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"""Debugger basics""" import fnmatch import sys import os from contextlib import contextmanager 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 self.enterframe = None self._load_breaks() def canonic(self, filename): """Return canonical form of filename. For real filenames, the canonical form is a case-normalized (on case insensitive 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) @contextmanager def set_enterframe(self, frame): self.enterframe = frame yield self.enterframe = 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. """ with self.set_enterframe(frame): 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 BdbQuit 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) # The previous frame might not have f_trace set, unless we are # issuing a command that does not expect to stop, we should set # f_trace if self.stoplineno != -1: self._set_caller_tracefunc(frame) 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." if module_name is None: # some modules do not have names return False 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 def _set_caller_tracefunc(self, current_frame): # 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, unless # the caller is the botframe. caller_frame = current_frame.f_back if caller_frame and not caller_frame.f_trace and caller_frame is not self.botframe: caller_frame.f_trace = self.trace_dispatch # 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.""" 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. """ sys.settrace(None) if frame is None: frame = sys._getframe().f_back self.reset() with self.set_enterframe(frame): 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 _add_to_breaks(self, filename, lineno): """Add breakpoint to breaks, if not already there.""" bp_linenos = self.breaks.setdefault(filename, []) if lineno not in bp_linenos: bp_linenos.append(lineno) 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) self._add_to_breaks(filename, lineno) bp = Breakpoint(filename, lineno, temporary, cond, funcname) # After we set a new breakpoint, we need to search through all frames # and set f_trace to trace_dispatch if there could be a breakpoint in # that frame. frame = self.enterframe while frame: if self.break_anywhere(frame): frame.f_trace = self.trace_dispatch frame = frame.f_back return None def _load_breaks(self): """Apply all breakpoints (set in other instances) to this one. Populates this instance's breaks list from the Breakpoint class's list, which can have breakpoints set by another Bdb instance. This is necessary for interactive sessions to keep the breakpoints active across multiple calls to run(). """ for (filename, lineno) in Breakpoint.bplist.keys(): self._add_to_breaks(filename, lineno) def _prune_breaks(self, filename, lineno): """Prune breakpoints for filename: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) if lineno is not None: line = linecache.getline(filename, lineno, frame.f_globals) if line: s += lprefix + line.strip() else: s += f'{lprefix}Warning: lineno is None' 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(self, func, /, *args, **kwds): """Debug a single function call. Return the result of the function call. """ 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] @staticmethod def clearBreakpoints(): Breakpoint.next = 1 Breakpoint.bplist = {} Breakpoint.bpbynumber = [None] 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 def effective(file, line, frame): """Return (active breakpoint, delete temporary flag) or (None, None) as breakpoint to act upon. The "active breakpoint" is the first entry in bplist[line, file] (which must exist) that is enabled, for which checkfuncname is True, and that has neither a False condition nor a positive ignore count. The flag, meaning that a temporary breakpoint should be deleted, is False only when the condiion cannot be evaluated (in which case, ignore count is ignored). If no such entry exists, then (None, None) is returned. """ 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)')