ffi: bugfix: empty structs/unions have alignment of 1.

* ffi.c (make_ffi_type_struct, make_ffi_type_union): Initialize
most_align local variable to 1, so the lower bound of alignment
is that, rather than zero.

* tests/017/ffi-misc.tl: Tests added.

1 files changed, 2 insertions, 2 deletions

diff --git a/ffi.c b/ffi.c
index 1e60e95b..79d59a8b 100644
--- a/ffi.c
+++ b/ffi.c
@@ -3461,7 +3461,7 @@ static val make_ffi_type_struct(val syntax, val lisp_type,
                 tft->self,
                 cobj(coerce(mem_t *, tft), ffi_type_cls, &ffi_type_struct_ops));
   ucnum offs = 0;
-  ucnum most_align = 0;
+  ucnum most_align = 1;
   int need_out_handler = 0;
   int bit_offs = 0;
   const unsigned bits_int = 8 * sizeof(int);
@@ -3642,7 +3642,7 @@ static val make_ffi_type_union(val syntax, val use_existing, val self)
   val obj = if3(use_existing,
                 tft->self,
                 cobj(coerce(mem_t *, tft), ffi_type_cls, &ffi_type_struct_ops));
-  ucnum most_align = 0;
+  ucnum most_align = 1;
   ucnum biggest_size = 0;
   const unsigned bits_int = 8 * sizeof(int);
 #if HAVE_I64