ffi: bufix: elide get if copy flag is false.

* ffi.c (ffi_struct_in, ffi_array_in): Only fall back on get
if the copy flag is true. If the copy flag is false, we must
not extract. That's not ony as an optimization (no point in
extracting back from by-value objects).  We also avoid
extracting from pointers we don't own, like in the case
of str-d, where the pointer is owned by the foreign function
and may have been freed.

1 files changed, 2 insertions, 2 deletions

diff --git a/ffi.c b/ffi.c
index 1a9ebb01..6d41bcff 100644
--- a/ffi.c
+++ b/ffi.c
@@ -862,7 +862,7 @@ static val ffi_struct_in(struct txr_ffi_type *tft, int copy, mem_t *src,
       if (mtft->in != 0) {
         val slval = slot(strct, slsym);
         slotset(strct, slsym, mtft->in(mtft, copy, src + offs, slval, self));
-      } else {
+      } else if (copy) {
         val slval = mtft->get(mtft, src + offs, self);
         slotset(strct, slsym, slval);
       }
@@ -1013,7 +1013,7 @@ static val ffi_array_in(struct txr_ffi_type *tft, int copy, mem_t *src,
       if (etft->in != 0) {
         val elval = ref(vec, num_fast(i));
         refset(vec, num_fast(i), etft->in(etft, copy, src + offs, elval, self));
-      } else {
+      } else if (copy) {
         val elval = etft->get(etft, src + offs, self);
         refset(vec, num_fast(i), elval);
       }