return an error message.
"""
filename = self.canonic(filename)
if filename not in self.breaks:
return 'There are no breakpoints in %s' % filename
if lineno not in self.breaks[filename]:
return 'There is no breakpoint at %s:%d' % (filename, lineno)
# If there's only one bp in the list for that file,line
# pair, then remove the breaks entry
for bp in Breakpoint.bplist[filename, lineno][:]:
bp.deleteMe()
self._prune_breaks(filename, lineno)
return None
def clear_bpbynumber(self, arg):
"""Delete a breakpoint by its index in Breakpoint.bpbynumber.
If arg is invalid, return an error message.
"""
try:
bp = self.get_bpbynumber(arg)
except ValueError as err:
return str(err)
bp.deleteMe()
self._prune_breaks(bp.file, bp.line)
return None
def clear_all_file_breaks(self, filename):
"""Delete all breakpoints in filename.
If none were set, return an error message.
"""
filename = self.canonic(filename)
if filename not in self.breaks:
return 'There are no breakpoints in %s' % filename
for line in self.breaks[filename]:
blist = Breakpoint.bplist[filename, line]
for bp in blist:
bp.deleteMe()
del self.breaks[filename]
return None
def clear_all_breaks(self):
"""Delete all existing breakpoints.
If none were set, return an error message.
"""
if not self.breaks:
return 'There are no breakpoints'
for bp in Breakpoint.bpbynumber:
if bp:
bp.deleteMe()
self.breaks = {}
return None
def get_bpbynumber(self, arg):
"""Return a breakpoint by its index in Breakpoint.bybpnumber.
For invalid arg values or if the breakpoint doesn't exist,
raise a ValueError.
"""
if not arg:
raise ValueError('Breakpoint number expected')
try:
number = int(arg)
except ValueError:
raise ValueError('Non-numeric breakpoint number %s' % arg) from None
try:
bp = Breakpoint.bpbynumber[number]
except IndexError:
raise ValueError('Breakpoint number %d out of range' % number) from None
if bp is None:
raise ValueError('Breakpoint %d already deleted' % number)
return bp
def get_break(self, filename, lineno):
"""Return True if there is a breakpoint for filename:lineno."""
filename = self.canonic(filename)
return filename in self.breaks and \
lineno in self.breaks[filename]
def get_breaks(self, filename, lineno):
"""Return all breakpoints for filename:lineno.
If no breakpoints are set, return an empty list.
"""
filename = self.canonic(filename)
return filename in self.breaks and \
lineno in self.breaks[filename] and \
Breakpoint.bplist[filename, lineno] or []
def get_file_breaks(self, filename):
"""Return all lines with breakpoints for filename.
If no breakpoints are set, return an empty list.
"""
filename = self.canonic(filename)
if filename in self.breaks:
return self.breaks[filename]
else:
return []
def get_all_breaks(self):
"""Return all breakpoints that are set."""
return self.breaks
# Derived classes and clients can call the following method
# to get a data structure representing a stack trace.
def get_stack(self, f, t):
"""Return a list of (frame, lineno) in a stack trace and a size.
List starts with original calling frame, if there is one.
Size may be number of frames above or below f.
"""
stack = []
if t and t.tb_frame is f:
t = t.tb_next
while f is not None:
stack.append((f, f.f_lineno))
if f is self.botframe:
break
f = f.f_back
stack.reverse()
i = max(0, len(stack) - 1)
while t is not None:
stack.append((t.tb_frame, t.tb_lineno))
t = t.tb_next
if f is None:
i = max(0, len(stack) - 1)
return stack, i
def format_stack_entry(self, frame_lineno, lprefix=': '):
"""Return a string with information about a stack entry.
The stack entry frame_lineno is a (frame, lineno) tuple. The
return string contains the canonical filename, the function name
or '<lambda>', the input arguments, the return value, and the
line of code (if it exists).
"""
import linecache, reprlib
frame, lineno = frame_lineno
filename = self.canonic(frame.f_code.co_filename)
s = '%s(%r)' % (filename, lineno)
if frame.f_code.co_name:
s += frame.f_code.co_name
else:
s += "<lambda>"
s += '()'
if '__return__' in frame.f_locals:
rv = frame.f_locals['__return__']
s += '->'
s += reprlib.repr(rv)
line = linecache.getline(filename, lineno, frame.f_globals)
if line:
s += lprefix + line.strip()
return s
# The following methods can be called by clients to use
# a debugger to debug a statement or an expression.
# Both can be given as a string, or a code object.
def run(self, cmd, globals=None, locals=None):
"""Debug a statement executed via the exec() function.
globals defaults to __main__.dict; locals defaults to globals.
"""
if globals is None:
import __main__
globals = __main__.__dict__
if locals is None:
locals = globals
self.reset()
if isinstance(cmd, str):
cmd = compile(cmd, "<string>", "exec")
sys.settrace(self.trace_dispatch)
try:
exec(cmd, globals, locals)
except BdbQuit:
pass
finally:
self.quitting = True
sys.settrace(None)
def runeval(self, expr, globals=None, locals=None):
"""Debug an expression executed via the eval() function.
globals defaults to __main__.dict; locals defaults to globals.
"""
if globals is None:
import __main__
globals = __main__.__dict__
if locals is None:
locals = globals
self.reset()
sys.settrace(self.trace_dispatch)
try:
return eval(expr, globals, locals)
except BdbQuit:
pass
finally:
self.quitting = True
sys.settrace(None)
def runctx(self, cmd, globals, locals):
"""For backwards-compatibility. Defers to run()."""
# B/W compatibility
self.run(cmd, globals, locals)
# This method is more useful to debug a single function call.
def runcall(*args, **kwds):
"""Debug a single function call.
Return the result of the function call.
"""
if len(args) >= 2:
self, func, *args = args
elif not args:
raise TypeError("descriptor 'runcall' of 'Bdb' object "
"needs an argument")
elif 'func' in kwds:
func = kwds.pop('func')
self, *args = args
else:
raise TypeError('runcall expected at least 1 positional argument, '
'got %d' % (len(args)-1))
self.reset()
sys.settrace(self.trace_dispatch)
res = None
try:
res = func(*args, **kwds)
except BdbQuit:
pass
finally:
self.quitting = True
sys.settrace(None)
return res
def set_trace():
"""Start debugging with a Bdb instance from the caller's frame."""
Bdb().set_trace()
class Breakpoint:
"""Breakpoint class.
Implements temporary breakpoints, ignore counts, disabling and
(re)-enabling, and conditionals.
Breakpoints are indexed by number through bpbynumber and by
the (file, line) tuple using bplist. The former points to a
single instance of class Breakpoint. The latter points to a
list of such instances since there may be more than one
breakpoint per line.
When creating a breakpoint, its associated filename should be
in canonical form. If funcname is defined, a breakpoint hit will be
counted when the first line of that function is executed. A
conditional breakpoint always counts a hit.
"""
# XXX Keeping state in the class is a mistake -- this means
# you cannot have more than one active Bdb instance.
next = 1 # Next bp to be assigned
bplist = {} # indexed by (file, lineno) tuple
bpbynumber = [None] # Each entry is None or an instance of Bpt
# index 0 is unused, except for marking an
# effective break .... see effective()
def __init__(self, file, line, temporary=False, cond=None, funcname=None):
self.funcname = funcname
# Needed if funcname is not None.
self.func_first_executable_line = None
self.file = file # This better be in canonical form!
self.line = line
self.temporary = temporary
self.cond = cond
self.enabled = True
self.ignore = 0
self.hits = 0
self.number = Breakpoint.next
Breakpoint.next += 1
# Build the two lists
self.bpbynumber.append(self)
if (file, line) in self.bplist:
self.bplist[file, line].append(self)
else:
self.bplist[file, line] = [self]
def deleteMe(self):
"""Delete the breakpoint from the list associated to a file:line.
If it is the last breakpoint in that position, it also deletes
the entry for the file:line.
"""
index = (self.file, self.line)
self.bpbynumber[self.number] = None # No longer in list
self.bplist[index].remove(self)
if not self.bplist[index]:
# No more bp for this f:l combo
del self.bplist[index]
def enable(self):
"""Mark the breakpoint as enabled."""
self.enabled = True
def disable(self):
"""Mark the breakpoint as disabled."""
self.enabled = False
def bpprint(self, out=None):
"""Print the output of bpformat().
The optional out argument directs where the output is sent
and defaults to standard output.
"""
if out is None:
out = sys.stdout
print(self.bpformat(), file=out)
def bpformat(self):
"""Return a string with information about the breakpoint.
The information includes the breakpoint number, temporary
status, file:line position, break condition, number of times to
ignore, and number of times hit.
"""
if self.temporary:
disp = 'del '
else:
disp = 'keep '
if self.enabled:
disp = disp + 'yes '
else:
disp = disp + 'no '
ret = '%-4dbreakpoint %s at %s:%d' % (self.number, disp,
self.file, self.line)
if self.cond:
ret += '\n\tstop only if %s' % (self.cond,)
if self.ignore:
ret += '\n\tignore next %d hits' % (self.ignore,)
if self.hits:
if self.hits > 1:
ss = 's'
else:
ss = ''
ret += '\n\tbreakpoint already hit %d time%s' % (self.hits, ss)
return ret
def __str__(self):
"Return a condensed description of the breakpoint."
return 'breakpoint %s at %s:%s' % (self.number, self.file, self.line)
# -----------end of Breakpoint class----------
def checkfuncname(b, frame):
"""Return True if break should happen here.
Whether a break should happen depends on the way that b (the breakpoint)
was set. If it was set via line number, check if b.line is the same as
the one in the frame. If it was set via function name, check if this is
the right function and if it is on the first executable line.
"""
if not b.funcname:
# Breakpoint was set via line number.
if b.line != frame.f_lineno:
# Breakpoint was set at a line with a def statement and the function
# defined is called: don't break.
return False
return True
# Breakpoint set via function name.
if frame.f_code.co_name != b.funcname:
# It's not a function call, but rather execution of def statement.
return False
# We are in the right frame.
if not b.func_first_executable_line:
# The function is entered for the 1st time.
b.func_first_executable_line = frame.f_lineno
if b.func_first_executable_line != frame.f_lineno:
# But we are not at the first line number: don't break.
return False
return True
# Determines if there is an effective (active) breakpoint at this
# line of code. Returns breakpoint number or 0 if none
def effective(file, line, frame):
"""Determine which breakpoint for this file:line is to be acted upon.
Called only if we know there is a breakpoint at this location. Return
the breakpoint that was triggered and a boolean that indicates if it is
ok to delete a temporary breakpoint. Return (None, None) if there is no
matching breakpoint.
"""
possibles = Breakpoint.bplist[file, line]
for b in possibles:
if not b.enabled:
continue
if not checkfuncname(b, frame):
continue
# Count every hit when bp is enabled
b.hits += 1
if not b.cond:
# If unconditional, and ignoring go on to next, else break
if b.ignore > 0:
b.ignore -= 1
continue
else:
# breakpoint and marker that it's ok to delete if temporary
return (b, True)
else:
# Conditional bp.
# Ignore count applies only to those bpt hits where the
# condition evaluates to true.
try:
val = eval(b.cond, frame.f_globals, frame.f_locals)
if val:
if b.ignore > 0:
b.ignore -= 1
# continue
else:
return (b, True)
# else:
# continue
except:
# if eval fails, most conservative thing is to stop on
# breakpoint regardless of ignore count. Don't delete
# temporary, as another hint to user.
return (b, False)
return (None, None)
# -------------------- testing --------------------
class Tdb(Bdb):
def user_call(self, frame, args):
name = frame.f_code.co_name
if not name: name = '???'
print('+++ call', name, args)
def user_line(self, frame):
import linecache
name = frame.f_code.co_name
if not name: name = '???'
fn = self.canonic(frame.f_code.co_filename)
line = linecache.getline(fn, frame.f_lineno, frame.f_globals)
print('+++', fn, frame.f_lineno, name, ':', line.strip())
def user_return(self, frame, retval):
print('+++ return', retval)
def user_exception(self, frame, exc_stuff):
print('+++ exception', exc_stuff)
self.set_continue()
def foo(n):
print('foo(', n, ')')
x = bar(n*10)
print('bar returned', x)
def bar(a):
print('bar(', a, ')')
return a/2
def test():
t = Tdb()
t.run('import bdb; bdb.foo(10)')
