| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- Copyright (C) 1988-2015 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 5.2, 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="prev" 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="prev">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="prev">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> |
