如何调试free（）：Python/Kivy中的无效nex大小错误？

Question

在Kivy，我有时会遇到以下错误：

*** Error in `python': free(): invalid next size (fast): 0x0000000001d67800 ***
Aborted (core dumped)

不是每次我测试程序都会发生这种情况，这让我很困惑。在

在搜索错误消息时，我认为它与C代码有关。 我想我正在用python做一些事情，导致kivyc代码中的这个bug。在

我想知道怎样才能追踪到这样的虫子。在

版本：

• Python版本：2.7.5-5ubuntu3

• Cython版本：0.20.1+git90-g0e6e38e-1ubuntu2

• Kivy版本：1.8.0-stable0+201401301617^pkg23^ubuntu13.10。

Answer 1

首先，安装gdb和Python调试：sudo apt-get install gdb python2.7-dbg

然后在gdb中加载你的应用程序：gdb args python <script.py>

您应该会收到一个gdb提示(gdb)。键入r，然后按Enter键。您的程序将开始正常运行（尽管速度较慢）。在

一旦应用程序崩溃，Kivy窗口将保持打开状态，gdbshell将再次显示提示。在这个提示下输入bt以查看回溯。在

示例：

$ gdb  args python segtest.py
GNU gdb (GDB) 7.6.1-ubuntu
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/python2.7...Reading symbols from /usr/lib/debug/usr/bin/python2.7...done.
done.
(gdb) r
Starting program: /usr/bin/python segtest.py
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7ffff7ffa000
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[INFO   ] [Logger      ] Record log in /home/ryan/.kivy/logs/kivy_14-07-28_13.txt
[INFO   ] [Factory     ] 169 symbols loaded
[DEBUG  ] [Cache       ] register <kv.image> with limit=None, timeout=60s
[DEBUG  ] [Cache       ] register <kv.atlas> with limit=None, timeout=Nones
[INFO   ] [Image       ] Providers: img_tex, img_dds, img_pygame, img_pil, img_gif 
[DEBUG  ] [Cache       ] register <kv.texture> with limit=1000, timeout=60s
[DEBUG  ] [Cache       ] register <kv.shader> with limit=1000, timeout=3600s
[DEBUG  ] [Cache       ] register <kv.lang> with limit=None, timeout=Nones
[INFO   ] [Text        ] Provider: pygame
[DEBUG  ] [Cache       ] register <textinput.label> with limit=None, timeout=60.0s
[DEBUG  ] [Cache       ] register <textinput.width> with limit=None, timeout=60.0s
[INFO   ] Kivy v1.8.1-dev
[INFO   ] [Python      ] v2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2]
[DEBUG  ] [Window      ] Ignored <egl_rpi> (import error)
[INFO   ] [Window      ] Provider: pygame(['window_egl_rpi'] ignored)
[DEBUG  ] [Window      ] Display driver x11
[DEBUG  ] [Window      ] Actual window size: 800x600
[DEBUG  ] [Window      ] Actual color bits r8 g8 b8 a8
[DEBUG  ] [Window      ] Actual depth bits: 24
[DEBUG  ] [Window      ] Actual stencil bits: 8
[DEBUG  ] [Window      ] Actual multisampling samples: 4
[INFO   ] [GL          ] OpenGL version <3.0 Mesa 10.1.3>
[INFO   ] [GL          ] OpenGL vendor <Intel Open Source Technology Center>
[INFO   ] [GL          ] OpenGL renderer <Mesa DRI Intel(R) Sandybridge Mobile >
[INFO   ] [GL          ] OpenGL parsed version: 3, 0
[INFO   ] [GL          ] Shading version <1.30>
[INFO   ] [GL          ] Texture max size <8192>
[INFO   ] [GL          ] Texture max units <16>
[DEBUG  ] [Shader      ] Fragment compiled successfully
[DEBUG  ] [Shader      ] Vertex compiled successfully
[DEBUG  ] [ImagePygame ] Load </home/ryan/git/aeris2/kivy/kivy/data/glsl/default.png>
[DEBUG  ] [Modules     ] Start <inspector> with config {}
[INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked
[DEBUG  ] [App         ] Loading kv <./test.kv>

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff5971db6 in __pyx_f_4kivy_8graphics_12instructions_6Canvas_add (__pyx_v_self=0x7fffe2ec4a68, 
    __pyx_v_c=0x920190 <_Py_NoneStruct>, __pyx_skip_dispatch=<optimized out>) at kivy/graphics/instructions.c:8532
8532        ((struct __pyx_vtabstruct_4kivy_8graphics_12instructions_Instruction *)__pyx_v_c->__pyx_vtab)->radd(__pyx_v_c, ((struct __pyx_obj_4kivy_8graphics_12instructions_InstructionGroup *)__pyx_v_self));
(gdb) bt
#0  0x00007ffff5971db6 in __pyx_f_4kivy_8graphics_12instructions_6Canvas_add (__pyx_v_self=0x7fffe2ec4a68, 
    __pyx_v_c=0x920190 <_Py_NoneStruct>, __pyx_skip_dispatch=<optimized out>) at kivy/graphics/instructions.c:8532
#1  0x00007ffff597487e in __pyx_pf_4kivy_8graphics_12instructions_6Canvas_6add (
    __pyx_v_c=0x920190 <_Py_NoneStruct>, __pyx_v_self=0x7fffe2ec4a68) at kivy/graphics/instructions.c:8611
#2  __pyx_pw_4kivy_8graphics_12instructions_6Canvas_7add (
    __pyx_v_self=<kivy.graphics.instructions.Canvas at remote 0x7fffe2ec4a68>, __pyx_v_c=None)
    at kivy/graphics/instructions.c:8591
#3  0x000000000052ccbc in call_function (oparg=<optimized out>, pp_stack=0x7fffffffd870) at ../Python/ceval.c:4008
#4  PyEval_EvalFrameEx (
    f=f@entry=Frame 0x7fffdfa10050, for file /home/ryan/git/aeris2/kivy/kivy/core/window/__init__.py, line 647, in add_widget (self=<WindowPygame(_context=<Context(sandbox=None) at remote 0x7ffff659a740>, single_vkeyboard=True, _keyboards={'system': <Keyboard(widget=None, callback=None, window=<...>, target=None) at remote 0x7fffe2ebf0b8>}, _vkeyboard_cls=None, _system_keyboard=<...>, _pos=(0, 0), allow_vkeyboard=False, use_syskeyboard=True, flags=1073741843, trigger_keyboard_height=<ClockEvent(_last_dt=0, cid=207, clock=<ClockBase at remote 0x7ffff65c4a28>, weak_callback=<WeakMethod(_func=<function at remote 0x7fffe2e9fed8>, _obj=<weakref at remote 0x7fffe2ec2050>, _class=<type at remote 0x1029ac0>) at remote 0x7fffe2ebc9d0>, callback=None, timeout=<float at remote 0xf0ea98>, _is_triggered=False, _dt=<float at remote 0xa83608>, loop=False) at remote 0x7fffe2ebc990>, initialized=True, docked_vkeyboard=False, dpi=<float at remote 0xf0e930>, trigger_create_window=<ClockEvent(_last_dt=0, cid=207, clock=<...>, weak_callback=<W...(truncated), throwflag=throwflag@entry=0) at ../Python/ceval.c:2666
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