<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
<html>
|
<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc.
|
|
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 the
|
Invariant Sections being "Free Software" and "Free Software Needs
|
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
|
and with the Back-Cover Texts as in (a) below.
|
|
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
|
this GNU Manual. Buying copies from GNU Press supports the FSF in
|
developing GNU and promoting software freedom." -->
|
<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ -->
|
<head>
|
<title>Debugging with GDB: Selecting Guile Pretty-Printers</title>
|
|
<meta name="description" content="Debugging with GDB: Selecting Guile Pretty-Printers">
|
<meta name="keywords" content="Debugging with GDB: Selecting Guile Pretty-Printers">
|
<meta name="resource-type" content="document">
|
<meta name="distribution" content="global">
|
<meta name="Generator" content="makeinfo">
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
<link href="index.html#Top" rel="start" title="Top">
|
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
<link href="Guile-API.html#Guile-API" rel="up" title="Guile API">
|
<link href="Writing-a-Guile-Pretty_002dPrinter.html#Writing-a-Guile-Pretty_002dPrinter" rel="next" title="Writing a Guile Pretty-Printer">
|
<link href="Guile-Pretty-Printing-API.html#Guile-Pretty-Printing-API" rel="previous" title="Guile Pretty Printing API">
|
<style type="text/css">
|
<!--
|
a.summary-letter {text-decoration: none}
|
blockquote.smallquotation {font-size: smaller}
|
div.display {margin-left: 3.2em}
|
div.example {margin-left: 3.2em}
|
div.indentedblock {margin-left: 3.2em}
|
div.lisp {margin-left: 3.2em}
|
div.smalldisplay {margin-left: 3.2em}
|
div.smallexample {margin-left: 3.2em}
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
div.smalllisp {margin-left: 3.2em}
|
kbd {font-style:oblique}
|
pre.display {font-family: inherit}
|
pre.format {font-family: inherit}
|
pre.menu-comment {font-family: serif}
|
pre.menu-preformatted {font-family: serif}
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
pre.smallexample {font-size: smaller}
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
pre.smalllisp {font-size: smaller}
|
span.nocodebreak {white-space:nowrap}
|
span.nolinebreak {white-space:nowrap}
|
span.roman {font-family:serif; font-weight:normal}
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
ul.no-bullet {list-style: none}
|
-->
|
</style>
|
|
|
</head>
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
<a name="Selecting-Guile-Pretty_002dPrinters"></a>
|
<div class="header">
|
<p>
|
Next: <a href="Writing-a-Guile-Pretty_002dPrinter.html#Writing-a-Guile-Pretty_002dPrinter" accesskey="n" rel="next">Writing a Guile Pretty-Printer</a>, Previous: <a href="Guile-Pretty-Printing-API.html#Guile-Pretty-Printing-API" accesskey="p" rel="previous">Guile Pretty Printing API</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile 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>
|
</div>
|
<hr>
|
<a name="Selecting-Guile-Pretty_002dPrinters-1"></a>
|
<h4 class="subsubsection">23.3.3.9 Selecting Guile Pretty-Printers</h4>
|
<a name="index-selecting-guile-pretty_002dprinters"></a>
|
|
<p>There are three sets of pretty-printers that <small>GDB</small> searches:
|
</p>
|
<ul>
|
<li> Per-objfile list of pretty-printers (see <a href="Objfiles-In-Guile.html#Objfiles-In-Guile">Objfiles In Guile</a>).
|
</li><li> Per-progspace list of pretty-printers (see <a href="Progspaces-In-Guile.html#Progspaces-In-Guile">Progspaces In Guile</a>).
|
</li><li> The global list of pretty-printers (see <a href="Guile-Pretty-Printing-API.html#Guile-Pretty-Printing-API">Guile Pretty Printing API</a>).
|
These printers are available when debugging any inferior.
|
</li></ul>
|
|
<p>Pretty-printer lookup is done by passing the value to be printed to the
|
lookup function of each enabled object in turn.
|
Lookup stops when a lookup function returns a non-<code>#f</code> value
|
or when the list is exhausted.
|
Lookup functions must return either a <code><gdb:pretty-printer-worker></code>
|
object or <code>#f</code>. Otherwise an exception is thrown.
|
</p>
|
<p><small>GDB</small> first checks the result of <code>objfile-pretty-printers</code>
|
of each <code><gdb:objfile></code> in the current program space and iteratively
|
calls each enabled lookup function in the list for that <code><gdb:objfile></code>
|
until a non-<code>#f</code> object is returned.
|
If no pretty-printer is found in the objfile lists, <small>GDB</small> then
|
searches the result of <code>progspace-pretty-printers</code> of the current
|
program space, calling each enabled function until a non-<code>#f</code> object
|
is returned.
|
After these lists have been exhausted, it tries the global pretty-printers
|
list, obtained with <code>pretty-printers</code>, again calling each enabled
|
function until a non-<code>#f</code> object is returned.
|
</p>
|
<p>The order in which the objfiles are searched is not specified. For a
|
given list, functions are always invoked from the head of the list,
|
and iterated over sequentially until the end of the list, or a
|
<code><gdb:pretty-printer-worker></code> object is returned.
|
</p>
|
<p>For various reasons a pretty-printer may not work.
|
For example, the underlying data structure may have changed and
|
the pretty-printer is out of date.
|
</p>
|
<p>The consequences of a broken pretty-printer are severe enough that
|
<small>GDB</small> provides support for enabling and disabling individual
|
printers. For example, if <code>print frame-arguments</code> is on,
|
a backtrace can become highly illegible if any argument is printed
|
with a broken printer.
|
</p>
|
<p>Pretty-printers are enabled and disabled from Scheme by calling
|
<code>set-pretty-printer-enabled!</code>.
|
See <a href="Guile-Pretty-Printing-API.html#Guile-Pretty-Printing-API">Guile Pretty Printing API</a>.
|
</p>
|
<hr>
|
<div class="header">
|
<p>
|
Next: <a href="Writing-a-Guile-Pretty_002dPrinter.html#Writing-a-Guile-Pretty_002dPrinter" accesskey="n" rel="next">Writing a Guile Pretty-Printer</a>, Previous: <a href="Guile-Pretty-Printing-API.html#Guile-Pretty-Printing-API" accesskey="p" rel="previous">Guile Pretty Printing API</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile 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>
|
</div>
|
|
|
|
</body>
|
</html>
|
