<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Copyright (C) 1988-2020 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. 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Two examples are: <code>set follow-fork</code> and <code>set charset</code>. Setting these parameters influences certain behavior in <small>GDB</small>. Similarly, you can define parameters that can be used to influence behavior in custom Guile scripts and commands. </p> <p>A new parameter is defined with the <code>make-parameter</code> Guile function, and added to <small>GDB</small> with the <code>register-parameter!</code> Guile function. This two-step approach is taken to separate out the side-effect of adding the parameter to <small>GDB</small> from <code>make-parameter</code>. </p> <p>Parameters are exposed to the user via the <code>set</code> and <code>show</code> commands. See <a href="Help.html#Help">Help</a>. </p> <dl> <dt><a name="index-_0028make_002dparameter"></a>Scheme Procedure: <strong>(make-parameter</strong> <em>name <span class="roman">[</span>#:command-class command-class<span class="roman">]</span> <span class="roman">[</span>#:parameter-type parameter-type] <span class="roman">[</span>#:enum-list enum-list<span class="roman">]</span> <span class="roman">[</span>#:set-func set-func] <span class="roman">[</span>#:show-func show-func] <span class="roman">[</span>#:doc doc] <span class="roman">[</span>#:set-doc set-doc] <span class="roman">[</span>#:show-doc show-doc] <span class="roman">[</span>#:initial-value initial-value])</em></dt> <dd> <p>The argument <var>name</var> is the name of the new parameter. If <var>name</var> consists of multiple words, then the initial words are looked for as prefix parameters. An example of this can be illustrated with the <code>set print</code> set of parameters. If <var>name</var> is <code>print foo</code>, then <code>print</code> will be searched as the prefix parameter. In this case the parameter can subsequently be accessed in <small>GDB</small> as <code>set print foo</code>. If <var>name</var> consists of multiple words, and no prefix parameter group can be found, an exception is raised. </p> <p>The result is the <code><gdb:parameter></code> object representing the parameter. The parameter is not usable until it has been registered with <small>GDB</small> with <code>register-parameter!</code>. </p> <p>The rest of the arguments are optional. </p> <p>The argument <var>command-class</var> should be one of the ‘<samp>COMMAND_</samp>’ constants (see <a href="Commands-In-Guile.html#Commands-In-Guile">Commands In Guile</a>). This argument tells <small>GDB</small> how to categorize the new parameter in the help system. The default is <code>COMMAND_NONE</code>. </p> <p>The argument <var>parameter-type</var> should be one of the ‘<samp>PARAM_</samp>’ constants defined below. This argument tells <small>GDB</small> the type of the new parameter; this information is used for input validation and completion. The default is <code>PARAM_BOOLEAN</code>. </p> <p>If <var>parameter-type</var> is <code>PARAM_ENUM</code>, then <var>enum-list</var> must be a list of strings. These strings represent the possible values for the parameter. </p> <p>If <var>parameter-type</var> is not <code>PARAM_ENUM</code>, then the presence of <var>enum-list</var> will cause an exception to be thrown. </p> <p>The argument <var>set-func</var> is a function of one argument: <var>self</var> which is the <code><gdb:parameter></code> object representing the parameter. <small>GDB</small> will call this function when a <var>parameter</var>’s value has been changed via the <code>set</code> API (for example, <kbd>set foo off</kbd>). The value of the parameter has already been set to the new value. This function must return a string to be displayed to the user. <small>GDB</small> will add a trailing newline if the string is non-empty. <small>GDB</small> generally doesn’t print anything when a parameter is set, thus typically this function should return ‘<samp>""</samp>’. A non-empty string result should typically be used for displaying warnings and errors. </p> <p>The argument <var>show-func</var> is a function of two arguments: <var>self</var> which is the <code><gdb:parameter></code> object representing the parameter, and <var>svalue</var> which is the string representation of the current value. <small>GDB</small> will call this function when a <var>parameter</var>’s <code>show</code> API has been invoked (for example, <kbd>show foo</kbd>). This function must return a string, and will be displayed to the user. <small>GDB</small> will add a trailing newline. </p> <p>The argument <var>doc</var> is the help text for the new parameter. If there is no documentation string, a default value is used. </p> <p>The argument <var>set-doc</var> is the help text for this parameter’s <code>set</code> command. </p> <p>The argument <var>show-doc</var> is the help text for this parameter’s <code>show</code> command. </p> <p>The argument <var>initial-value</var> specifies the initial value of the parameter. If it is a function, it takes one parameter, the <code><gdb:parameter></code> object and its result is used as the initial value of the parameter. The initial value must be valid for the parameter type, otherwise an exception is thrown. </p></dd></dl> <dl> <dt><a name="index-register_002dparameter_0021"></a>Scheme Procedure: <strong>register-parameter!</strong> <em>parameter</em></dt> <dd><p>Add <var>parameter</var>, a <code><gdb:parameter></code> object, to <small>GDB</small>’s list of parameters. It is an error to register a parameter more than once. The result is unspecified. </p></dd></dl> <dl> <dt><a name="index-parameter_003f"></a>Scheme Procedure: <strong>parameter?</strong> <em>object</em></dt> <dd><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:parameter></code> object. Otherwise return <code>#f</code>. </p></dd></dl> <dl> <dt><a name="index-parameter_002dvalue"></a>Scheme Procedure: <strong>parameter-value</strong> <em>parameter</em></dt> <dd><p>Return the value of <var>parameter</var> which may either be a <code><gdb:parameter></code> object or a string naming the parameter. </p></dd></dl> <dl> <dt><a name="index-set_002dparameter_002dvalue_0021"></a>Scheme Procedure: <strong>set-parameter-value!</strong> <em>parameter new-value</em></dt> <dd><p>Assign <var>parameter</var> the value of <var>new-value</var>. The argument <var>parameter</var> must be an object of type <code><gdb:parameter></code>. <small>GDB</small> does validation when assignments are made. </p></dd></dl> <p>When a new parameter is defined, its type must be specified. The available types are represented by constants defined in the <code>gdb</code> module: </p> <dl compact="compact"> <dt><code>PARAM_BOOLEAN</code> <a name="index-PARAM_005fBOOLEAN-1"></a> </dt> <dd><p>The value is a plain boolean. The Guile boolean values, <code>#t</code> and <code>#f</code> are the only valid values. </p> </dd> <dt><code>PARAM_AUTO_BOOLEAN</code> <a name="index-PARAM_005fAUTO_005fBOOLEAN-1"></a> </dt> <dd><p>The value has three possible states: true, false, and ‘<samp>auto</samp>’. In Guile, true and false are represented using boolean constants, and ‘<samp>auto</samp>’ is represented using <code>#:auto</code>. </p> </dd> <dt><code>PARAM_UINTEGER</code> <a name="index-PARAM_005fUINTEGER-1"></a> </dt> <dd><p>The value is an unsigned integer. The value of 0 should be interpreted to mean “unlimited”. </p> </dd> <dt><code>PARAM_ZINTEGER</code> <a name="index-PARAM_005fZINTEGER-1"></a> </dt> <dd><p>The value is an integer. </p> </dd> <dt><code>PARAM_ZUINTEGER</code> <a name="index-PARAM_005fZUINTEGER-1"></a> </dt> <dd><p>The value is an unsigned integer. </p> </dd> <dt><code>PARAM_ZUINTEGER_UNLIMITED</code> <a name="index-PARAM_005fZUINTEGER_005fUNLIMITED-1"></a> </dt> <dd><p>The value is an integer in the range ‘<samp>[0, INT_MAX]</samp>’. A value of ‘<samp>-1</samp>’ means “unlimited”, and other negative numbers are not allowed. </p> </dd> <dt><code>PARAM_STRING</code> <a name="index-PARAM_005fSTRING-1"></a> </dt> <dd><p>The value is a string. When the user modifies the string, any escape sequences, such as ‘<samp>\t</samp>’, ‘<samp>\f</samp>’, and octal escapes, are translated into corresponding characters and encoded into the current host charset. </p> </dd> <dt><code>PARAM_STRING_NOESCAPE</code> <a name="index-PARAM_005fSTRING_005fNOESCAPE-1"></a> </dt> <dd><p>The value is a string. When the user modifies the string, escapes are passed through untranslated. </p> </dd> <dt><code>PARAM_OPTIONAL_FILENAME</code> <a name="index-PARAM_005fOPTIONAL_005fFILENAME-1"></a> </dt> <dd><p>The value is a either a filename (a string), or <code>#f</code>. </p> </dd> <dt><code>PARAM_FILENAME</code> <a name="index-PARAM_005fFILENAME-1"></a> </dt> <dd><p>The value is a filename. This is just like <code>PARAM_STRING_NOESCAPE</code>, but uses file names for completion. </p> </dd> <dt><code>PARAM_ENUM</code> <a name="index-PARAM_005fENUM-1"></a> </dt> <dd><p>The value is a string, which must be one of a collection of string constants provided when the parameter is created. </p></dd> </dl> <div class="footnote"> <hr> <h4 class="footnotes-heading">Footnotes</h4> <h3><a name="FOOT18" href="#DOCF18">(18)</a></h3> <p>Note that <small>GDB</small> parameters must not be confused with Guileâs parameter objects (see <a href="http://www.gnu.org/software/guile/manual/html_node/Parameters.html#Parameters">Parameters</a> in <cite>GNU Guile Reference Manual</cite>).</p> </div> <hr> <div class="header"> <p> Next: <a href="Progspaces-In-Guile.html#Progspaces-In-Guile" accesskey="n" rel="next">Progspaces In Guile</a>, Previous: <a href="Commands-In-Guile.html#Commands-In-Guile" accesskey="p" rel="prev">Commands In Guile</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>