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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 18 |
1 files changed, 18 insertions, 0 deletions
@@ -53374,6 +53374,24 @@ only \*(TL .code float type. +.ccIP @ val +The FFI +.code val +type denotes the machine representation of a Lisp value cell, which is +corresponds to a C pointer. Not all cell values are actually pointers, but +values that are heap objects, such as vectors and conses, are. +The +.code val +type transparently converts any Lisp object to a foreign pointer value +with no representation change at all; and performs the reverse conversion +from pointer to Lisp value. + +Note: this is utterly dangerous. Lisp values that aren't pointers must not +be dereferenced by foreign code. Foreign code must not generate Lisp pointer +values that aren't objects which came from a Lisp heap. +Interpreting a Lisp value in foreign code requires a correct decoding of +its type tag, and, if necessary, stripping the tag bits to recover a heap +pointer and interpreting the type code stored in the heap object. .ccIP @ cptr This type corresponds to a C pointer of any type, including a function pointer; \*(TX doesn't run on any exotic platforms in which there is a representational |