ffi: alignment bug in undimensioned arrays.

Because the varray behavior for undimensioned arrays was introduced
in dubious commit 7880c9b565ab438e1bf0250a967acdbf8d04cb42
in 2017, which used make_ffi_type_pointer to register the type,
claiming that the C representation is pointer (which was not true
in that commit, nor ever since).
As a result, though, undimensioned arrays received the alignment
of pointers, rather than deriving it from the element type.
Thus (array char) has 4 or 8 byte alignment whereas (array 4 char)
correctly has 1 byte alignment.

* ffi.c (ffi_type_compile): Use make_ffi_type_array for the two-element
array syntax, just like for the dimensioned case with three elements.
Then override some of the functions with the varray versions.

* tests/017/ffi-misc.tl: Fix the test case which exposed this.
In the type (struct flex (a char) (b (zarray char)), the array
b must be at offset 1. I didn't notice that the offset of 4
being confirmed by the test case was wrong, but this showed up
when running the test case on a platform with 8 byte pointers.

1 files changed, 8 insertions, 6 deletions

diff --git a/ffi.c b/ffi.c
index c8c8ca82..53ccffb7 100644
--- a/ffi.c
+++ b/ffi.c
@@ -3820,15 +3820,10 @@ val ffi_type_compile(val syntax)
       if (length(syntax) == two) {
         val eltype_syntax = cadr(syntax);
         val eltype = ffi_type_compile(eltype_syntax);
-        val type = make_ffi_type_pointer(syntax, vec_s,
-                                         ffi_varray_put, ffi_void_get,
-                                         ffi_varray_in, 0, ffi_varray_release,
-                                         eltype);
+        val type = make_ffi_type_array(syntax, vec_s, zero, eltype, self);
         struct txr_ffi_type *tft = ffi_type_struct(type);
         struct txr_ffi_type *etft = ffi_type_struct(eltype);
 
-        tft->kind = FFI_KIND_ARRAY;
-
         if (etft->incomplete || etft->bitfield)
           uw_throwf(error_s,
                     lit("~a: ~a ~s cannot be array element"),
@@ -3836,6 +3831,13 @@ val ffi_type_compile(val syntax)
                     if3(etft->bitfield,
                         lit("bitfield"), lit("incomplete type")),
                     eltype_syntax, nao);
+
+        tft->put = ffi_varray_put;
+        tft->get = ffi_void_get;
+        tft->in = ffi_varray_in;
+        tft->out = 0;
+        tft->release = ffi_varray_release;
+
         if (sym == zarray_s) {
           tft->null_term = 1;
           tft->get = ffi_varray_null_term_get;