dependent on the internal implementation details of the Lisp system.
@item
-The Lisp system can automatically convert objects back and forth
-between the Lisp and foreign representations. This is convenient, but
+The Lisp system can automatically convert objects back and forth between
+the Lisp and foreign representations. This is convenient, but
translation becomes prohibitively slow when large or complex data
structures must be shared. This approach is supported by the SBCL
-@acronym{FFI}, and used automatically by the when passing integers and
-strings.
+@acronym{FFI}, and used automatically when passing integers and strings.
@item
The Lisp program can directly manipulate foreign objects through the
@item
@cindex External formats
-The foreign type specifier @code{(sb-alien:c-string &key external-format
-element-type)} is similar to @code{(* char)}, but is interpreted as a
-null-terminated string, and is automatically converted into a Lisp
-string when accessed; or if the pointer is C @code{NULL} or @code{0},
-then accessing it gives Lisp @code{nil}.
+The foreign type specifier @code{(sb-alien:c-string &key
+external-format element-type not-null)} is similar to
+@code{(* char)}, but is interpreted as a null-terminated string, and
+is automatically converted into a Lisp string when accessed; or if the
+pointer is C @code{NULL} or @code{0}, then accessing it gives Lisp
+@code{nil} unless @code{not-null} is true, in which case a type-error
+is signalled.
External format conversion is automatically done when Lisp strings are
passed to foreign code, or when foreign strings are passed to Lisp code.
@item
@code{sb-alien} also exports translations of these C type
-specifiers as foreign type specifiers: @code{sb-alien:char},
-@code{sb-alien:short}, @code{sb-alien:int},
-@code{sb-alien:long}, @code{sb-alien:unsigned-char},
-@code{sb-alien:unsigned-short},
-@code{sb-alien:unsigned-int},
-@code{sb-alien:unsigned-long}, @code{sb-alien:float}, and
-@code{sb-alien:double}.
+specifiers as foreign type specifiers:
+@code{char},
+@code{short},
+@code{int},
+@code{long},
+@code{unsigned-char},
+@code{unsigned-short},
+@code{unsigned-int},
+@code{unsigned-long},
+@code{float}, @code{double},
+@code{size-t}, and @code{off-t}.
@end itemize
@subsection Foreign Dynamic Allocation
Lisp code can call the C standard library functions @code{malloc} and
-@code{free} to dynamically allocate and deallocate foreign
-variables. The Lisp code shares the same allocator with foreign C
-code, so it's OK for foreign code to call @code{free} on the result of
-Lisp @code{sb-alien:make-alien}, or for Lisp code to call
-@code{sb-alien:free-alien} on foreign objects allocated by C
-code.
-
-@defmac @sbalien{make-alien} @var{type} @var{size}
-
-The @code{sb-alien:make-alien} macro
-returns a dynamically allocated foreign value of the specified
-@var{type} (which is not evaluated.) The allocated memory is not
-initialized, and may contain arbitrary junk. If supplied,
-@var{size} is an expression to evaluate to compute the size of the
-allocated object. There are two major cases:
-
-@itemize
-@item
-When @var{type} is a foreign array type, an array of that type is
-allocated and a pointer to it is returned. Note that you must use
-@code{deref} to change the result to an array before you can use
-@code{deref} to read or write elements:
-
-@lisp
-(cl:in-package "CL-USER") ; which USEs package "SB-ALIEN"
-(defvar *foo* (make-alien (array char 10)))
-(type-of *foo*) @result{} (alien (* (array (signed 8) 10)))
-(setf (deref (deref foo) 0) 10) @result{} 10
-@end lisp
-
-If supplied, @var{size} is used as the first dimension for the
- array.
-
-@item
-When @var{type} is any other foreign type, then an object for that
-type is allocated, and a pointer to it is returned. So
-@code{(make-alien int)} returns a @code{(* int)}. If @var{size} is
-specified, then a block of that many objects is allocated, with the
-result pointing to the first one.
-
-@end itemize
-
-@end defmac
-
-@defun @sbalien{free-alien} @var{foreign-value}
-
-The @code{sb-alien:free-alien} macro
-frees the storage for @var{foreign-value},
-which must have been allocated with Lisp @code{make-alien}
-or C @code{malloc}.
-
-See also the @code{sb-alien:with-alien} macro, which allocates foreign
-values on the stack.
-@end defun
+@code{free} to dynamically allocate and deallocate foreign variables.
+The Lisp code shares the same allocator with foreign C code, so it's
+OK for foreign code to call @code{free} on the result of Lisp
+@code{sb-alien:make-alien}, or for Lisp code to call
+@code{sb-alien:free-alien} on foreign objects allocated by C code.
+
+@include macro-sb-alien-make-alien.texinfo
+@include fun-sb-alien-make-alien-string.texinfo
+@include fun-sb-alien-free-alien.texinfo
@node Foreign Variables
@comment node-name, next, previous, up
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