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+<?xml version='1.0' ?> <!-- Mode: Docbook -->
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "file:///usr/share/sgml/docbook/dtd/xml/4.2/docbookx.dtd" [
+<!ENTITY % myents SYSTEM "entities.xml">
+%myents;
+]>
+
+<reference id="objects">
+ <title>Objects</title>
+<partintro>
+<title>Overview</title>
+ <para>
+ Objects are entities that can allocated, referred to by pointers, and
+can be freed.
+ </para>
+</partintro>
+
+
+ <refentry id="allocate-foreign-object">
+ <refnamediv>
+ <refname>allocate-foreign-object</refname>
+ <refpurpose>Allocates an instance of a foreign object.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>allocate-foreign-object</function> <replaceable>type &optional size</replaceable> => <returnvalue>ptr</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>The type of foreign object to allocate. This parameter is evaluated.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>size</parameter></term>
+ <listitem>
+ <para>An optional size parameter that is evaluated. If specified, allocates and returns an
+array of <parameter>type</parameter> that is <parameter>size</parameter> members long. This parameter is evaluated.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>ptr</returnvalue></term>
+ <listitem>
+ <para>A pointer to the foreign object.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Allocates an instance of a foreign object. It returns a pointer to the object.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <programlisting>
+(def-struct ab (a :int) (b :double))
+(allocate-foreign-object 'ab)
+=> #<ptr>
+ </programlisting>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+
+ <refentry id="free-foreign-object">
+ <refnamediv>
+ <refname>free-foreign-object</refname>
+ <refpurpose>Frees memory that was allocated for a foreign boject.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>free-foreign-object</function> <replaceable>ptr</replaceable>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>A pointer to the allocated foreign object to free.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Frees the memory used by the allocation of a foreign object.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+
+ <refentry id="with-foreign-object">
+ <refnamediv>
+ <refname>with-foreign-object</refname>
+ <refpurpose>Wraps the allocation of a foreign object around a body of code.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>with-foreign-object</function> <replaceable>(var type) &body body</replaceable> => <returnvalue>form-return</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>var</parameter></term>
+ <listitem>
+ <para>The variable name to bind.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>The type of foreign object to allocate. This parameter is evaluated.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>form-return</returnvalue></term>
+ <listitem>
+ <para>The result of evaluating the <parameter>body</parameter>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+This function wraps the allocation, binding, and destruction of a foreign object.
+On &cmucl; and
+&lw; platforms the object is stack allocated for efficiency. Benchmarks show that &acl; performs
+much better with static allocation.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <programlisting>
+(defun gethostname2 ()
+ "Returns the hostname"
+ (uffi:with-foreign-object (name '(:array :unsigned-char 256))
+ (if (zerop (c-gethostname (uffi:char-array-to-pointer name) 256))
+ (uffi:convert-from-foreign-string name)
+ (error "gethostname() failed."))))
+ </programlisting>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="size-of-foreign-type">
+ <refnamediv>
+ <refname>size-of-foreign-type</refname>
+ <refpurpose>Returns the number of data bytes used by a foreign object type.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>size-of-foreign-type</function> <replaceable>ftype</replaceable>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ftype</parameter></term>
+ <listitem>
+ <para>A foreign type specifier. This parameter is evaluated.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Returns the number of data bytes used by a foreign object type. This does not include any Lisp storage overhead.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <para>
+<programlisting>
+(size-of-foreign-object :unsigned-byte)
+=> 1
+(size-of-foreign-object 'my-100-byte-vector-type)
+=> 100
+</programlisting>
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1> <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="pointer-address">
+ <refnamediv>
+ <refname>pointer-address</refname>
+ <refpurpose>Returns the address of a pointer.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>pointer-address</function> <replaceable>ptr</replaceable> => <returnvalue>address</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>A pointer to a foreign object.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>address</parameter></term>
+ <listitem>
+ <para>An integer representing the pointer's address.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Returns the address as an integer of a pointer.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+
+ <refentry id="deref-pointer">
+ <refnamediv>
+ <refname>deref-pointer</refname>
+ <refpurpose>Deferences a pointer.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>deref-pointer</function> <replaceable>ptr type</replaceable> => <returnvalue>value</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>A pointer to a foreign object.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>A foreign type of the object being pointed to.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>value</returnvalue></term>
+ <listitem>
+ <para>The value of the object where the pointer points.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Returns the object to which a pointer points.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <para>
+<programlisting>
+(let ((intp (allocate-foreign-object :int)))
+ (setf (deref-pointer intp :int) 10)
+ (prog1
+ (deref-pointer intp :int)
+ (free-foreign-object intp)))
+=> 10
+</programlisting>
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Notes</title>
+ <para>
+ The TYPE argument is ignored for CL implementations other than
+ AllegroCL. If you want to cast a pointer to another type use
+ WITH-CAST-POINTER together with DEREF-POINTER/DEREF-ARRAY.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="ensure-char-character">
+ <refnamediv>
+ <refname>ensure-char-character</refname>
+ <refpurpose>Ensures that a dereferenced <constant>:char</constant> pointer is
+a character.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>ensure-char-character</function> <replaceable>object</replaceable> => <returnvalue>char</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>object</parameter></term>
+ <listitem>
+ <para>Either a character or a integer specifying a character code.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>char</returnvalue></term>
+ <listitem>
+ <para>A character.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Ensures that an objects obtained by dereferencing
+<constant>:char</constant> and <constant>:unsigned-char</constant>
+pointers are a lisp character.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <para>
+<programlisting>
+(let ((fs (convert-to-foreign-string "a")))
+ (prog1
+ (ensure-char-character (deref-pointer fs :char))
+ (free-foreign-object fs)))
+=> #\a
+</programlisting>
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>Depending upon the implementation and what &uffi; expects, this
+macro may signal an error if the object is not a character or
+integer.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="ensure-char-integer">
+ <refnamediv>
+ <refname>ensure-char-integer</refname>
+ <refpurpose>Ensures that a dereferenced <constant>:char</constant> pointer is
+an integer.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>ensure-char-integer</function> <replaceable>object</replaceable> => <returnvalue>int</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>object</parameter></term>
+ <listitem>
+ <para>Either a character or a integer specifying a character code.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>int</returnvalue></term>
+ <listitem>
+ <para>An integer.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Ensures that an object obtained by dereferencing a
+<constant>:char</constant> pointer is an integer.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <para>
+<programlisting>
+(let ((fs (convert-to-foreign-string "a")))
+ (prog1
+ (ensure-char-integer (deref-pointer fs :char))
+ (free-foreign-object fs)))
+=> 96
+</programlisting>
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>Depending upon the implementation and what &uffi; expects, this
+macro may signal an error if the object is not a character or
+integer.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="make-null-pointer">
+ <refnamediv>
+ <refname>make-null-pointer</refname>
+ <refpurpose>Create a &null; pointer.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>make-null-pointer</function> <replaceable>type</replaceable> => <returnvalue>ptr</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>A type of object to which the pointer refers.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>The &null; pointer of type <parameter>type</parameter>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Creates a &null; pointer of a specified type.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+
+ <refentry id="null-pointer-p">
+ <refnamediv>
+ <refname>null-pointer-p</refname>
+ <refpurpose>Tests a pointer for &null; value.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>null-pointer-p</function> <replaceable>ptr</replaceable> => <returnvalue>is-null</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>A foreign object pointer.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>is-null</returnvalue></term>
+ <listitem>
+ <para>The boolean flag.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ A predicate testing if a pointer is has a &null; value.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+
+ <refentry id="null-cstring-pointer">
+ <refnamediv>
+ <refname>+null-cstring-pointer+</refname>
+ <refpurpose>A constant &null; cstring pointer.
+ </refpurpose>
+ <refclass>Constant</refclass>
+ </refnamediv>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ A &null; cstring pointer. This can be used for testing
+if a cstring returned by a function is &null;.
+ </para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="with-cast-pointer">
+ <refnamediv>
+ <refname>with-cast-pointer</refname>
+ <refpurpose>Wraps a body of code with a pointer cast to a new type.
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>with-cast-pointer</function> (<replaceable>binding-name ptr type) & body body</replaceable> => <returnvalue>value</returnvalue>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>ptr</parameter></term>
+ <listitem>
+ <para>A pointer to a foreign object.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>A foreign type of the object being pointed to.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>value</returnvalue></term>
+ <listitem>
+ <para>The value of the object where the pointer points.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+ Executes BODY with POINTER cast to be a pointer to type TYPE. If
+ BINDING-NAME is provided the cast pointer will be bound to this
+ name during the execution of BODY. If BINDING-NAME is not provided
+ POINTER must be a name bound to the pointer which should be
+ cast. This name will be bound to the cast pointer during the
+ execution of BODY.
+
+ This is a no-op in AllegroCL but will wrap BODY in a LET form if
+ BINDING-NAME is provided.
+
+ This macro is meant to be used in conjunction with DEREF-POINTER or
+ DEREF-ARRAY. In Allegro CL the "cast" will actually take place in
+ DEREF-POINTER or DEREF-ARRAY.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+<programlisting>
+(with-foreign-object (size :int)
+ ;; FOO is a foreign function returning a :POINTER-VOID
+ (let ((memory (foo size)))
+ (when (mumble)
+ ;; at this point we know for some reason that MEMORY points
+ ;; to an array of unsigned bytes
+ (with-cast-pointer (memory :unsigned-byte)
+ (dotimes (i (deref-pointer size :int))
+ (do-something-with
+ (deref-array memory '(:array :unsigned-byte) i)))))))
+</programlisting>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+ <refentry id="def-foreign-var">
+ <refnamediv>
+ <refname>def-foreign-var</refname>
+ <refpurpose>
+Defines a symbol macro to access a variable in foreign code
+ </refpurpose>
+ <refclass>Macro</refclass>
+ </refnamediv>
+ <refsynopsisdiv>
+ <title>Syntax</title>
+ <synopsis>
+ <function>def-foreign-var</function> <replaceable>name type module</replaceable>
+ </synopsis>
+ </refsynopsisdiv>
+ <refsect1>
+ <title>Arguments and Values</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>name</parameter></term>
+ <listitem>
+ <para>
+A string or list specificying the symbol macro's name. If it is a
+ string, that names the foreign variable. A Lisp name is created
+ by translating #\_ to #\- and by converting to upper-case in
+ case-insensitive Lisp implementations. If it is a list, the first
+ item is a string specifying the foreign variable name and the
+ second it is a symbol stating the Lisp name.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>type</parameter></term>
+ <listitem>
+ <para>A foreign type of the foreign variable.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><returnvalue>module</returnvalue></term>
+ <listitem>
+ <para>
+ A string specifying the module (or library) the foreign variable
+ resides in. (Required by Lispworks)
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1>
+ <title>Description</title>
+ <para>
+Defines a symbol macro which can be used to access (get and set) the
+value of a variable in foreign code.
+ </para>
+ </refsect1>
+ <refsect1>
+ <title>Examples</title>
+ <refsect2>
+ <title>C code</title>
+<programlisting>
+ int baz = 3;
+
+ typedef struct {
+ int x;
+ double y;
+ } foo_struct;
+
+ foo_struct the_struct = { 42, 3.2 };
+
+ int foo () {
+ return baz;
+ }
+</programlisting>
+</refsect2>
+<refsect2>
+<title>Lisp code</title>
+<programlisting>
+ (uffi:def-struct foo-struct
+ (x :int)
+ (y :double))
+
+ (uffi:def-function ("foo" foo)
+ ()
+ :returning :int
+ :module "foo")
+
+ (uffi:def-foreign-var ("baz" *baz*) :int "foo")
+ (uffi:def-foreign-var ("the_struct" *the-struct*) foo-struct "foo")
+
+
+*baz*
+ => 3
+
+(incf *baz*)
+ => 4
+
+(foo)
+ => 4
+</programlisting>
+</refsect2>
+ </refsect1>
+ <refsect1>
+ <title>Side Effects</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Affected by</title>
+ <para>None.</para>
+ </refsect1>
+ <refsect1>
+ <title>Exceptional Situations</title>
+ <para>None.</para>
+ </refsect1>
+ </refentry>
+
+</reference>