ffi: allow nil object to convert under closure type.

* ffi.c (ffi_closure_put): Only diagnose a bad object if it's
not nil, otherwise let the null value of p through.
This is useful because there are sometimes C interfaces which
take an optional function pointer, whereby a null value
indicates that the pointer is not specified.

1 files changed, 1 insertions, 1 deletions

diff --git a/ffi.c b/ffi.c
index 25d8a8d5..7c001187 100644
--- a/ffi.c
+++ b/ffi.c
@@ -2142,7 +2142,7 @@ static void ffi_closure_put(struct txr_ffi_type *tft, val ptr, mem_t *dst,
   } else if (type == ffi_closure_s) {
     struct txr_ffi_closure *tfcl = ffi_closure_struct(ptr);
     p = tfcl->fptr;
-  } else {
+  } else if (ptr != nil) {
     uw_throwf(error_s, lit("~a: ~s cannot be used as function pointer"),
               self, ptr, nao);
   }