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171 lines
7.2 KiB
HTML
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<title>Exception Handling (Debugging with GDB)</title>
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Values-From-Inferior.html#Values-From-Inferior" rel="next" title="Values From Inferior">
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</head>
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<a name="Exception-Handling"></a>
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<div class="header">
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<p>
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Next: <a href="Values-From-Inferior.html#Values-From-Inferior" accesskey="n" rel="next">Values From Inferior</a>, Previous: <a href="Basic-Python.html#Basic-Python" accesskey="p" rel="prev">Basic Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Exception-Handling-1"></a>
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<h4 class="subsubsection">23.2.2.2 Exception Handling</h4>
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<a name="index-python-exceptions"></a>
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<a name="index-exceptions_002c-python"></a>
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<p>When executing the <code>python</code> command, Python exceptions
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uncaught within the Python code are translated to calls to
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<small>GDB</small> error-reporting mechanism. If the command that called
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<code>python</code> does not handle the error, <small>GDB</small> will
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terminate it and print an error message containing the Python
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exception name, the associated value, and the Python call stack
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backtrace at the point where the exception was raised. Example:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) python print foo
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Traceback (most recent call last):
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File "<string>", line 1, in <module>
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NameError: name 'foo' is not defined
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</pre></div>
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<p><small>GDB</small> errors that happen in <small>GDB</small> commands invoked by
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Python code are converted to Python exceptions. The type of the
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Python exception depends on the error.
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</p>
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<dl compact="compact">
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<dt><code>gdb.error</code>
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<a name="index-gdb_002eerror"></a>
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</dt>
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<dd><p>This is the base class for most exceptions generated by <small>GDB</small>.
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It is derived from <code>RuntimeError</code>, for compatibility with earlier
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versions of <small>GDB</small>.
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</p>
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<p>If an error occurring in <small>GDB</small> does not fit into some more
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specific category, then the generated exception will have this type.
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</p>
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</dd>
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<dt><code>gdb.MemoryError</code>
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<a name="index-gdb_002eMemoryError"></a>
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</dt>
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<dd><p>This is a subclass of <code>gdb.error</code> which is thrown when an
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operation tried to access invalid memory in the inferior.
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</p>
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</dd>
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<dt><code>KeyboardInterrupt</code>
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<a name="index-KeyboardInterrupt"></a>
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</dt>
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<dd><p>User interrupt (via <kbd>C-c</kbd> or by typing <kbd>q</kbd> at a pagination
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prompt) is translated to a Python <code>KeyboardInterrupt</code> exception.
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</p></dd>
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</dl>
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<p>In all cases, your exception handler will see the <small>GDB</small> error
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message as its value and the Python call stack backtrace at the Python
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statement closest to where the <small>GDB</small> error occured as the
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traceback.
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</p>
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<p>When implementing <small>GDB</small> commands in Python via
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<code>gdb.Command</code>, or functions via <code>gdb.Function</code>, it is useful
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to be able to throw an exception that doesn’t cause a traceback to be
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printed. For example, the user may have invoked the command
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incorrectly. <small>GDB</small> provides a special exception class that can
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be used for this purpose.
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</p>
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<dl compact="compact">
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<dt><code>gdb.GdbError</code>
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<a name="index-gdb_002eGdbError"></a>
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</dt>
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<dd><p>When thrown from a command or function, this exception will cause the
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command or function to fail, but the Python stack will not be
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displayed. <small>GDB</small> does not throw this exception itself, but
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rather recognizes it when thrown from user Python code. Example:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) python
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>class HelloWorld (gdb.Command):
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> """Greet the whole world."""
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> def __init__ (self):
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> super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
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> def invoke (self, args, from_tty):
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> argv = gdb.string_to_argv (args)
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> if len (argv) != 0:
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> raise gdb.GdbError ("hello-world takes no arguments")
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> print "Hello, World!"
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>HelloWorld ()
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>end
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(gdb) hello-world 42
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hello-world takes no arguments
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</pre></div>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Values-From-Inferior.html#Values-From-Inferior" accesskey="n" rel="next">Values From Inferior</a>, Previous: <a href="Basic-Python.html#Basic-Python" accesskey="p" rel="prev">Basic Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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