121 lines
5.7 KiB
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121 lines
5.7 KiB
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<title>Exception Handling - Debugging with GDB</title>
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<div class="node">
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<a name="Exception-Handling"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Values-From-Inferior.html#Values-From-Inferior">Values From Inferior</a>,
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Previous: <a rel="previous" accesskey="p" href="Basic-Python.html#Basic-Python">Basic Python</a>,
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Up: <a rel="up" accesskey="u" href="Python-API.html#Python-API">Python API</a>
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<hr>
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</div>
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<h5 class="subsubsection">23.2.2.2 Exception Handling</h5>
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<p><a name="index-python-exceptions-1899"></a><a name="index-exceptions_002c-python-1900"></a>
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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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<span class="sc">gdb</span> error-reporting mechanism. If the command that called
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<code>python</code> does not handle the error, <span class="sc">gdb</span> 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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<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>
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<p><span class="sc">gdb</span> errors that happen in <span class="sc">gdb</span> 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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<dl>
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<dt><code>gdb.error</code><a name="index-gdb_002eerror-1901"></a><dd>This is the base class for most exceptions generated by <span class="sc">gdb</span>.
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It is derived from <code>RuntimeError</code>, for compatibility with earlier
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versions of <span class="sc">gdb</span>.
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<p>If an error occurring in <span class="sc">gdb</span> does not fit into some more
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specific category, then the generated exception will have this type.
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<br><dt><code>gdb.MemoryError</code><a name="index-gdb_002eMemoryError-1902"></a><dd>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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<br><dt><code>KeyboardInterrupt</code><a name="index-KeyboardInterrupt-1903"></a><dd>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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</dl>
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<p>In all cases, your exception handler will see the <span class="sc">gdb</span> 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 <span class="sc">gdb</span> error occured as the
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traceback.
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<p>When implementing <span class="sc">gdb</span> 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. <span class="sc">gdb</span> provides a special exception class that can
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be used for this purpose.
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<dl>
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<dt><code>gdb.GdbError</code><a name="index-gdb_002eGdbError-1904"></a><dd>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. <span class="sc">gdb</span> 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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<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>
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</dl>
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</body></html>
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