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Initial commit of OpenSPARC T2 design and verification files.
[OpenSPARC-T2-DV] / tools / src / nas,5.n2.os.2 / lib / python / html / python / lib / debugger-hooks.html
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53
54<H1><A NAME="SECTION0011200000000000000000"></A><A NAME="debugger-hooks"></A>
55<BR>
569.2 How It Works
57</H1>
58
59<P>
60Some changes were made to the interpreter:
61
62<P>
63
64<UL>
65<LI><code>sys.settrace(<var>func</var>)</code> sets the global trace function
66</LI>
67<LI>there can also a local trace function (see later)
68</LI>
69</UL>
70
71<P>
72Trace functions have three arguments: <var>frame</var>, <var>event</var>, and
73<var>arg</var>. <var>frame</var> is the current stack frame. <var>event</var> is a
74string: <code>'call'</code>, <code>'line'</code>, <code>'return'</code>, <code>'exception'</code>,
75 <code>'c_call'</code>, <code>'c_return'</code>, or <code>'c_exception'</code>. <var>arg</var>
76 depends on the event type.
77
78<P>
79The global trace function is invoked (with <var>event</var> set to
80<code>'call'</code>) whenever a new local scope is entered; it should return
81a reference to the local trace function to be used that scope, or
82<code>None</code> if the scope shouldn't be traced.
83
84<P>
85The local trace function should return a reference to itself (or to
86another function for further tracing in that scope), or <code>None</code> to
87turn off tracing in that scope.
88
89<P>
90Instance methods are accepted (and very useful!) as trace functions.
91
92<P>
93The events have the following meaning:
94
95<P>
96<DL>
97<DT><STRONG><code>'call'</code></STRONG></DT>
98<DD>A function is called (or some other code block entered). The global
99trace function is called; <var>arg</var> is <code>None</code>;
100the return value specifies the local trace function.
101
102<P>
103</DD>
104<DT><STRONG><code>'line'</code></STRONG></DT>
105<DD>The interpreter is about to execute a new line of code (sometimes
106multiple line events on one line exist). The local trace function is
107called; <var>arg</var> is <code>None</code>; the return value specifies the new
108local trace function.
109
110<P>
111</DD>
112<DT><STRONG><code>'return'</code></STRONG></DT>
113<DD>A function (or other code block) is about to return. The local trace
114function is called; <var>arg</var> is the value that will be returned. The
115trace function's return value is ignored.
116
117<P>
118</DD>
119<DT><STRONG><code>'exception'</code></STRONG></DT>
120<DD>An exception has occurred. The local trace function is called;
121<var>arg</var> is a triple <code>(<var>exception</var>, <var>value</var>,
122<var>traceback</var>)</code>; the return value specifies the new local trace
123function.
124
125<P>
126</DD>
127<DT><STRONG><code>'c_call'</code></STRONG></DT>
128<DD>A C function is about to be called. This may be an extension function
129or a builtin. <var>arg</var> is the C function object.
130
131<P>
132</DD>
133<DT><STRONG><code>'c_return'</code></STRONG></DT>
134<DD>A C function has returned. <var>arg</var> is <code>None</code>.
135
136<P>
137</DD>
138<DT><STRONG><code>'c_exception'</code></STRONG></DT>
139<DD>A C function has thrown an exception. <var>arg</var> is <code>None</code>.
140
141<P>
142</DD>
143</DL>
144
145<P>
146Note that as an exception is propagated down the chain of callers, an
147<code>'exception'</code> event is generated at each level.
148
149<P>
150For more information on code and frame objects, refer to the
151<em class="citetitle"><a
152 href="../ref/ref.html"
153 title="Python Reference Manual"
154 >Python Reference Manual</a></em>.
155
156<P>
157
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192<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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Full OpenSPARC design & verification tarball including full HDL.