Sophie: sbcl-1.0.31-1mdv2010.0 i586

sbcl-1.0.31-1mdv2010.0.i586.rpm

<html lang="en">
<head>
<title>Debugger Invocation - SBCL 1.0.31 User Manual</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="SBCL 1.0.31 User Manual">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Debugger-Entry.html#Debugger-Entry" title="Debugger Entry">
<link rel="prev" href="Debugger-Banner.html#Debugger-Banner" title="Debugger Banner">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--

     This manual is part of the SBCL software system. See the `README'
     file for more information.

     This manual is largely derived from the manual for the CMUCL
     system, which was produced at Carnegie Mellon University and later
     released into the public domain. This manual is in the public
     domain and is provided with absolutely no warranty. See the
     `COPYING' and `CREDITS' files for more information.
   -->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
  pre.display { font-family:inherit }
  pre.format  { font-family:inherit }
  pre.smalldisplay { font-family:inherit; font-size:smaller }
  pre.smallformat  { font-family:inherit; font-size:smaller }
  pre.smallexample { font-size:smaller }
  pre.smalllisp    { font-size:smaller }
  span.sc    { font-variant:small-caps }
  span.roman { font-family:serif; font-weight:normal; } 
  span.sansserif { font-family:sans-serif; font-weight:normal; } 
--></style>
</head>
<body>
<div class="node">
<a name="Debugger-Invocation"></a>
<p>
Previous:&nbsp;<a rel="previous" accesskey="p" href="Debugger-Banner.html#Debugger-Banner">Debugger Banner</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Debugger-Entry.html#Debugger-Entry">Debugger Entry</a>
<hr>
</div>

<!-- node-name,  next,  previous,  up -->
<h4 class="subsection">5.1.2 Debugger Invocation</h4>

<p>The debugger is invoked when:

     <ul>
<li><code>error</code> is called, and the condition it signals is not handled.

     <li><code>break</code> is called, or <code>signal</code> is called with a condition
that matches the current <code>*break-on-signals*</code>.

     <li>the debugger is explicitly entered with the <code>invoke-debugger</code>
function.

   </ul>

   <p>When the debugger is invoked by a condition, ANSI mandates that the
value of <code>*debugger-hook*</code>, if any, be called with two arguments:
the condition that caused the debugger to be invoked and the previous
value of <code>*debugger-hook*</code>. When this happens,
<code>*debugger-hook*</code> is bound to NIL to prevent recursive errors. 
However, ANSI also mandates that <code>*debugger-hook*</code> not be invoked
when the debugger is to be entered by the <code>break</code> function. For
users who wish to provide an alternate debugger interface (and thus
catch <code>break</code> entries into the debugger), SBCL provides
<code>sb-ext:*invoke-debugger-hook*</code>, which is invoked during any
entry into the debugger.

   <p><a name="Variable-sb_002dext_003a_002ainvoke_002ddebugger_002dhook_002a"></a>

<div class="defun">
&mdash; Variable: <b>sb-ext:*invoke-debugger-hook*</b><var><a name="index-sb_002dext_003a_002ainvoke_002ddebugger_002dhook_002a-61"></a></var><br>
<blockquote><p><a name="index-sb_002dext_003a_002ainvoke_002ddebugger_002dhook_002a-62"></a>This is either <code>nil</code> or a designator for a function of two arguments,
   to be run when the debugger is about to be entered.  The function is
   run with <code>*invoke-debugger-hook*</code> bound to <code>nil</code> to minimize recursive
   errors, and receives as arguments the condition that triggered
   debugger entry and the previous value of <code>*invoke-debugger-hook*</code>

        <p>This mechanism is an <code>sbcl</code> extension similar to the standard <code>*debugger-hook*</code>. 
   In contrast to <code>*debugger-hook*</code>, it is observed by <code>invoke-debugger</code> even when
   called by <code>break</code>. 
</p></blockquote></div>

   </body></html>