Library import 16 (#2433)

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1 files changed, 893 insertions, 0 deletions

diff --git a/contrib/tools/python3/Lib/bdb.py b/contrib/tools/python3/Lib/bdb.py
new file mode 100644
index 0000000000..0f3eec653b
--- /dev/null
+++ b/contrib/tools/python3/Lib/bdb.py
@@ -0,0 +1,893 @@
+"""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
+
+        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)
+
+    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 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)
+        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
+
+    # 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 _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)
+        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)')