ffi: bugfix: broken buf in semantics, bad doc.

* ffi.c (ffi_buf_in): The bug in this one is that if *loc
has been mutated to a null pointer, we want to produce
a nil, rather than to try to duplicate the buffer.
(ffi_buf_d_in): The bug here is that *loc is always
different from origptr, because origptr is from the original
buffer object, whereas we placed a copy of it into *loc.
The semantics is changed. We take ownership of whatever
pointer is there. If it is null, then yield nil.

* txr.1: buf and buf-d documentation revised.

1 files changed, 4 insertions, 9 deletions

diff --git a/ffi.c b/ffi.c
index b2ce6441..693c700f 100644
--- a/ffi.c
+++ b/ffi.c
@@ -706,7 +706,7 @@ static val ffi_buf_in(struct txr_ffi_type *tft, int copy, mem_t *src,
   mem_t *origptr = buf_get(obj, self);
 
   if (copy && *loc != origptr)
-    obj = make_duplicate_buf(length_buf(obj), *loc);
+    obj = if2(*loc, make_duplicate_buf(length_buf(obj), *loc));
 
   return obj;
 }
@@ -732,15 +732,10 @@ static val ffi_buf_d_in(struct txr_ffi_type *tft, int copy, mem_t *src,
                         val obj, val self)
 {
   mem_t **loc = coerce(mem_t **, src);
-  mem_t *origptr = buf_get(obj, self);
 
-  if (*loc != origptr) {
-    if (copy) {
-      obj = make_borrowed_buf(length_buf(obj), *loc);
-    } else {
-      free(*loc);
-      *loc = 0;
-    }
+  if (copy) {
+    obj = if2(*loc, make_borrowed_buf(length_buf(obj), *loc));
+    *loc = 0;
   }
 
   return obj;