195 lines
7.8 KiB
HTML
195 lines
7.8 KiB
HTML
|
<!DOCTYPE html>
|
||
|
|
<html>
|
||
|
|
<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<!-- This manual documents Guile version 3.0.10.
|
||
|
|
|
||
|
|
Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
|
||
|
|
Inc.
|
||
|
|
|
||
|
|
Copyright (C) 2021 Maxime Devos
|
||
|
|
|
||
|
|
Copyright (C) 2024 Tomas Volf
|
||
|
|
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with no
|
||
|
|
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
|
||
|
|
copy of the license is included in the section entitled "GNU Free
|
||
|
|
Documentation License." -->
|
||
|
|
<title>Interactive Debugging (Guile Reference Manual)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Interactive Debugging (Guile Reference Manual)">
|
||
|
|
<meta name="keywords" content="Interactive Debugging (Guile Reference Manual)">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content=".texi2any-real">
|
||
|
|
<meta name="viewport" content="width=device-width,initial-scale=1">
|
||
|
|
|
||
|
|
<link href="index.html" rel="start" title="Top">
|
||
|
|
<link href="Concept-Index.html" rel="index" title="Concept Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="Using-Guile-Interactively.html" rel="up" title="Using Guile Interactively">
|
||
|
|
<link href="Error-Handling.html" rel="prev" title="Error Handling">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
kbd.kbd {font-style: oblique}
|
||
|
|
span:hover a.copiable-link {visibility: visible}
|
||
|
|
ul.mark-bullet {list-style-type: disc}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<div class="subsection-level-extent" id="Interactive-Debugging">
|
||
|
|
<div class="nav-panel">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Error-Handling.html" accesskey="p" rel="prev">Error Handling</a>, Up: <a href="Using-Guile-Interactively.html" accesskey="u" rel="up">Using Guile Interactively</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<h4 class="subsection" id="Interactive-Debugging-1"><span>4.4.6 Interactive Debugging<a class="copiable-link" href="#Interactive-Debugging-1"> ¶</a></span></h4>
|
||
|
|
|
||
|
|
<p>A recursive debugging REPL exposes a number of other meta-commands that
|
||
|
|
inspect the state of the computation at the time of the error. These
|
||
|
|
commands allow you to
|
||
|
|
</p>
|
||
|
|
<ul class="itemize mark-bullet">
|
||
|
|
<li>display the Scheme call stack at the point where the error occurred;
|
||
|
|
|
||
|
|
</li><li>move up and down the call stack, to see in detail the expression being
|
||
|
|
evaluated, or the procedure being applied, in each <em class="dfn">frame</em>; and
|
||
|
|
|
||
|
|
</li><li>examine the values of variables and expressions in the context of each
|
||
|
|
frame.
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>See <a class="xref" href="Debug-Commands.html">Debug Commands</a>, for documentation of the individual
|
||
|
|
commands. This section aims to give more of a walkthrough of a typical
|
||
|
|
debugging session.
|
||
|
|
</p>
|
||
|
|
<p>First, we’re going to need a good error. Let’s try to macroexpand the
|
||
|
|
expression <code class="code">(unquote foo)</code>, outside of a <code class="code">quasiquote</code> form,
|
||
|
|
and see how the macroexpander reports this error.
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user)> (macroexpand '(unquote foo))
|
||
|
|
ERROR: In procedure macroexpand:
|
||
|
|
ERROR: unquote: expression not valid outside of quasiquote in (unquote foo)
|
||
|
|
Entering a new prompt. Type `,bt' for a backtrace or `,q' to continue.
|
||
|
|
scheme@(guile-user) [1]>
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The <code class="code">backtrace</code> command, which can also be invoked as <code class="code">bt</code>,
|
||
|
|
displays the call stack (aka backtrace) at the point where the debugger
|
||
|
|
was entered:
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [1]> ,bt
|
||
|
|
In ice-9/psyntax.scm:
|
||
|
|
1130:21 3 (chi-top (unquote foo) () ((top)) e (eval) (hygiene #))
|
||
|
|
1071:30 2 (syntax-type (unquote foo) () ((top)) #f #f (# #) #f)
|
||
|
|
1368:28 1 (chi-macro #<procedure de9360 at ice-9/psyntax.scm...> ...)
|
||
|
|
In unknown file:
|
||
|
|
0 (scm-error syntax-error macroexpand "~a: ~a in ~a" # #f)
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>A call stack consists of a sequence of stack <em class="dfn">frames</em>, with each
|
||
|
|
frame describing one procedure which is waiting to do something with the
|
||
|
|
values returned by another. Here we see that there are four frames on
|
||
|
|
the stack.
|
||
|
|
</p>
|
||
|
|
<p>Note that <code class="code">macroexpand</code> is not on the stack – it must have made a
|
||
|
|
tail call to <code class="code">chi-top</code>, as indeed we would find if we searched
|
||
|
|
<code class="code">ice-9/psyntax.scm</code> for its definition.
|
||
|
|
</p>
|
||
|
|
<p>When you enter the debugger, the innermost frame is selected, which
|
||
|
|
means that the commands for getting information about the “current”
|
||
|
|
frame, or for evaluating expressions in the context of the current
|
||
|
|
frame, will do so by default with respect to the innermost frame. To
|
||
|
|
select a different frame, so that these operations will apply to it
|
||
|
|
instead, use the <code class="code">up</code>, <code class="code">down</code> and <code class="code">frame</code> commands like
|
||
|
|
this:
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [1]> ,up
|
||
|
|
In ice-9/psyntax.scm:
|
||
|
|
1368:28 1 (chi-macro #<procedure de9360 at ice-9/psyntax.scm...> ...)
|
||
|
|
scheme@(guile-user) [1]> ,frame 3
|
||
|
|
In ice-9/psyntax.scm:
|
||
|
|
1130:21 3 (chi-top (unquote foo) () ((top)) e (eval) (hygiene #))
|
||
|
|
scheme@(guile-user) [1]> ,down
|
||
|
|
In ice-9/psyntax.scm:
|
||
|
|
1071:30 2 (syntax-type (unquote foo) () ((top)) #f #f (# #) #f)
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Perhaps we’re interested in what’s going on in frame 2, so we take a
|
||
|
|
look at its local variables:
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [1]> ,locals
|
||
|
|
Local variables:
|
||
|
|
$1 = e = (unquote foo)
|
||
|
|
$2 = r = ()
|
||
|
|
$3 = w = ((top))
|
||
|
|
$4 = s = #f
|
||
|
|
$5 = rib = #f
|
||
|
|
$6 = mod = (hygiene guile-user)
|
||
|
|
$7 = for-car? = #f
|
||
|
|
$8 = first = unquote
|
||
|
|
$9 = ftype = macro
|
||
|
|
$10 = fval = #<procedure de9360 at ice-9/psyntax.scm:2817:2 (x)>
|
||
|
|
$11 = fe = unquote
|
||
|
|
$12 = fw = ((top))
|
||
|
|
$13 = fs = #f
|
||
|
|
$14 = fmod = (hygiene guile-user)
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>All of the values are accessible by their value-history names
|
||
|
|
(<code class="code">$<var class="var">n</var></code>):
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [1]> $10
|
||
|
|
$15 = #<procedure de9360 at ice-9/psyntax.scm:2817:2 (x)>
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>We can even invoke the procedure at the REPL directly:
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [1]> ($10 'not-going-to-work)
|
||
|
|
ERROR: In procedure macroexpand:
|
||
|
|
ERROR: source expression failed to match any pattern in not-going-to-work
|
||
|
|
Entering a new prompt. Type `,bt' for a backtrace or `,q' to continue.
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Well at this point we’ve caused an error within an error. Let’s just
|
||
|
|
quit back to the top level:
|
||
|
|
</p>
|
||
|
|
<div class="example lisp">
|
||
|
|
<pre class="lisp-preformatted">scheme@(guile-user) [2]> ,q
|
||
|
|
scheme@(guile-user) [1]> ,q
|
||
|
|
scheme@(guile-user)>
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Finally, as a word to the wise: hackers close their REPL prompts with
|
||
|
|
<kbd class="kbd">C-d</kbd>.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<div class="nav-panel">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Error-Handling.html">Error Handling</a>, Up: <a href="Using-Guile-Interactively.html">Using Guile Interactively</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|