sha256/md5: leak: don't use borrowed buffer for hash.

It's incorrect to use a borrowed buf, because a borrowed buf
assumes that the memory isn't dynamically allocated, and will
not free it when it is finalized by the garbage collector.
The buffer which holds the hash returned by sha256 and md5
does in fact own the memory.

* buf.c (make_owned_buf): Static function becomes external.

* buf.h (make_owned_buf): Declared.

* chksum.c (chksum_ensure_buf): Use make_owned_buf rather than
make_borrowed_buf.

3 files changed, 3 insertions, 2 deletions

diff --git a/buf.c b/buf.c
index 4305952e..5d0fb268 100644
--- a/buf.c
+++ b/buf.c
@@ -130,7 +130,7 @@ val make_duplicate_buf(val len, mem_t *data)
   return obj;
 }
 
-static val make_owned_buf(val len, mem_t *data)
+val make_owned_buf(val len, mem_t *data)
 {
   val buf = make_borrowed_buf(len, data);
   buf->b.size = len;
diff --git a/buf.h b/buf.h
index 683d5438..1805f3b8 100644
--- a/buf.h
+++ b/buf.h
@@ -29,6 +29,7 @@ val make_buf(val len, val init_val, val alloc_size);
 val bufp(val object);
 val make_borrowed_buf(val len, mem_t *data);
 val init_borrowed_buf(obj_t *buf, val len, mem_t *data);
+val make_owned_buf(val len, mem_t *data);
 val make_duplicate_buf(val len, mem_t *data);
 val copy_buf(val buf);
 val buf_trim(val buf);
diff --git a/chksum.c b/chksum.c
index ad12d7d4..215d4f57 100644
--- a/chksum.c
+++ b/chksum.c
@@ -97,7 +97,7 @@ static val chksum_ensure_buf(val self, val buf_in,
 {
   if (null_or_missing_p(buf_in)) {
     *phash = chk_malloc(c_unum(len, self));
-    return make_borrowed_buf(len, *phash);
+    return make_owned_buf(len, *phash);
   } else {
     *phash = buf_get(buf_in, self);
     if (lt(length_buf(buf_in), len))