Syntax error, script doesn't work

[allopislozano]

When I include the file in .gdbinit I get the following message:

File "/home/allopis/.gdb/gdb-colour-filter/colour_filter.py", line 21
    def __init__(self, *args, depth=0, **kwargs):
                                  ^
SyntaxError: invalid syntax

Regards!

[allopislozano]

Looks like *args must be after depth parameter. After fixing that, I get a new error:

  File "/home/allopis/.gdb/gdb-colour-filter/colour_filter.py", line 158
    def __init__(self, frames: Iterator[Frame]):

Does this script require python3? my system uses python2 by default. If that's the issue, how can I tell gdb which python interpreter to use?

[daskol]

Yes, the script requires python 3.5+. It has internally used type hinting. The main reason why I prefer to use the latest python is that python 2 is deprecated and will not be supported since 2020. I highly recommend you to migrate from python 2 to 3.

Unfortunately, python embedded to gdb as a shared library (check with ldd /usr/bin/gdb). It means that you could not change version of interpreter without recompilation of gdb. Try to apply the patch below. It should solve your issue.

diff --git a/colour_filter.py b/colour_filter.py
index 3de0a5b..fbd7deb 100644
--- a/colour_filter.py
+++ b/colour_filter.py
@@ -2,10 +2,8 @@
 #   encoding: utf8
 #   file: colour_filter.py
 
-from typing import Iterator, Text
-
 from gdb import parameter as get_parameter
-from gdb import Frame, frame_filters, execute
+from gdb import frame_filters, execute
 from gdb.FrameDecorator import FrameDecorator
 
 
@@ -18,10 +16,10 @@ class FrameColorizer(FrameDecorator):
     Notes: There is not special support Frame.elided() property.
     """
 
-    def __init__(self, *args, depth=0, **kwargs):
+    def __init__(self, *args, **kwargs):
         super(FrameColorizer, self).__init__(*args, **kwargs)
 
-        self._depth = depth
+        self._depth = kwargs.get(depth, 0)
         self.frame = super(FrameColorizer, self).inferior_frame()
 
     def __str__(self):
@@ -93,7 +91,7 @@ class FrameColorizer(FrameDecorator):
             # Here we have something like
             # > raise + 272 in section .text of /usr/lib/libc.so.6
             # XXX: gdb.find_pc_line
-            symbol = gdb.execute('info symbol 0x%016x' % func, False, True)
+            symbol = execute('info symbol 0x%016x' % func, False, True)
 
             # But here we truncate layout in binary
             # > raise + 272
@@ -154,7 +152,7 @@ class FilterProxy:
     properly on the first and the sole call.
     """
 
-    def __init__(self, frames: Iterator[Frame]):
+    def __init__(self, frames):
         self.frames = (FrameColorizer(frame, depth=ix)
                        for ix, frame in enumerate(frames))
 
@@ -189,7 +187,7 @@ class ColourFilter:
         # dictionary.
         frame_filters[self.name] = self
 
-    def filter(self, iters: Iterator[Frame]) -> Iterator[Frame]:
+    def filter(self, iters):
         return FilterProxy(iters)
 
 

[allopislozano]

After applying the patch, it looks like some color is there... for example $gdb prompt is shown in red, but when I try to show a backtrace I get this:
Python Exception <type 'exceptions.TypeError'> instance has no next() method:
And I cannot see the frames unfortunately :/

[daskol]

Sorry for so long delay. Try to apply the patch below. The reason is that iterator protocol differs between Python 2 and Python 3.

diff --git a/colour_filter.py b/colour_filter.py
index 2970f2a..bddf1d0 100644
--- a/colour_filter.py
+++ b/colour_filter.py
@@ -163,6 +163,9 @@ class FilterProxy:
         return self
 
     def __next__(self):
+        return self.next()
+
+    def next(self):
         self.unroll_stack()
         raise StopIteration
 

[ryanmiao]

Sorry for so long delay. Try to apply the patch below. The reason is that iterator protocol differs between Python 2 and Python 3.

diff --git a/colour_filter.py b/colour_filter.py
index 2970f2a..bddf1d0 100644
--- a/colour_filter.py
+++ b/colour_filter.py
@@ -163,6 +163,9 @@ class FilterProxy:
         return self
 
     def __next__(self):
+        return self.next()
+
+    def next(self):
         self.unroll_stack()
         raise StopIteration
 

hi Dan, after apply this patch, the bt also got an error:

Python Exception <type 'exceptions.TypeError'> init() got an unexpected keyword argument 'depth':

[daskol]

@ryanmiao GDB Python API was changed a bit. So, this patch should be usefull if you have applied the previous two.

diff --git a/colour_filter.py b/colour_filter.py
index d5b070d..74f5b92 100644
--- a/colour_filter.py
+++ b/colour_filter.py
@@ -16,10 +16,10 @@ class FrameColorizer(FrameDecorator):
     Notes: There is not special support Frame.elided() property.
     """
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args, depth=0, **kwargs):
         super(FrameColorizer, self).__init__(*args, **kwargs)
 
-        self._depth = kwargs.get(depth, 0)
+        self._depth = depth
         self.frame = super(FrameColorizer, self).inferior_frame()
 
     def __str__(self):

Also, it would be better to use Python 3 with GDB since Python 2 is deprecated.

[maksimovichsam]

I was facing some issues with Python 2 even after all these patches, but I fixed them and got colored backtrace to work with the file below, for those still facing issues.

#!/usr/bin/env gdb
#   encoding: utf8
#   file: colour_filter.py

from gdb import parameter as get_parameter
from gdb import frame_filters, execute
from gdb.FrameDecorator import FrameDecorator


class FrameColorizer(FrameDecorator):
    """FrameColorizer repeats all actions to get all common frame attribute and
    then spices a bit output with colours. Format of output string is following.

    #<depth> <address> in <function> (<frame_args>) at <filename>[:<line>]

    Notes: There is not special support Frame.elided() property.
    """

    def __init__(self, frame, depth=0):
        super(FrameColorizer, self).__init__(frame)

        self._depth = depth
        self.frame = super(FrameColorizer, self).inferior_frame()

    def __str__(self):
        is_print_address = get_parameter('print address')

        part1 = self.depth()
        part2 = self.function() + ' \033[1;37m(' + self.frame_args() + ')\033[0m'
        part3 = self.filename() + self.line()

        if is_print_address:
            part1 += '  ' + self.address() + ' in '
        else:
            part1 += ' '

        parts = part1 + part2 + ' at ' + part3

        screen_width = self.get_screen_width()
        if screen_width is not None and len(parts) > screen_width:
            shift_width = int(self.length(part1)) - 1
            shift_width -= 3 * int(is_print_address)  # compensate ' in ' part
            value = part1 + part2 + '\n'
            value += ' ' * shift_width + ' at ' + part3
        else:
            value = parts

        return value

    def address(self):
        address = super(FrameColorizer, self).address()
        return '\033[1;30m0x%016x\033[0m' % address

    def depth(self):
        return '\033[1;37m#%-3d\033[0m' % self._depth

    def filename(self):
        filename = super(FrameColorizer, self).filename()
        return '\033[0;36m%s\033[0m' % filename

    def frame_args(self):
        try:
            block = self.frame.block()
        except RuntimeError:
            block = None

        while block is not None:
            if block.function is not None:
                break
            block = block.superblock

        if block is None:
            return ''

        args = []

        for sym in block:
            if not sym.is_argument:
                continue;
            val = sym.value(self.frame)
            arg = '%s=%s' % (sym, val) if str(val) else str(sym)
            args.append(arg)

        return ', '.join(args)

    def function(self):
        func = super(FrameColorizer, self).function()

        # GDB could somehow resolve function name by its address.
        # See details here https://cygwin.com/ml/gdb/2017-12/msg00013.html
        if isinstance(func, int):
            # Here we have something like
            # > raise + 272 in section .text of /usr/lib/libc.so.6
            # XXX: gdb.find_pc_line
            symbol = execute('info symbol 0x%016x' % func, False, True)

            # But here we truncate layout in binary
            # > raise + 272
            name = symbol[:symbol.find('in section')].strip()

            # Check if we in format
            # > smthing + offset
            parts = name.rsplit(' ', 1)
            # > raise
            if len(parts) == 1:
                return name

            try:
                offset = hex(int(parts[1]))
            except ValueError:
                return name

            return '\033[1;34m' + parts[0] + ' ' + offset + '\033[0m'
        else:
            return '\033[1;34m' + str(func) + '\033[0m'

    def get_screen_width(self):
        """Get screen width from GDB. Source format is following
        """
        return get_parameter('width')

    def line(self):
        value = super(FrameColorizer, self).line()
        return '\033[0;35m:%d\033[0m' % value if value else ''

    @staticmethod
    def length(colored_string):
        """This function calculates length of string with terminal control
        sequences.
        """
        start = 0
        term_seq_len = 0

        while True:
            begin = colored_string.find('\033', start)

            if begin == -1:
                break

            end = colored_string.find('m', begin)

            if end == -1:
                end = len(s)

            term_seq_len += end - begin + 1
            start = end

        return len(colored_string) - term_seq_len


class FilterProxy:
    """FilterProxy class keep ensures that frame iterator will be comsumed
    properly on the first and the sole call.
    """

    def __init__(self, frames):
        self.frames = (FrameColorizer(frame, ix)
                       for ix, frame in enumerate(frames))

    def __iter__(self):
        return self

    def next(self):
        self.unroll_stack()
        raise StopIteration

    def unroll_stack(self):
        output = (str(frame) for frame in self.frames)
        print('\n'.join(output))


class ColourFilter:

    def __init__(self, name='backtrace-filter', priority=0, enabled=True):
        """Frame filter with the lower priority that consumes every frame and
        colouring output.

        :param name: The name of the filter that GDB will display.
        :param priority: The priority of the filter relative to other filters.
        :param enabled: A boolean that indicates whether this filter is enabled
        and should be executed.
        """
        self.name = name
        self.priority = priority
        self.enabled = enabled

        # Register this frame filter with the global frame_filters
        # dictionary.
        frame_filters[self.name] = self

    def filter(self, iters):
        return FilterProxy(iters)


ColourFilter()  # register colour filter forcibly

[daskol]

@maksimovichsam Nice! However, I still recommend to switch to Python 3 or newer version of GDB with built-in colour support.