You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
501 lines
25 KiB
HTML
501 lines
25 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2019 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 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Values From Inferior In Guile (Debugging with GDB)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Values From Inferior In Guile (Debugging with GDB)">
|
||
|
|
<meta name="keywords" content="Values From Inferior In Guile (Debugging with GDB)">
|
||
|
|
<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="Arithmetic-In-Guile.html#Arithmetic-In-Guile" rel="next" title="Arithmetic In Guile">
|
||
|
|
<link href="Guile-Exception-Handling.html#Guile-Exception-Handling" rel="prev" title="Guile Exception Handling">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
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.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Values-From-Inferior-In-Guile"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Arithmetic-In-Guile.html#Arithmetic-In-Guile" accesskey="n" rel="next">Arithmetic In Guile</a>, Previous: <a href="Guile-Exception-Handling.html#Guile-Exception-Handling" accesskey="p" rel="prev">Guile Exception Handling</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="Values-From-Inferior-In-Guile-1"></a>
|
||
|
|
<h4 class="subsubsection">23.3.3.5 Values From Inferior In Guile</h4>
|
||
|
|
<a name="index-values-from-inferior_002c-in-guile"></a>
|
||
|
|
<a name="index-guile_002c-working-with-values-from-inferior"></a>
|
||
|
|
|
||
|
|
<a name="index-_003cgdb_003avalue_003e"></a>
|
||
|
|
<p><small>GDB</small> provides values it obtains from the inferior program in
|
||
|
|
an object of type <code><gdb:value></code>. <small>GDB</small> uses this object
|
||
|
|
for its internal bookkeeping of the inferior’s values, and for
|
||
|
|
fetching values when necessary.
|
||
|
|
</p>
|
||
|
|
<p><small>GDB</small> does not memoize <code><gdb:value></code> objects.
|
||
|
|
<code>make-value</code> always returns a fresh object.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(gdb) guile (eq? (make-value 1) (make-value 1))
|
||
|
|
$1 = #f
|
||
|
|
(gdb) guile (equal? (make-value 1) (make-value 1))
|
||
|
|
$1 = #t
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>A <code><gdb:value></code> that represents a function can be executed via
|
||
|
|
inferior function call with <code>value-call</code>.
|
||
|
|
Any arguments provided to the call must match the function’s prototype,
|
||
|
|
and must be provided in the order specified by that prototype.
|
||
|
|
</p>
|
||
|
|
<p>For example, <code>some-val</code> is a <code><gdb:value></code> instance
|
||
|
|
representing a function that takes two integers as arguments. To
|
||
|
|
execute this function, call it like so:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define result (value-call some-val 10 20))
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Any values returned from a function call are <code><gdb:value></code> objects.
|
||
|
|
</p>
|
||
|
|
<p>Note: Unlike Python scripting in <small>GDB</small>,
|
||
|
|
inferior values that are simple scalars cannot be used directly in
|
||
|
|
Scheme expressions that are valid for the value’s data type.
|
||
|
|
For example, <code>(+ (parse-and-eval "int_variable") 2)</code> does not work.
|
||
|
|
And inferior values that are structures or instances of some class cannot
|
||
|
|
be accessed using any special syntax, instead <code>value-field</code> must be used.
|
||
|
|
</p>
|
||
|
|
<p>The following value-related procedures are provided by the
|
||
|
|
<code>(gdb)</code> module.
|
||
|
|
</p>
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_003f"></a>Scheme Procedure: <strong>value?</strong> <em>object</em></dt>
|
||
|
|
<dd><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:value></code> object.
|
||
|
|
Otherwise return <code>#f</code>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-make_002dvalue"></a>Scheme Procedure: <strong>make-value</strong> <em>value <span class="roman">[</span>#:type type<span class="roman">]</span></em></dt>
|
||
|
|
<dd><p>Many Scheme values can be converted directly to a <code><gdb:value></code>
|
||
|
|
with this procedure. If <var>type</var> is specified, the result is a value
|
||
|
|
of this type, and if <var>value</var> can’t be represented with this type
|
||
|
|
an exception is thrown. Otherwise the type of the result is determined from
|
||
|
|
<var>value</var> as described below.
|
||
|
|
</p>
|
||
|
|
<p>See <a href="Architectures-In-Guile.html#Architectures-In-Guile">Architectures In Guile</a>, for a list of the builtin
|
||
|
|
types for an architecture.
|
||
|
|
</p>
|
||
|
|
<p>Here’s how Scheme values are converted when <var>type</var> argument to
|
||
|
|
<code>make-value</code> is not specified:
|
||
|
|
</p>
|
||
|
|
<dl compact="compact">
|
||
|
|
<dt>Scheme boolean</dt>
|
||
|
|
<dd><p>A Scheme boolean is converted the boolean type for the current language.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>Scheme integer</dt>
|
||
|
|
<dd><p>A Scheme integer is converted to the first of a C <code>int</code>,
|
||
|
|
<code>unsigned int</code>, <code>long</code>, <code>unsigned long</code>,
|
||
|
|
<code>long long</code> or <code>unsigned long long</code> type
|
||
|
|
for the current architecture that can represent the value.
|
||
|
|
</p>
|
||
|
|
<p>If the Scheme integer cannot be represented as a target integer
|
||
|
|
an <code>out-of-range</code> exception is thrown.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>Scheme real</dt>
|
||
|
|
<dd><p>A Scheme real is converted to the C <code>double</code> type for the
|
||
|
|
current architecture.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>Scheme string</dt>
|
||
|
|
<dd><p>A Scheme string is converted to a string in the current target
|
||
|
|
language using the current target encoding.
|
||
|
|
Characters that cannot be represented in the current target encoding
|
||
|
|
are replaced with the corresponding escape sequence. This is Guile’s
|
||
|
|
<code>SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE</code> conversion strategy
|
||
|
|
(see <a href="http://www.gnu.org/software/guile/manual/html_node/Strings.html#Strings">Strings</a> in <cite>GNU Guile Reference Manual</cite>).
|
||
|
|
</p>
|
||
|
|
<p>Passing <var>type</var> is not supported in this case,
|
||
|
|
if it is provided a <code>wrong-type-arg</code> exception is thrown.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt><code><gdb:lazy-string></code></dt>
|
||
|
|
<dd><p>If <var>value</var> is a <code><gdb:lazy-string></code> object (see <a href="Lazy-Strings-In-Guile.html#Lazy-Strings-In-Guile">Lazy Strings In Guile</a>), then the <code>lazy-string->value</code> procedure is called, and
|
||
|
|
its result is used.
|
||
|
|
</p>
|
||
|
|
<p>Passing <var>type</var> is not supported in this case,
|
||
|
|
if it is provided a <code>wrong-type-arg</code> exception is thrown.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt>Scheme bytevector</dt>
|
||
|
|
<dd><p>If <var>value</var> is a Scheme bytevector and <var>type</var> is provided,
|
||
|
|
<var>value</var> must be the same size, in bytes, of values of type <var>type</var>,
|
||
|
|
and the result is essentially created by using <code>memcpy</code>.
|
||
|
|
</p>
|
||
|
|
<p>If <var>value</var> is a Scheme bytevector and <var>type</var> is not provided,
|
||
|
|
the result is an array of type <code>uint8</code> of the same length.
|
||
|
|
</p></dd>
|
||
|
|
</dl>
|
||
|
|
</dd></dl>
|
||
|
|
|
||
|
|
<a name="index-optimized-out-value-in-guile"></a>
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002doptimized_002dout_003f"></a>Scheme Procedure: <strong>value-optimized-out?</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return <code>#t</code> if the compiler optimized out <var>value</var>,
|
||
|
|
thus it is not available for fetching from the inferior.
|
||
|
|
Otherwise return <code>#f</code>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002daddress"></a>Scheme Procedure: <strong>value-address</strong> <em>value</em></dt>
|
||
|
|
<dd><p>If <var>value</var> is addressable, returns a
|
||
|
|
<code><gdb:value></code> object representing the address.
|
||
|
|
Otherwise, <code>#f</code> is returned.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dtype"></a>Scheme Procedure: <strong>value-type</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return the type of <var>value</var> as a <code><gdb:type></code> object
|
||
|
|
(see <a href="Types-In-Guile.html#Types-In-Guile">Types In Guile</a>).
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002ddynamic_002dtype"></a>Scheme Procedure: <strong>value-dynamic-type</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return the dynamic type of <var>value</var>. This uses C<tt>++</tt> run-time
|
||
|
|
type information (<acronym>RTTI</acronym>) to determine the dynamic type of the
|
||
|
|
value. If the value is of class type, it will return the class in
|
||
|
|
which the value is embedded, if any. If the value is of pointer or
|
||
|
|
reference to a class type, it will compute the dynamic type of the
|
||
|
|
referenced object, and return a pointer or reference to that type,
|
||
|
|
respectively. In all other cases, it will return the value’s static
|
||
|
|
type.
|
||
|
|
</p>
|
||
|
|
<p>Note that this feature will only work when debugging a C<tt>++</tt> program
|
||
|
|
that includes <acronym>RTTI</acronym> for the object in question. Otherwise,
|
||
|
|
it will just return the static type of the value as in <kbd>ptype foo</kbd>.
|
||
|
|
See <a href="Symbols.html#Symbols">ptype</a>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dcast"></a>Scheme Procedure: <strong>value-cast</strong> <em>value type</em></dt>
|
||
|
|
<dd><p>Return a new instance of <code><gdb:value></code> that is the result of
|
||
|
|
casting <var>value</var> to the type described by <var>type</var>, which must
|
||
|
|
be a <code><gdb:type></code> object. If the cast cannot be performed for some
|
||
|
|
reason, this method throws an exception.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002ddynamic_002dcast"></a>Scheme Procedure: <strong>value-dynamic-cast</strong> <em>value type</em></dt>
|
||
|
|
<dd><p>Like <code>value-cast</code>, but works as if the C<tt>++</tt> <code>dynamic_cast</code>
|
||
|
|
operator were used. Consult a C<tt>++</tt> reference for details.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dreinterpret_002dcast"></a>Scheme Procedure: <strong>value-reinterpret-cast</strong> <em>value type</em></dt>
|
||
|
|
<dd><p>Like <code>value-cast</code>, but works as if the C<tt>++</tt> <code>reinterpret_cast</code>
|
||
|
|
operator were used. Consult a C<tt>++</tt> reference for details.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002ddereference"></a>Scheme Procedure: <strong>value-dereference</strong> <em>value</em></dt>
|
||
|
|
<dd><p>For pointer data types, this method returns a new <code><gdb:value></code> object
|
||
|
|
whose contents is the object pointed to by <var>value</var>. For example, if
|
||
|
|
<code>foo</code> is a C pointer to an <code>int</code>, declared in your C program as
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">int *foo;
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>then you can use the corresponding <code><gdb:value></code> to access what
|
||
|
|
<code>foo</code> points to like this:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define bar (value-dereference foo))
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The result <code>bar</code> will be a <code><gdb:value></code> object holding the
|
||
|
|
value pointed to by <code>foo</code>.
|
||
|
|
</p>
|
||
|
|
<p>A similar function <code>value-referenced-value</code> exists which also
|
||
|
|
returns <code><gdb:value></code> objects corresonding to the values pointed to
|
||
|
|
by pointer values (and additionally, values referenced by reference
|
||
|
|
values). However, the behavior of <code>value-dereference</code>
|
||
|
|
differs from <code>value-referenced-value</code> by the fact that the
|
||
|
|
behavior of <code>value-dereference</code> is identical to applying the C
|
||
|
|
unary operator <code>*</code> on a given value. For example, consider a
|
||
|
|
reference to a pointer <code>ptrref</code>, declared in your C<tt>++</tt> program
|
||
|
|
as
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">typedef int *intptr;
|
||
|
|
...
|
||
|
|
int val = 10;
|
||
|
|
intptr ptr = &val;
|
||
|
|
intptr &ptrref = ptr;
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Though <code>ptrref</code> is a reference value, one can apply the method
|
||
|
|
<code>value-dereference</code> to the <code><gdb:value></code> object corresponding
|
||
|
|
to it and obtain a <code><gdb:value></code> which is identical to that
|
||
|
|
corresponding to <code>val</code>. However, if you apply the method
|
||
|
|
<code>value-referenced-value</code>, the result would be a <code><gdb:value></code>
|
||
|
|
object identical to that corresponding to <code>ptr</code>.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define scm-ptrref (parse-and-eval "ptrref"))
|
||
|
|
(define scm-val (value-dereference scm-ptrref))
|
||
|
|
(define scm-ptr (value-referenced-value scm-ptrref))
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The <code><gdb:value></code> object <code>scm-val</code> is identical to that
|
||
|
|
corresponding to <code>val</code>, and <code>scm-ptr</code> is identical to that
|
||
|
|
corresponding to <code>ptr</code>. In general, <code>value-dereference</code> can
|
||
|
|
be applied whenever the C unary operator <code>*</code> can be applied
|
||
|
|
to the corresponding C value. For those cases where applying both
|
||
|
|
<code>value-dereference</code> and <code>value-referenced-value</code> is allowed,
|
||
|
|
the results obtained need not be identical (as we have seen in the above
|
||
|
|
example). The results are however identical when applied on
|
||
|
|
<code><gdb:value></code> objects corresponding to pointers (<code><gdb:value></code>
|
||
|
|
objects with type code <code>TYPE_CODE_PTR</code>) in a C/C<tt>++</tt> program.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dreferenced_002dvalue"></a>Scheme Procedure: <strong>value-referenced-value</strong> <em>value</em></dt>
|
||
|
|
<dd><p>For pointer or reference data types, this method returns a new
|
||
|
|
<code><gdb:value></code> object corresponding to the value referenced by the
|
||
|
|
pointer/reference value. For pointer data types,
|
||
|
|
<code>value-dereference</code> and <code>value-referenced-value</code> produce
|
||
|
|
identical results. The difference between these methods is that
|
||
|
|
<code>value-dereference</code> cannot get the values referenced by reference
|
||
|
|
values. For example, consider a reference to an <code>int</code>, declared
|
||
|
|
in your C<tt>++</tt> program as
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">int val = 10;
|
||
|
|
int &ref = val;
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>then applying <code>value-dereference</code> to the <code><gdb:value></code> object
|
||
|
|
corresponding to <code>ref</code> will result in an error, while applying
|
||
|
|
<code>value-referenced-value</code> will result in a <code><gdb:value></code> object
|
||
|
|
identical to that corresponding to <code>val</code>.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define scm-ref (parse-and-eval "ref"))
|
||
|
|
(define err-ref (value-dereference scm-ref)) ;; error
|
||
|
|
(define scm-val (value-referenced-value scm-ref)) ;; ok
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The <code><gdb:value></code> object <code>scm-val</code> is identical to that
|
||
|
|
corresponding to <code>val</code>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dfield"></a>Scheme Procedure: <strong>value-field</strong> <em>value field-name</em></dt>
|
||
|
|
<dd><p>Return field <var>field-name</var> from <code><gdb:value></code> object <var>value</var>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dsubscript"></a>Scheme Procedure: <strong>value-subscript</strong> <em>value index</em></dt>
|
||
|
|
<dd><p>Return the value of array <var>value</var> at index <var>index</var>.
|
||
|
|
The <var>value</var> argument must be a subscriptable <code><gdb:value></code> object.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dcall"></a>Scheme Procedure: <strong>value-call</strong> <em>value arg-list</em></dt>
|
||
|
|
<dd><p>Perform an inferior function call, taking <var>value</var> as a pointer
|
||
|
|
to the function to call.
|
||
|
|
Each element of list <var>arg-list</var> must be a <gdb:value> object or an object
|
||
|
|
that can be converted to a value.
|
||
|
|
The result is the value returned by the function.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003ebool"></a>Scheme Procedure: <strong>value->bool</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return the Scheme boolean representing <code><gdb:value></code> <var>value</var>.
|
||
|
|
The value must be “integer like”. Pointers are ok.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003einteger"></a>Scheme Procedure: <strong>value->integer</strong></dt>
|
||
|
|
<dd><p>Return the Scheme integer representing <code><gdb:value></code> <var>value</var>.
|
||
|
|
The value must be “integer like”. Pointers are ok.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003ereal"></a>Scheme Procedure: <strong>value->real</strong></dt>
|
||
|
|
<dd><p>Return the Scheme real number representing <code><gdb:value></code> <var>value</var>.
|
||
|
|
The value must be a number.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003ebytevector"></a>Scheme Procedure: <strong>value->bytevector</strong></dt>
|
||
|
|
<dd><p>Return a Scheme bytevector with the raw contents of <code><gdb:value></code>
|
||
|
|
<var>value</var>. No transformation, endian or otherwise, is performed.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003estring"></a>Scheme Procedure: <strong>value->string</strong> <em>value <span class="roman">[</span>#:encoding encoding<span class="roman">]</span> <span class="roman">[</span>#:errors errors<span class="roman">]</span> <span class="roman">[</span>#:length length<span class="roman">]</span></em></dt>
|
||
|
|
<dd><p>If <var>value></var> represents a string, then this method
|
||
|
|
converts the contents to a Guile string. Otherwise, this method will
|
||
|
|
throw an exception.
|
||
|
|
</p>
|
||
|
|
<p>Values are interpreted as strings according to the rules of the
|
||
|
|
current language. If the optional length argument is given, the
|
||
|
|
string will be converted to that length, and will include any embedded
|
||
|
|
zeroes that the string may contain. Otherwise, for languages
|
||
|
|
where the string is zero-terminated, the entire string will be
|
||
|
|
converted.
|
||
|
|
</p>
|
||
|
|
<p>For example, in C-like languages, a value is a string if it is a pointer
|
||
|
|
to or an array of characters or ints of type <code>wchar_t</code>, <code>char16_t</code>,
|
||
|
|
or <code>char32_t</code>.
|
||
|
|
</p>
|
||
|
|
<p>If the optional <var>encoding</var> argument is given, it must be a string
|
||
|
|
naming the encoding of the string in the <code><gdb:value></code>, such as
|
||
|
|
<code>"ascii"</code>, <code>"iso-8859-6"</code> or <code>"utf-8"</code>. It accepts
|
||
|
|
the same encodings as the corresponding argument to Guile’s
|
||
|
|
<code>scm_from_stringn</code> function, and the Guile codec machinery will be used
|
||
|
|
to convert the string. If <var>encoding</var> is not given, or if
|
||
|
|
<var>encoding</var> is the empty string, then either the <code>target-charset</code>
|
||
|
|
(see <a href="Character-Sets.html#Character-Sets">Character Sets</a>) will be used, or a language-specific encoding
|
||
|
|
will be used, if the current language is able to supply one.
|
||
|
|
</p>
|
||
|
|
<p>The optional <var>errors</var> argument is one of <code>#f</code>, <code>error</code> or
|
||
|
|
<code>substitute</code>. <code>error</code> and <code>substitute</code> must be symbols.
|
||
|
|
If <var>errors</var> is not specified, or if its value is <code>#f</code>, then the
|
||
|
|
default conversion strategy is used, which is set with the Scheme function
|
||
|
|
<code>set-port-conversion-strategy!</code>.
|
||
|
|
If the value is <code>'error</code> then an exception is thrown if there is any
|
||
|
|
conversion error. If the value is <code>'substitute</code> then any conversion
|
||
|
|
error is replaced with question marks.
|
||
|
|
See <a href="http://www.gnu.org/software/guile/manual/html_node/Strings.html#Strings">Strings</a> in <cite>GNU Guile Reference Manual</cite>.
|
||
|
|
</p>
|
||
|
|
<p>If the optional <var>length</var> argument is given, the string will be
|
||
|
|
fetched and converted to the given length.
|
||
|
|
The length must be a Scheme integer and not a <code><gdb:value></code> integer.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002d_003elazy_002dstring"></a>Scheme Procedure: <strong>value->lazy-string</strong> <em>value <span class="roman">[</span>#:encoding encoding<span class="roman">]</span> <span class="roman">[</span>#:length length<span class="roman">]</span></em></dt>
|
||
|
|
<dd><p>If this <code><gdb:value></code> represents a string, then this method
|
||
|
|
converts <var>value</var> to a <code><gdb:lazy-string</code> (see <a href="Lazy-Strings-In-Guile.html#Lazy-Strings-In-Guile">Lazy Strings In Guile</a>). Otherwise, this method will throw an exception.
|
||
|
|
</p>
|
||
|
|
<p>If the optional <var>encoding</var> argument is given, it must be a string
|
||
|
|
naming the encoding of the <code><gdb:lazy-string</code>. Some examples are:
|
||
|
|
<code>"ascii"</code>, <code>"iso-8859-6"</code> or <code>"utf-8"</code>. If the
|
||
|
|
<var>encoding</var> argument is an encoding that <small>GDB</small> does not
|
||
|
|
recognize, <small>GDB</small> will raise an error.
|
||
|
|
</p>
|
||
|
|
<p>When a lazy string is printed, the <small>GDB</small> encoding machinery is
|
||
|
|
used to convert the string during printing. If the optional
|
||
|
|
<var>encoding</var> argument is not provided, or is an empty string,
|
||
|
|
<small>GDB</small> will automatically select the encoding most suitable for
|
||
|
|
the string type. For further information on encoding in <small>GDB</small>
|
||
|
|
please see <a href="Character-Sets.html#Character-Sets">Character Sets</a>.
|
||
|
|
</p>
|
||
|
|
<p>If the optional <var>length</var> argument is given, the string will be
|
||
|
|
fetched and encoded to the length of characters specified. If
|
||
|
|
the <var>length</var> argument is not provided, the string will be fetched
|
||
|
|
and encoded until a null of appropriate width is found.
|
||
|
|
The length must be a Scheme integer and not a <code><gdb:value></code> integer.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dlazy_003f"></a>Scheme Procedure: <strong>value-lazy?</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return <code>#t</code> if <var>value</var> has not yet been fetched
|
||
|
|
from the inferior.
|
||
|
|
Otherwise return <code>#f</code>.
|
||
|
|
<small>GDB</small> does not fetch values until necessary, for efficiency.
|
||
|
|
For example:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define myval (parse-and-eval "somevar"))
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The value of <code>somevar</code> is not fetched at this time. It will be
|
||
|
|
fetched when the value is needed, or when the <code>fetch-lazy</code>
|
||
|
|
procedure is invoked.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-make_002dlazy_002dvalue"></a>Scheme Procedure: <strong>make-lazy-value</strong> <em>type address</em></dt>
|
||
|
|
<dd><p>Return a <code><gdb:value></code> that will be lazily fetched from the
|
||
|
|
target. The object of type <code><gdb:type></code> whose value to fetch is
|
||
|
|
specified by its <var>type</var> and its target memory <var>address</var>, which
|
||
|
|
is a Scheme integer.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dfetch_002dlazy_0021"></a>Scheme Procedure: <strong>value-fetch-lazy!</strong> <em>value</em></dt>
|
||
|
|
<dd><p>If <var>value</var> is a lazy value (<code>(value-lazy? value)</code> is <code>#t</code>),
|
||
|
|
then the value is fetched from the inferior.
|
||
|
|
Any errors that occur in the process will produce a Guile exception.
|
||
|
|
</p>
|
||
|
|
<p>If <var>value</var> is not a lazy value, this method has no effect.
|
||
|
|
</p>
|
||
|
|
<p>The result of this function is unspecified.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-value_002dprint"></a>Scheme Procedure: <strong>value-print</strong> <em>value</em></dt>
|
||
|
|
<dd><p>Return the string representation (print form) of <code><gdb:value></code>
|
||
|
|
<var>value</var>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Arithmetic-In-Guile.html#Arithmetic-In-Guile" accesskey="n" rel="next">Arithmetic In Guile</a>, Previous: <a href="Guile-Exception-Handling.html#Guile-Exception-Handling" accesskey="p" rel="prev">Guile Exception Handling</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>
|