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bdb.py
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"""Debugger basics""" import fnmatch import sys import os from inspect import CO_GENERATOR __all__ = ["BdbQuit", "Bdb", "Breakpoint"] 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. """ 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): 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): import linecache linecache.checkcache() self.botframe = None self._set_stopinfo(None, None) def trace_dispatch(self, frame, event, arg): 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): 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): # 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 & CO_GENERATOR: return self.trace_dispatch self.user_call(frame, arg) if self.quitting: raise BdbQuit return self.trace_dispatch def dispatch_return(self, frame, arg): 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 & CO_GENERATOR: 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): 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 & CO_GENERATOR 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 & CO_GENERATOR 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): for pattern in self.skip: if fnmatch.fnmatch(module_name, pattern): return True return False def stop_here(self, frame): # (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): 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): raise NotImplementedError("subclass of bdb must implement do_clear()") def break_anywhere(self, frame): 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): """This method is called when there is the remote possibility that we ever need to stop in this function.""" pass def user_line(self, frame): """This method is called when we stop or break at this line.""" pass def user_return(self, frame, return_value): """This method is called when a return trap is set here.""" pass def user_exception(self, frame, exc_info): """This method is called if an exception occurs, but only if we are to stop at or just below this level.""" pass def _set_stopinfo(self, stopframe, returnframe, stoplineno=0): 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 line no 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 & CO_GENERATOR: 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): # 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): 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 is 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): 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) def _prune_breaks(self, filename, lineno): 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): 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) def clear_bpbynumber(self, arg): try: bp = self.get_bpbynumber(arg) except ValueError as err: return str(err) bp.deleteMe() self._prune_breaks(bp.file, bp.line) def clear_all_file_breaks(self, filename): 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] def clear_all_breaks(self): if not self.breaks: return 'There are no breakpoints' for bp in Breakpoint.bpbynumber: if bp: bp.deleteMe() self.breaks = {} def get_bpbynumber(self, arg): if not arg: raise ValueError('Breakpoint number expected') try: number = int(arg) except ValueError: raise ValueError('Non-numeric breakpoint number %s' % arg) try: bp = Breakpoint.bpbynumber[number] except IndexError: raise ValueError('Breakpoint number %d out of range' % number) if bp is None: raise ValueError('Breakpoint %d already deleted' % number) return bp def get_break(self, filename, lineno): filename = self.canonic(filename) return filename in self.breaks and \ lineno in self.breaks[filename] def get_breaks(self, filename, lineno): 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): filename = self.canonic(filename) if filename in self.breaks: return self.breaks[filename] else: return [] def get_all_breaks(self): 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): 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=': '): 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>" if '__args__' in frame.f_locals: args = frame.f_locals['__args__'] else: args = None if args: s += reprlib.repr(args) else: 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): 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): 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): # B/W compatibility self.run(cmd, globals, locals) # This method is more useful to debug a single function call. def runcall(self, func, *args, **kwds): 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(): 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. """ # 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): 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): self.enabled = True def disable(self): self.enabled = False def bpprint(self, out=None): if out is None: out = sys.stdout print(self.bpformat(), file=out) def bpformat(self): 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 'breakpoint %s at %s:%s' % (self.number, self.file, self.line) # -----------end of Breakpoint class---------- def checkfuncname(b, frame): """Check whether we should break here because of `b.funcname`.""" 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 bpt at this location. Returns breakpoint that was triggered and a flag that indicates if it is ok to delete a temporary bp. """ 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)')