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| <h5 class="subsubsection">23.3.3.12 Parameters In Guile</h5> |
| |
| <p><a name="index-parameters-in-guile-2635"></a><a name="index-guile-parameters-2636"></a><a name="index-Parameter-2637"></a>You can implement new <span class="sc">gdb</span> <dfn>parameters</dfn> using Guile |
| <a rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a>. |
| |
| <p>There are many parameters that already exist and can be set in |
| <span class="sc">gdb</span>. Two examples are: <code>set follow-fork</code> and |
| <code>set charset</code>. Setting these parameters influences certain |
| behavior in <span class="sc">gdb</span>. Similarly, you can define parameters that |
| can be used to influence behavior in custom Guile scripts and commands. |
| |
| <p>A new parameter is defined with the <code>make-parameter</code> Guile function, |
| and added to <span class="sc">gdb</span> 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 <span class="sc">gdb</span> from <code>make-parameter</code>. |
| |
| <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>. |
| |
| <!-- TODO line length --> |
| <div class="defun"> |
| — Scheme Procedure: <b>(</b><var>make-parameter name </var><span class="roman">[</span><var>#:command-class command-class</var><span class="roman">]</span> <span class="roman">[</span><var>#:parameter-type parameter-type</var>] <span class="roman">[</span><var>#:enum-list enum-list</var><span class="roman">]</span> <span class="roman">[</span><var>#:set-func set-func</var>] <span class="roman">[</span><var>#:show-func show-func</var>] <span class="roman">[</span><var>#:doc doc</var>] <span class="roman">[</span><var>#:set-doc set-doc</var>] <span class="roman">[</span><var>#:show-doc show-doc</var>] <span class="roman">[</span><var>#:initial-value initial-value</var>])<var><a name="index-g_t_0028-2638"></a></var><br> |
| <blockquote> |
| <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 |
| <span class="sc">gdb</span> 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>The result is the <code><gdb:parameter></code> object representing the parameter. |
| The parameter is not usable until it has been registered with <span class="sc">gdb</span> |
| with <code>register-parameter!</code>. |
| |
| <p>The rest of the arguments are optional. |
| |
| <p>The argument <var>command-class</var> should be one of the ‘<samp><span class="samp">COMMAND_</span></samp>’ constants |
| (see <a href="Commands-In-Guile.html#Commands-In-Guile">Commands In Guile</a>). This argument tells <span class="sc">gdb</span> how to |
| categorize the new parameter in the help system. |
| The default is <code>COMMAND_NONE</code>. |
| |
| <p>The argument <var>parameter-type</var> should be one of the ‘<samp><span class="samp">PARAM_</span></samp>’ constants |
| defined below. This argument tells <span class="sc">gdb</span> the type of the new |
| parameter; this information is used for input validation and |
| completion. The default is <code>PARAM_BOOLEAN</code>. |
| |
| <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>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>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. |
| <span class="sc">gdb</span> 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. |
| <span class="sc">gdb</span> will add a trailing newline if the string is non-empty. |
| <span class="sc">gdb</span> generally doesn't print anything when a parameter is set, |
| thus typically this function should return ‘<samp><span class="samp">""</span></samp>’. |
| A non-empty string result should typically be used for displaying warnings |
| and errors. |
| |
| <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. |
| <span class="sc">gdb</span> 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. |
| <span class="sc">gdb</span> will add a trailing newline. |
| |
| <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>The argument <var>set-doc</var> is the help text for this parameter's |
| <code>set</code> command. |
| |
| <p>The argument <var>show-doc</var> is the help text for this parameter's |
| <code>show</code> command. |
| |
| <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></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>register-parameter!</b><var> parameter<a name="index-register_002dparameter_0021-2639"></a></var><br> |
| <blockquote><p>Add <var>parameter</var>, a <code><gdb:parameter></code> object, to <span class="sc">gdb</span>'s |
| list of parameters. |
| It is an error to register a parameter more than once. |
| The result is unspecified. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>parameter?</b><var> object<a name="index-parameter_003f-2640"></a></var><br> |
| <blockquote><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:parameter></code> object. |
| Otherwise return <code>#f</code>. |
| </p></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>parameter-value</b><var> parameter<a name="index-parameter_002dvalue-2641"></a></var><br> |
| <blockquote><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></blockquote></div> |
| |
| <div class="defun"> |
| — Scheme Procedure: <b>set-parameter-value!</b><var> parameter new-value<a name="index-set_002dparameter_002dvalue_0021-2642"></a></var><br> |
| <blockquote><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>. |
| <span class="sc">gdb</span> does validation when assignments are made. |
| </p></blockquote></div> |
| |
| <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: |
| |
| <dl> |
| <dt><code>PARAM_BOOLEAN</code><a name="index-PARAM_005fBOOLEAN-2643"></a><dd>The value is a plain boolean. The Guile boolean values, <code>#t</code> |
| and <code>#f</code> are the only valid values. |
| |
| <br><dt><code>PARAM_AUTO_BOOLEAN</code><a name="index-PARAM_005fAUTO_005fBOOLEAN-2644"></a><dd>The value has three possible states: true, false, and ‘<samp><span class="samp">auto</span></samp>’. In |
| Guile, true and false are represented using boolean constants, and |
| ‘<samp><span class="samp">auto</span></samp>’ is represented using <code>#:auto</code>. |
| |
| <br><dt><code>PARAM_UINTEGER</code><a name="index-PARAM_005fUINTEGER-2645"></a><dd>The value is an unsigned integer. The value of 0 should be |
| interpreted to mean “unlimited”. |
| |
| <br><dt><code>PARAM_ZINTEGER</code><a name="index-PARAM_005fZINTEGER-2646"></a><dd>The value is an integer. |
| |
| <br><dt><code>PARAM_ZUINTEGER</code><a name="index-PARAM_005fZUINTEGER-2647"></a><dd>The value is an unsigned integer. |
| |
| <br><dt><code>PARAM_ZUINTEGER_UNLIMITED</code><a name="index-PARAM_005fZUINTEGER_005fUNLIMITED-2648"></a><dd>The value is an integer in the range ‘<samp><span class="samp">[0, INT_MAX]</span></samp>’. |
| A value of ‘<samp><span class="samp">-1</span></samp>’ means “unlimited”, and other negative |
| numbers are not allowed. |
| |
| <br><dt><code>PARAM_STRING</code><a name="index-PARAM_005fSTRING-2649"></a><dd>The value is a string. When the user modifies the string, any escape |
| sequences, such as ‘<samp><span class="samp">\t</span></samp>’, ‘<samp><span class="samp">\f</span></samp>’, and octal escapes, are |
| translated into corresponding characters and encoded into the current |
| host charset. |
| |
| <br><dt><code>PARAM_STRING_NOESCAPE</code><a name="index-PARAM_005fSTRING_005fNOESCAPE-2650"></a><dd>The value is a string. When the user modifies the string, escapes are |
| passed through untranslated. |
| |
| <br><dt><code>PARAM_OPTIONAL_FILENAME</code><a name="index-PARAM_005fOPTIONAL_005fFILENAME-2651"></a><dd>The value is a either a filename (a string), or <code>#f</code>. |
| |
| <br><dt><code>PARAM_FILENAME</code><a name="index-PARAM_005fFILENAME-2652"></a><dd>The value is a filename. This is just like |
| <code>PARAM_STRING_NOESCAPE</code>, but uses file names for completion. |
| |
| <br><dt><code>PARAM_ENUM</code><a name="index-PARAM_005fENUM-2653"></a><dd>The value is a string, which must be one of a collection of string |
| constants provided when the parameter is created. |
| </dl> |
| |
| <div class="footnote"> |
| <hr> |
| <h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> Note that <span class="sc">gdb</span> parameters must not be confused with |
| Guile’s parameter objects (see <a href="../guile/Parameters.html#Parameters">Parameters</a>).</p> |
| |
| <hr></div> |
| |
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