diff options
| -rw-r--r-- | share/txr/stdlib/ffi.tl | 18 | ||||
| -rw-r--r-- | txr.1 | 59 |
2 files changed, 69 insertions, 8 deletions
diff --git a/share/txr/stdlib/ffi.tl b/share/txr/stdlib/ffi.tl index e171cb47..480faf5d 100644 --- a/share/txr/stdlib/ffi.tl +++ b/share/txr/stdlib/ffi.tl @@ -54,12 +54,18 @@ (t exp))) (defun sys:analyze-argtypes (form argtypes) - (let ((p (posq : argtypes))) - (when p - (if (zerop p) - (compile-error form "variadic with zero fixed arguments not allowed") - (del [argtypes p]))) - (list* (length argtypes) p argtypes))) + (tree-bind (: ftypes vtypes) (split* argtypes (op where (op eq :))) + (when vtypes + (when (null ftypes) + (compile-error form "variadic with zero fixed arguments not allowed")) + (set vtypes + (collect-each ((vt vtypes)) + (caseq vt + ((float) 'double) + ((be-float le-float) + (compile-error form "variadic argument cannot be of type ~s" + vt)))))) + (list* (+ (len ftypes) (len vtypes)) (len ftypes) (append ftypes vtypes)))) (defmacro deffi (:form f :env e name fun-expr rettype argtypes) @@ -72113,6 +72113,26 @@ descriptor, and even if the return types and argument types match. +Note: unlike the +.code deffi +and +.code deffi-cb +macros, +the +.code ffi-make-call-desc +function doesn't perform any special treatment of variadic parameter types. +When any of the types +.codn float , +.code be-float +or +.code le-float +occur in the variadic portion of +.metn argtypes , +it is unspecified whether a descriptor is successfully produced and returned +or whether an exception is thrown. If a descriptor is successfully produced, +and then subsequently used for making or accepting calls, the behavior is +undefined. + .TP* Example: .verb @@ -72689,8 +72709,9 @@ symbol appears as one of the elements of then the .code deffi form specifies a fixed call to a foreign function which is variadic. The -argument types before the colon keyword are the fixed arguments. The types -after the colon, if any, are the variadic arguments. +argument types before the colon keyword are the types of the fixed arguments. +The types after the colon, if any, are of the variadic arguments. Special +considerations apply to some variadic argument types, described below. The following syntactic variants are permitted of the .meta fun-expr @@ -72732,6 +72753,40 @@ macro. .RE .IP +When the FFI type +.code float +is used as the type of a variadic parameter, +.code deffi +replaces it by the FFI type +.codn double . +This treatment is necessary because the C variadic argument mechanism promotes +.code float +values to +.codn double . +Note: due to this substitution, it is possible to pass floating-point values +which are out of range of the +.code float +type, without any diagnosis. The behavior of is undefined in the +Lisp-to-C direction, if the C function extracts an out-of-range +.code double +argument as if it were of type +.codn float . + +The FFI types +.code be-float +and +.code le-float +cannot be used for specifying the types of a variadic argument. If any of +these occur in that position, +.code deffi +throws an error. +Rationale: these types are related to the C type +.code float +type, which requires promotion in variadic passing. Promotion cannot +be performed on floating-point values whose byte order has been rearranged, +because promotion is a value-preserving conversion. + +.IP The result value of a .code deffi form is |