diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 33 |
1 files changed, 30 insertions, 3 deletions
@@ -73233,11 +73233,29 @@ the foreign function alters the pointer. .coNP FFI type @ closure The .code closure -type converts two kinds of Lisp objects to a C pointer: the +type converts three kinds of Lisp objects to a C pointer: the object +.codn nil , +the .code cptr -type, and the special +type, or the special .code ffi-closure -type, whose instances are produced by the +type. + +When the +.code nil +symbol is converted to a +.code closure +type, it becomes a null function pointer. + +A +.code cptr +object of any kind converts to a +.codn closure ; +the internal pointer is converted to a function pointer. + +Instances of the +.code ffi-closure +type are produced by the .code ffi-make-closure function, or by calls to functions defined by the .code deffi-cb @@ -73246,6 +73264,15 @@ macro. The type is useful for passing callbacks to foreign functions: Lisp functions which appear to be C functions to foreign code. +In the reverse direction, when a +.code closure +object is converted from the foreign function pointer representation +to a Lisp object, it becomes a +.code cptr +object whose tag is the +.code closure +symbol. + .coNP FFI type @ void The .code void |