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<section id="debugging-c-api-extensions-and-cpython-internals-with-gdb">
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<span id="gdb"></span><h1>Debugging C API extensions and CPython Internals with GDB<a class="headerlink" href="#debugging-c-api-extensions-and-cpython-internals-with-gdb" title="Link to this heading">¶</a></h1>
|
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<p>This document explains how the Python GDB extension, <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code>, can
|
||
be used with the GDB debugger to debug CPython extensions and the
|
||
CPython interpreter itself.</p>
|
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<p>When debugging low-level problems such as crashes or deadlocks, a low-level
|
||
debugger, such as GDB, is useful to diagnose and correct the issue.
|
||
By default, GDB (or any of its front-ends) doesn’t support high-level
|
||
information specific to the CPython interpreter.</p>
|
||
<p>The <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code> extension adds CPython interpreter information to GDB.
|
||
The extension helps introspect the stack of currently executing Python functions.
|
||
Given a Python object represented by a <span class="c-expr sig sig-inline c"><a class="reference internal" href="../c-api/structures.html#c.PyObject" title="PyObject"><span class="n">PyObject</span></a><span class="p">*</span></span> pointer,
|
||
the extension surfaces the type and value of the object.</p>
|
||
<p>Developers who are working on CPython extensions or tinkering with parts
|
||
of CPython that are written in C can use this document to learn how to use the
|
||
<code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code> extension with GDB.</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">Note</p>
|
||
<p>This document assumes that you are familiar with the basics of GDB and the
|
||
CPython C API. It consolidates guidance from the
|
||
<a class="reference external" href="https://devguide.python.org">devguide</a> and the
|
||
<a class="reference external" href="https://wiki.python.org/moin/DebuggingWithGdb">Python wiki</a>.</p>
|
||
</div>
|
||
<section id="prerequisites">
|
||
<h2>Prerequisites<a class="headerlink" href="#prerequisites" title="Link to this heading">¶</a></h2>
|
||
<p>You need to have:</p>
|
||
<ul class="simple">
|
||
<li><p>GDB 7 or later. (For earlier versions of GDB, see <code class="docutils literal notranslate"><span class="pre">Misc/gdbinit</span></code> in the
|
||
sources of Python 3.11 or earlier.)</p></li>
|
||
<li><p>GDB-compatible debugging information for Python and any extension you are
|
||
debugging.</p></li>
|
||
<li><p>The <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code> extension.</p></li>
|
||
</ul>
|
||
<p>The extension is built with Python, but might be distributed separately or
|
||
not at all. Below, we include tips for a few common systems as examples.
|
||
Note that even if the instructions match your system, they might be outdated.</p>
|
||
<section id="setup-with-python-built-from-source">
|
||
<h3>Setup with Python built from source<a class="headerlink" href="#setup-with-python-built-from-source" title="Link to this heading">¶</a></h3>
|
||
<p>When you build CPython from source, debugging information should be available,
|
||
and the build should add a <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code> file to the root directory of
|
||
your repository.</p>
|
||
<p>To activate support, you must add the directory containing <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code>
|
||
to GDB’s “auto-load-safe-path”.
|
||
If you haven’t done this, recent versions of GDB will print out a warning
|
||
with instructions on how to do this.</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">Note</p>
|
||
<p>If you do not see instructions for your version of GDB, put this in your
|
||
configuration file (<code class="docutils literal notranslate"><span class="pre">~/.gdbinit</span></code> or <code class="docutils literal notranslate"><span class="pre">~/.config/gdb/gdbinit</span></code>):</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>add-auto-load-safe-path /path/to/cpython
|
||
</pre></div>
|
||
</div>
|
||
<p>You can also add multiple paths, separated by <code class="docutils literal notranslate"><span class="pre">:</span></code>.</p>
|
||
</div>
|
||
</section>
|
||
<section id="setup-for-python-from-a-linux-distro">
|
||
<h3>Setup for Python from a Linux distro<a class="headerlink" href="#setup-for-python-from-a-linux-distro" title="Link to this heading">¶</a></h3>
|
||
<p>Most Linux systems provide debug information for the system Python
|
||
in a package called <code class="docutils literal notranslate"><span class="pre">python-debuginfo</span></code>, <code class="docutils literal notranslate"><span class="pre">python-dbg</span></code> or similar.
|
||
For example:</p>
|
||
<ul>
|
||
<li><p>Fedora:</p>
|
||
<blockquote>
|
||
<div><div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>dnf<span class="w"> </span>install<span class="w"> </span>gdb
|
||
sudo<span class="w"> </span>dnf<span class="w"> </span>debuginfo-install<span class="w"> </span>python3
|
||
</pre></div>
|
||
</div>
|
||
</div></blockquote>
|
||
</li>
|
||
<li><p>Ubuntu:</p>
|
||
<blockquote>
|
||
<div><div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>apt<span class="w"> </span>install<span class="w"> </span>gdb<span class="w"> </span>python3-dbg
|
||
</pre></div>
|
||
</div>
|
||
</div></blockquote>
|
||
</li>
|
||
</ul>
|
||
<p>On several recent Linux systems, GDB can download debugging symbols
|
||
automatically using <em>debuginfod</em>.
|
||
However, this will not install the <code class="docutils literal notranslate"><span class="pre">python-gdb.py</span></code> extension;
|
||
you generally do need to install the debug info package separately.</p>
|
||
</section>
|
||
</section>
|
||
<section id="using-the-debug-build-and-development-mode">
|
||
<h2>Using the Debug build and Development mode<a class="headerlink" href="#using-the-debug-build-and-development-mode" title="Link to this heading">¶</a></h2>
|
||
<p>For easier debugging, you might want to:</p>
|
||
<ul class="simple">
|
||
<li><p>Use a <a class="reference internal" href="../using/configure.html#debug-build"><span class="std std-ref">debug build</span></a> of Python. (When building from source,
|
||
use <code class="docutils literal notranslate"><span class="pre">configure</span> <span class="pre">--with-pydebug</span></code>. On Linux distros, install and run a package
|
||
like <code class="docutils literal notranslate"><span class="pre">python-debug</span></code> or <code class="docutils literal notranslate"><span class="pre">python-dbg</span></code>, if available.)</p></li>
|
||
<li><p>Use the runtime <a class="reference internal" href="../library/devmode.html#devmode"><span class="std std-ref">development mode</span></a> (<code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">dev</span></code>).</p></li>
|
||
</ul>
|
||
<p>Both enable extra assertions and disable some optimizations.
|
||
Sometimes this hides the bug you are trying to find, but in most cases they
|
||
make the process easier.</p>
|
||
</section>
|
||
<section id="using-the-python-gdb-extension">
|
||
<h2>Using the <code class="docutils literal notranslate"><span class="pre">python-gdb</span></code> extension<a class="headerlink" href="#using-the-python-gdb-extension" title="Link to this heading">¶</a></h2>
|
||
<p>When the extension is loaded, it provides two main features:
|
||
pretty printers for Python values, and additional commands.</p>
|
||
<section id="pretty-printers">
|
||
<h3>Pretty-printers<a class="headerlink" href="#pretty-printers" title="Link to this heading">¶</a></h3>
|
||
<p>This is what a GDB backtrace looks like (truncated) when this extension is
|
||
enabled:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>#0 0x000000000041a6b1 in PyObject_Malloc (nbytes=Cannot access memory at address 0x7fffff7fefe8
|
||
) at Objects/obmalloc.c:748
|
||
#1 0x000000000041b7c0 in _PyObject_DebugMallocApi (id=111 'o', nbytes=24) at Objects/obmalloc.c:1445
|
||
#2 0x000000000041b717 in _PyObject_DebugMalloc (nbytes=24) at Objects/obmalloc.c:1412
|
||
#3 0x000000000044060a in _PyUnicode_New (length=11) at Objects/unicodeobject.c:346
|
||
#4 0x00000000004466aa in PyUnicodeUCS2_DecodeUTF8Stateful (s=0x5c2b8d "__lltrace__", size=11, errors=0x0, consumed=
|
||
0x0) at Objects/unicodeobject.c:2531
|
||
#5 0x0000000000446647 in PyUnicodeUCS2_DecodeUTF8 (s=0x5c2b8d "__lltrace__", size=11, errors=0x0)
|
||
at Objects/unicodeobject.c:2495
|
||
#6 0x0000000000440d1b in PyUnicodeUCS2_FromStringAndSize (u=0x5c2b8d "__lltrace__", size=11)
|
||
at Objects/unicodeobject.c:551
|
||
#7 0x0000000000440d94 in PyUnicodeUCS2_FromString (u=0x5c2b8d "__lltrace__") at Objects/unicodeobject.c:569
|
||
#8 0x0000000000584abd in PyDict_GetItemString (v=
|
||
{'Yuck': <type at remote 0xad4730>, '__builtins__': <module at remote 0x7ffff7fd5ee8>, '__file__': 'Lib/test/crashers/nasty_eq_vs_dict.py', '__package__': None, 'y': <Yuck(i=0) at remote 0xaacd80>, 'dict': {0: 0, 1: 1, 2: 2, 3: 3}, '__cached__': None, '__name__': '__main__', 'z': <Yuck(i=0) at remote 0xaace60>, '__doc__': None}, key=
|
||
0x5c2b8d "__lltrace__") at Objects/dictobject.c:2171
|
||
</pre></div>
|
||
</div>
|
||
<p>Notice how the dictionary argument to <code class="docutils literal notranslate"><span class="pre">PyDict_GetItemString</span></code> is displayed
|
||
as its <code class="docutils literal notranslate"><span class="pre">repr()</span></code>, rather than an opaque <code class="docutils literal notranslate"><span class="pre">PyObject</span> <span class="pre">*</span></code> pointer.</p>
|
||
<p>The extension works by supplying a custom printing routine for values of type
|
||
<code class="docutils literal notranslate"><span class="pre">PyObject</span> <span class="pre">*</span></code>. If you need to access lower-level details of an object, then
|
||
cast the value to a pointer of the appropriate type. For example:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p globals
|
||
$1 = {'__builtins__': <module at remote 0x7ffff7fb1868>, '__name__':
|
||
'__main__', 'ctypes': <module at remote 0x7ffff7f14360>, '__doc__': None,
|
||
'__package__': None}
|
||
|
||
(gdb) p *(PyDictObject*)globals
|
||
$2 = {ob_refcnt = 3, ob_type = 0x3dbdf85820, ma_fill = 5, ma_used = 5,
|
||
ma_mask = 7, ma_table = 0x63d0f8, ma_lookup = 0x3dbdc7ea70
|
||
<lookdict_string>, ma_smalltable = {{me_hash = 7065186196740147912,
|
||
me_key = '__builtins__', me_value = <module at remote 0x7ffff7fb1868>},
|
||
{me_hash = -368181376027291943, me_key = '__name__',
|
||
me_value ='__main__'}, {me_hash = 0, me_key = 0x0, me_value = 0x0},
|
||
{me_hash = 0, me_key = 0x0, me_value = 0x0},
|
||
{me_hash = -9177857982131165996, me_key = 'ctypes',
|
||
me_value = <module at remote 0x7ffff7f14360>},
|
||
{me_hash = -8518757509529533123, me_key = '__doc__', me_value = None},
|
||
{me_hash = 0, me_key = 0x0, me_value = 0x0}, {
|
||
me_hash = 6614918939584953775, me_key = '__package__', me_value = None}}}
|
||
</pre></div>
|
||
</div>
|
||
<p>Note that the pretty-printers do not actually call <code class="docutils literal notranslate"><span class="pre">repr()</span></code>.
|
||
For basic types, they try to match its result closely.</p>
|
||
<p>An area that can be confusing is that the custom printer for some types look a
|
||
lot like GDB’s built-in printer for standard types. For example, the
|
||
pretty-printer for a Python <code class="docutils literal notranslate"><span class="pre">int</span></code> (<span class="c-expr sig sig-inline c"><a class="reference internal" href="../c-api/long.html#c.PyLongObject" title="PyLongObject"><span class="n">PyLongObject</span></a><span class="p">*</span></span>)
|
||
gives a representation that is not distinguishable from one of a
|
||
regular machine-level integer:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p some_machine_integer
|
||
$3 = 42
|
||
|
||
(gdb) p some_python_integer
|
||
$4 = 42
|
||
</pre></div>
|
||
</div>
|
||
<p>The internal structure can be revealed with a cast to <span class="c-expr sig sig-inline c"><a class="reference internal" href="../c-api/long.html#c.PyLongObject" title="PyLongObject"><span class="n">PyLongObject</span></a><span class="p">*</span></span>:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p *(PyLongObject*)some_python_integer
|
||
$5 = {ob_base = {ob_base = {ob_refcnt = 8, ob_type = 0x3dad39f5e0}, ob_size = 1},
|
||
ob_digit = {42}}
|
||
</pre></div>
|
||
</div>
|
||
<p>A similar confusion can arise with the <code class="docutils literal notranslate"><span class="pre">str</span></code> type, where the output looks a
|
||
lot like gdb’s built-in printer for <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code>:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p ptr_to_python_str
|
||
$6 = '__builtins__'
|
||
</pre></div>
|
||
</div>
|
||
<p>The pretty-printer for <code class="docutils literal notranslate"><span class="pre">str</span></code> instances defaults to using single-quotes (as
|
||
does Python’s <code class="docutils literal notranslate"><span class="pre">repr</span></code> for strings) whereas the standard printer for <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code>
|
||
values uses double-quotes and contains a hexadecimal address:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p ptr_to_char_star
|
||
$7 = 0x6d72c0 "hello world"
|
||
</pre></div>
|
||
</div>
|
||
<p>Again, the implementation details can be revealed with a cast to
|
||
<span class="c-expr sig sig-inline c"><a class="reference internal" href="../c-api/unicode.html#c.PyUnicodeObject" title="PyUnicodeObject"><span class="n">PyUnicodeObject</span></a><span class="p">*</span></span>:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) p *(PyUnicodeObject*)$6
|
||
$8 = {ob_base = {ob_refcnt = 33, ob_type = 0x3dad3a95a0}, length = 12,
|
||
str = 0x7ffff2128500, hash = 7065186196740147912, state = 1, defenc = 0x0}
|
||
</pre></div>
|
||
</div>
|
||
</section>
|
||
<section id="py-list">
|
||
<h3><code class="docutils literal notranslate"><span class="pre">py-list</span></code><a class="headerlink" href="#py-list" title="Link to this heading">¶</a></h3>
|
||
<blockquote>
|
||
<div><p>The extension adds a <code class="docutils literal notranslate"><span class="pre">py-list</span></code> command, which
|
||
lists the Python source code (if any) for the current frame in the selected
|
||
thread. The current line is marked with a “>”:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-list
|
||
901 if options.profile:
|
||
902 options.profile = False
|
||
903 profile_me()
|
||
904 return
|
||
905
|
||
>906 u = UI()
|
||
907 if not u.quit:
|
||
908 try:
|
||
909 gtk.main()
|
||
910 except KeyboardInterrupt:
|
||
911 # properly quit on a keyboard interrupt...
|
||
</pre></div>
|
||
</div>
|
||
<p>Use <code class="docutils literal notranslate"><span class="pre">py-list</span> <span class="pre">START</span></code> to list at a different line number within the Python
|
||
source, and <code class="docutils literal notranslate"><span class="pre">py-list</span> <span class="pre">START,END</span></code> to list a specific range of lines within
|
||
the Python source.</p>
|
||
</div></blockquote>
|
||
</section>
|
||
<section id="py-up-and-py-down">
|
||
<h3><code class="docutils literal notranslate"><span class="pre">py-up</span></code> and <code class="docutils literal notranslate"><span class="pre">py-down</span></code><a class="headerlink" href="#py-up-and-py-down" title="Link to this heading">¶</a></h3>
|
||
<blockquote>
|
||
<div><p>The <code class="docutils literal notranslate"><span class="pre">py-up</span></code> and <code class="docutils literal notranslate"><span class="pre">py-down</span></code> commands are analogous to GDB’s regular <code class="docutils literal notranslate"><span class="pre">up</span></code>
|
||
and <code class="docutils literal notranslate"><span class="pre">down</span></code> commands, but try to move at the level of CPython frames, rather
|
||
than C frames.</p>
|
||
<p>GDB is not always able to read the relevant frame information, depending on
|
||
the optimization level with which CPython was compiled. Internally, the
|
||
commands look for C frames that are executing the default frame evaluation
|
||
function (that is, the core bytecode interpreter loop within CPython) and
|
||
look up the value of the related <code class="docutils literal notranslate"><span class="pre">PyFrameObject</span> <span class="pre">*</span></code>.</p>
|
||
<p>They emit the frame number (at the C level) within the thread.</p>
|
||
<p>For example:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-up
|
||
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/
|
||
gnome_sudoku/main.py, line 906, in start_game ()
|
||
u = UI()
|
||
(gdb) py-up
|
||
#40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/
|
||
gnome_sudoku/gnome_sudoku.py, line 22, in start_game(main=<module at remote 0xb771b7f4>)
|
||
main.start_game()
|
||
(gdb) py-up
|
||
Unable to find an older python frame
|
||
</pre></div>
|
||
</div>
|
||
<p>so we’re at the top of the Python stack.</p>
|
||
<p>The frame numbers correspond to those displayed by GDB’s standard
|
||
<code class="docutils literal notranslate"><span class="pre">backtrace</span></code> command.
|
||
The command skips C frames which are not executing Python code.</p>
|
||
<p>Going back down:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-down
|
||
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
|
||
u = UI()
|
||
(gdb) py-down
|
||
#34 (unable to read python frame information)
|
||
(gdb) py-down
|
||
#23 (unable to read python frame information)
|
||
(gdb) py-down
|
||
#19 (unable to read python frame information)
|
||
(gdb) py-down
|
||
#14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
|
||
swallower.run_dialog(self.dialog)
|
||
(gdb) py-down
|
||
#11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
|
||
gtk.main()
|
||
(gdb) py-down
|
||
#8 (unable to read python frame information)
|
||
(gdb) py-down
|
||
Unable to find a newer python frame
|
||
</pre></div>
|
||
</div>
|
||
<p>and we’re at the bottom of the Python stack.</p>
|
||
<p>Note that in Python 3.12 and newer, the same C stack frame can be used for
|
||
multiple Python stack frames. This means that <code class="docutils literal notranslate"><span class="pre">py-up</span></code> and <code class="docutils literal notranslate"><span class="pre">py-down</span></code>
|
||
may move multiple Python frames at once. For example:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-up
|
||
#6 Frame 0x7ffff7fb62b0, for file /tmp/rec.py, line 5, in recursive_function (n=0)
|
||
time.sleep(5)
|
||
#6 Frame 0x7ffff7fb6240, for file /tmp/rec.py, line 7, in recursive_function (n=1)
|
||
recursive_function(n-1)
|
||
#6 Frame 0x7ffff7fb61d0, for file /tmp/rec.py, line 7, in recursive_function (n=2)
|
||
recursive_function(n-1)
|
||
#6 Frame 0x7ffff7fb6160, for file /tmp/rec.py, line 7, in recursive_function (n=3)
|
||
recursive_function(n-1)
|
||
#6 Frame 0x7ffff7fb60f0, for file /tmp/rec.py, line 7, in recursive_function (n=4)
|
||
recursive_function(n-1)
|
||
#6 Frame 0x7ffff7fb6080, for file /tmp/rec.py, line 7, in recursive_function (n=5)
|
||
recursive_function(n-1)
|
||
#6 Frame 0x7ffff7fb6020, for file /tmp/rec.py, line 9, in <module> ()
|
||
recursive_function(5)
|
||
(gdb) py-up
|
||
Unable to find an older python frame
|
||
</pre></div>
|
||
</div>
|
||
</div></blockquote>
|
||
</section>
|
||
<section id="py-bt">
|
||
<h3><code class="docutils literal notranslate"><span class="pre">py-bt</span></code><a class="headerlink" href="#py-bt" title="Link to this heading">¶</a></h3>
|
||
<blockquote>
|
||
<div><p>The <code class="docutils literal notranslate"><span class="pre">py-bt</span></code> command attempts to display a Python-level backtrace of the
|
||
current thread.</p>
|
||
<p>For example:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-bt
|
||
#8 (unable to read python frame information)
|
||
#11 Frame 0x9aead74, for file /usr/lib/python2.6/site-packages/gnome_sudoku/dialog_swallower.py, line 48, in run_dialog (self=<SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>, main_page=0) at remote 0x98fa6e4>, d=<gtk.Dialog at remote 0x98faaa4>)
|
||
gtk.main()
|
||
#14 Frame 0x99262ac, for file /usr/lib/python2.6/site-packages/gnome_sudoku/game_selector.py, line 201, in run_swallowed_dialog (self=<NewOrSavedGameSelector(new_game_model=<gtk.ListStore at remote 0x98fab44>, puzzle=None, saved_games=[{'gsd.auto_fills': 0, 'tracking': {}, 'trackers': {}, 'notes': [], 'saved_at': 1270084485, 'game': '7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5\n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5', 'gsd.impossible_hints': 0, 'timer.__absolute_start_time__': <float at remote 0x984b474>, 'gsd.hints': 0, 'timer.active_time': <float at remote 0x984b494>, 'timer.total_time': <float at remote 0x984b464>}], dialog=<gtk.Dialog at remote 0x98faaa4>, saved_game_model=<gtk.ListStore at remote 0x98fad24>, sudoku_maker=<SudokuMaker(terminated=False, played=[], batch_siz...(truncated)
|
||
swallower.run_dialog(self.dialog)
|
||
#19 (unable to read python frame information)
|
||
#23 (unable to read python frame information)
|
||
#34 (unable to read python frame information)
|
||
#37 Frame 0x9420b04, for file /usr/lib/python2.6/site-packages/gnome_sudoku/main.py, line 906, in start_game ()
|
||
u = UI()
|
||
#40 Frame 0x948e82c, for file /usr/lib/python2.6/site-packages/gnome_sudoku/gnome_sudoku.py, line 22, in start_game (main=<module at remote 0xb771b7f4>)
|
||
main.start_game()
|
||
</pre></div>
|
||
</div>
|
||
<p>The frame numbers correspond to those displayed by GDB’s standard
|
||
<code class="docutils literal notranslate"><span class="pre">backtrace</span></code> command.</p>
|
||
</div></blockquote>
|
||
</section>
|
||
<section id="py-print">
|
||
<h3><code class="docutils literal notranslate"><span class="pre">py-print</span></code><a class="headerlink" href="#py-print" title="Link to this heading">¶</a></h3>
|
||
<blockquote>
|
||
<div><p>The <code class="docutils literal notranslate"><span class="pre">py-print</span></code> command looks up a Python name and tries to print it.
|
||
It looks in locals within the current thread, then globals, then finally
|
||
builtins:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-print self
|
||
local 'self' = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
|
||
main_page=0) at remote 0x98fa6e4>
|
||
(gdb) py-print __name__
|
||
global '__name__' = 'gnome_sudoku.dialog_swallower'
|
||
(gdb) py-print len
|
||
builtin 'len' = <built-in function len>
|
||
(gdb) py-print scarlet_pimpernel
|
||
'scarlet_pimpernel' not found
|
||
</pre></div>
|
||
</div>
|
||
<p>If the current C frame corresponds to multiple Python frames, <code class="docutils literal notranslate"><span class="pre">py-print</span></code>
|
||
only considers the first one.</p>
|
||
</div></blockquote>
|
||
</section>
|
||
<section id="py-locals">
|
||
<h3><code class="docutils literal notranslate"><span class="pre">py-locals</span></code><a class="headerlink" href="#py-locals" title="Link to this heading">¶</a></h3>
|
||
<blockquote>
|
||
<div><p>The <code class="docutils literal notranslate"><span class="pre">py-locals</span></code> command looks up all Python locals within the current
|
||
Python frame in the selected thread, and prints their representations:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-locals
|
||
self = <SwappableArea(running=<gtk.Dialog at remote 0x98faaa4>,
|
||
main_page=0) at remote 0x98fa6e4>
|
||
d = <gtk.Dialog at remote 0x98faaa4>
|
||
</pre></div>
|
||
</div>
|
||
<p>If the current C frame corresponds to multiple Python frames, locals from
|
||
all of them will be shown:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-locals
|
||
Locals for recursive_function
|
||
n = 0
|
||
Locals for recursive_function
|
||
n = 1
|
||
Locals for recursive_function
|
||
n = 2
|
||
Locals for recursive_function
|
||
n = 3
|
||
Locals for recursive_function
|
||
n = 4
|
||
Locals for recursive_function
|
||
n = 5
|
||
Locals for <module>
|
||
</pre></div>
|
||
</div>
|
||
</div></blockquote>
|
||
</section>
|
||
</section>
|
||
<section id="use-with-gdb-commands">
|
||
<h2>Use with GDB commands<a class="headerlink" href="#use-with-gdb-commands" title="Link to this heading">¶</a></h2>
|
||
<p>The extension commands complement GDB’s built-in commands.
|
||
For example, you can use a frame numbers shown by <code class="docutils literal notranslate"><span class="pre">py-bt</span></code> with the <code class="docutils literal notranslate"><span class="pre">frame</span></code>
|
||
command to go a specific frame within the selected thread, like this:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) py-bt
|
||
(output snipped)
|
||
#68 Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> ()
|
||
main()
|
||
(gdb) frame 68
|
||
#68 0x00000000004cd1e6 in PyEval_EvalFrameEx (f=Frame 0xaa4560, for file Lib/test/regrtest.py, line 1548, in <module> (), throwflag=0) at Python/ceval.c:2665
|
||
2665 x = call_function(&sp, oparg);
|
||
(gdb) py-list
|
||
1543 # Run the tests in a context manager that temporary changes the CWD to a
|
||
1544 # temporary and writable directory. If it's not possible to create or
|
||
1545 # change the CWD, the original CWD will be used. The original CWD is
|
||
1546 # available from test_support.SAVEDCWD.
|
||
1547 with test_support.temp_cwd(TESTCWD, quiet=True):
|
||
>1548 main()
|
||
</pre></div>
|
||
</div>
|
||
<p>The <code class="docutils literal notranslate"><span class="pre">info</span> <span class="pre">threads</span></code> command will give you a list of the threads within the
|
||
process, and you can use the <code class="docutils literal notranslate"><span class="pre">thread</span></code> command to select a different one:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) info threads
|
||
105 Thread 0x7fffefa18710 (LWP 10260) sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
|
||
104 Thread 0x7fffdf5fe710 (LWP 10259) sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
|
||
* 1 Thread 0x7ffff7fe2700 (LWP 10145) 0x00000038e46d73e3 in select () at ../sysdeps/unix/syscall-template.S:82
|
||
</pre></div>
|
||
</div>
|
||
<p>You can use <code class="docutils literal notranslate"><span class="pre">thread</span> <span class="pre">apply</span> <span class="pre">all</span> <span class="pre">COMMAND</span></code> or (<code class="docutils literal notranslate"><span class="pre">t</span> <span class="pre">a</span> <span class="pre">a</span> <span class="pre">COMMAND</span></code> for short) to run
|
||
a command on all threads. With <code class="docutils literal notranslate"><span class="pre">py-bt</span></code>, this lets you see what every
|
||
thread is doing at the Python level:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) t a a py-bt
|
||
|
||
Thread 105 (Thread 0x7fffefa18710 (LWP 10260)):
|
||
#5 Frame 0x7fffd00019d0, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140737213728528), count=1, owner=140737213728528)
|
||
self.__block.acquire()
|
||
#8 Frame 0x7fffac001640, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858a90>, saved_state=(1, 140737213728528))
|
||
self._acquire_restore(saved_state)
|
||
#12 Frame 0x7fffb8001a10, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
|
||
cond.wait()
|
||
#16 Frame 0x7fffb8001c40, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140737213728528)
|
||
f()
|
||
|
||
Thread 104 (Thread 0x7fffdf5fe710 (LWP 10259)):
|
||
#5 Frame 0x7fffe4001580, for file /home/david/coding/python-svn/Lib/threading.py, line 155, in _acquire_restore (self=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, count_owner=(1, 140736940992272), count=1, owner=140736940992272)
|
||
self.__block.acquire()
|
||
#8 Frame 0x7fffc8002090, for file /home/david/coding/python-svn/Lib/threading.py, line 269, in wait (self=<_Condition(_Condition__lock=<_RLock(_Verbose__verbose=False, _RLock__owner=140737354016512, _RLock__block=<thread.lock at remote 0x858770>, _RLock__count=1) at remote 0xd7ff40>, acquire=<instancemethod at remote 0xd80260>, _is_owned=<instancemethod at remote 0xd80160>, _release_save=<instancemethod at remote 0xd803e0>, release=<instancemethod at remote 0xd802e0>, _acquire_restore=<instancemethod at remote 0xd7ee60>, _Verbose__verbose=False, _Condition__waiters=[]) at remote 0xd7fd10>, timeout=None, waiter=<thread.lock at remote 0x858860>, saved_state=(1, 140736940992272))
|
||
self._acquire_restore(saved_state)
|
||
#12 Frame 0x7fffac001c90, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 348, in f ()
|
||
cond.wait()
|
||
#16 Frame 0x7fffac0011c0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 37, in task (tid=140736940992272)
|
||
f()
|
||
|
||
Thread 1 (Thread 0x7ffff7fe2700 (LWP 10145)):
|
||
#5 Frame 0xcb5380, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 16, in _wait ()
|
||
time.sleep(0.01)
|
||
#8 Frame 0x7fffd00024a0, for file /home/david/coding/python-svn/Lib/test/lock_tests.py, line 378, in _check_notify (self=<ConditionTests(_testMethodName='test_notify', _resultForDoCleanups=<TestResult(_original_stdout=<cStringIO.StringO at remote 0xc191e0>, skipped=[], _mirrorOutput=False, testsRun=39, buffer=False, _original_stderr=<file at remote 0x7ffff7fc6340>, _stdout_buffer=<cStringIO.StringO at remote 0xc9c7f8>, _stderr_buffer=<cStringIO.StringO at remote 0xc9c790>, _moduleSetUpFailed=False, expectedFailures=[], errors=[], _previousTestClass=<type at remote 0x928310>, unexpectedSuccesses=[], failures=[], shouldStop=False, failfast=False) at remote 0xc185a0>, _threads=(0,), _cleanups=[], _type_equality_funcs={<type at remote 0x7eba00>: <instancemethod at remote 0xd750e0>, <type at remote 0x7e7820>: <instancemethod at remote 0xd75160>, <type at remote 0x7e30e0>: <instancemethod at remote 0xd75060>, <type at remote 0x7e7d20>: <instancemethod at remote 0xd751e0>, <type at remote 0x7f19e0...(truncated)
|
||
_wait()
|
||
</pre></div>
|
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<li><a class="reference internal" href="#using-the-debug-build-and-development-mode">Using the Debug build and Development mode</a></li>
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|
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<li><a class="reference internal" href="#py-bt"><code class="docutils literal notranslate"><span class="pre">py-bt</span></code></a></li>
|
||
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|
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|
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|
||
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|
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|
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