bdb.py

"""Debugger basics"""

import sys
import os
import types

BdbQuit = 'bdb.BdbQuit' # 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):
        self.breaks = {}
        self.fncache = {}

    def canonic(self, filename):
        canonic = self.fncache.get(filename)
        if not canonic:
            canonic = os.path.abspath(filename)
            self.fncache[filename] = canonic
        return canonic
    
    def reset(self):
        import linecache
        linecache.checkcache()
        self.botframe = None
        self.stopframe = None
        self.returnframe = None
        self.quitting = 0
    
    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)
        print 'bdb.Bdb.dispatch: unknown debugging event:', `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
            return self.trace_dispatch
        if not (self.stop_here(frame) or self.break_anywhere(frame)):
            # No need to trace this function
            return # None
        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:
            self.user_return(frame, arg)
            if self.quitting: raise BdbQuit
    
    def dispatch_exception(self, frame, arg):
        if self.stop_here(frame):
            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 stop_here(self, frame):
        if self.stopframe is None:
            return 1
        if frame is self.stopframe:
            return 1
        while frame is not None and frame is not self.stopframe:
            if frame is self.botframe:
                return 1
            frame = frame.f_back
        return 0

    def break_here(self, frame):
        filename = self.canonic(frame.f_code.co_filename)
        if not self.breaks.has_key(filename):
            return 0
        lineno = frame.f_lineno
        if not lineno in self.breaks[filename]:
            return 0
        # 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 1
        else:
            return 0
    
    def break_anywhere(self, frame):
        return self.breaks.has_key(
            self.canonic(frame.f_code.co_filename))
    
    # 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_type, exc_value, exc_traceback)):
        """This method is called if an exception occurs,
        but only if we are to stop at or just below this level."""
        pass
    
    # Derived classes and clients can call the following methods
    # to affect the stepping state.
    
    def set_step(self):
        """Stop after one line of code."""
        self.stopframe = None
        self.returnframe = None
        self.quitting = 0
    
    def set_next(self, frame):
        """Stop on the next line in or below the given frame."""
        self.stopframe = frame
        self.returnframe = None
        self.quitting = 0
    
    def set_return(self, frame):
        """Stop when returning from the given frame."""
        self.stopframe = frame.f_back
        self.returnframe = frame
        self.quitting = 0
    
    def set_trace(self):
        """Start debugging from here."""
        try:
            1 + ''
        except:
            frame = sys.exc_info()[2].tb_frame.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.stopframe = self.botframe
        self.returnframe = None
        self.quitting = 0
        if not self.breaks:
            # no breakpoints; run without debugger overhead
            sys.settrace(None)
            try:
                1 + ''  # raise an exception
            except:
                frame = sys.exc_info()[2].tb_frame.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 = 1
        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=0, cond = 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)
        if not self.breaks.has_key(filename):
            self.breaks[filename] = []
        list = self.breaks[filename]
        if not lineno in list:
            list.append(lineno)
        bp = Breakpoint(filename, lineno, temporary, cond)

    def clear_break(self, filename, lineno):
        filename = self.canonic(filename)
        if not self.breaks.has_key(filename):
            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()
        if not Breakpoint.bplist.has_key((filename, lineno)):
            self.breaks[filename].remove(lineno)
        if not self.breaks[filename]:
            del self.breaks[filename]
    
    def clear_bpbynumber(self, arg):
        try:
            number = int(arg)
        except:
            return 'Non-numeric breakpoint number (%s)' % arg
        try:
            bp = Breakpoint.bpbynumber[number]
        except IndexError:
            return 'Breakpoint number (%d) out of range' % number
        if not bp:
            return 'Breakpoint (%d) already deleted' % number
        self.clear_break(bp.file, bp.line)

    def clear_all_file_breaks(self, filename):
        filename = self.canonic(filename)
        if not self.breaks.has_key(filename):
            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_break(self, filename, lineno):
        filename = self.canonic(filename)
        return self.breaks.has_key(filename) and \
            lineno in self.breaks[filename]
    
    def get_breaks(self, filename, lineno):
        filename = self.canonic(filename)
        return self.breaks.has_key(filename) and \
            lineno in self.breaks[filename] and \
            Breakpoint.bplist[filename, lineno] or []
    
    def get_file_breaks(self, filename):
        filename = self.canonic(filename)
        if self.breaks.has_key(filename):
            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
        return stack, i
    
    # 
    
    def format_stack_entry(self, frame_lineno, lprefix=': '):
        import linecache, repr, string
        frame, lineno = frame_lineno
        filename = self.canonic(frame.f_code.co_filename)
        s = filename + '(' + `lineno` + ')'
        if frame.f_code.co_name:
            s = s + frame.f_code.co_name
        else:
            s = s + "<lambda>"
        if frame.f_locals.has_key('__args__'):
            args = frame.f_locals['__args__']
        else:
            args = None
        if args:
            s = s + repr.repr(args)
        else:
            s = s + '()'
        if frame.f_locals.has_key('__return__'):
            rv = frame.f_locals['__return__']
            s = s + '->'
            s = s + repr.repr(rv)
        line = linecache.getline(filename, lineno)
        if line: s = s + lprefix + string.strip(line)
        return s
    
    # The following two methods can be called by clients to use
    # a debugger to debug a statement, given as a string.
    
    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()
        sys.settrace(self.trace_dispatch)
        if not isinstance(cmd, types.CodeType):
            cmd = cmd+'\n'
        try:
            try:
                exec cmd in globals, locals
            except BdbQuit:
                pass
        finally:
            self.quitting = 1
            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)
        if not isinstance(expr, types.CodeType):
            expr = expr+'\n'
        try:
            try:
                return eval(expr, globals, locals)
            except BdbQuit:
                pass
        finally:
            self.quitting = 1
            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):
        self.reset()
        sys.settrace(self.trace_dispatch)
        res = None
        try:
            try:
                res = apply(func, args)
            except BdbQuit:
                pass
        finally:
            self.quitting = 1
            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=0, cond = None):
        self.file = file    # This better be in canonical form!
        self.line = line
        self.temporary = temporary
        self.cond = cond
        self.enabled = 1
        self.ignore = 0
        self.hits = 0
        self.number = Breakpoint.next
        Breakpoint.next = Breakpoint.next + 1
        # Build the two lists
        self.bpbynumber.append(self)
        if self.bplist.has_key((file, line)):
            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 = 1

    def disable(self):
        self.enabled = 0

    def bpprint(self):
        if self.temporary:
           disp = 'del  '
        else:
           disp = 'keep '
        if self.enabled:
           disp = disp + 'yes'
        else:
           disp = disp + 'no '
        print '%-4dbreakpoint    %s at %s:%d' % (self.number, disp,
                             self.file, self.line)
        if self.cond:
            print '\tstop only if %s' % (self.cond,)
        if self.ignore:
            print '\tignore next %d hits' % (self.ignore)
        if (self.hits):
            if (self.hits > 1): ss = 's'
            else: ss = ''
            print ('\tbreakpoint already hit %d time%s' %
                   (self.hits, ss))

# -----------end of Breakpoint class----------

# 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 i in range(0, len(possibles)):
        b = possibles[i]
        if b.enabled == 0:
            continue
        # Count every hit when bp is enabled
        b.hits = b.hits + 1
        if not b.cond:
            # If unconditional, and ignoring,
            # go on to next, else break
            if b.ignore > 0:
                b.ignore = b.ignore -1
                continue
            else:
                # breakpoint and marker that's ok
                # to delete if temporary
                return (b,1)
        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 = b.ignore -1
                        # continue
                    else:
                        return (b,1)
                # 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,0)
    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, string
        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)
        print '+++', fn, frame.f_lineno, name, ':', string.strip(line)
    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)')