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-rw-r--r--erts/doc/src/erl_nif.xml33
1 files changed, 28 insertions, 5 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 5a69bed34c..50e07f019e 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -206,7 +206,7 @@ ok
<seealso marker="#enif_make_resource">
<c>enif_make_resource</c></seealso>.
The term returned by <c>enif_make_resource</c> is opaque in nature.
- It can be stored and passed between processes on the same node, but
+ It can be stored and passed between processes, but
the only real end usage is to pass it back as an argument to a NIF.
The NIF can then call <seealso marker="#enif_get_resource">
<c>enif_get_resource</c></seealso> and get back a pointer to the
@@ -1952,10 +1952,33 @@ typedef enum {
details, see the <seealso marker="#enif_resource_example">example of
creating and returning a resource object</seealso> in the User's
Guide.</p>
- <p>Notice that the only defined behavior of using a resource term in
- an Erlang program is to store it and send it between processes on the
- same node. Other operations, such as matching or
- <c>term_to_binary</c>, have unpredictable (but harmless) results.</p>
+ <note>
+ <p>Since ERTS 9.0 (OTP-20.0), resource terms have a defined behavior
+ when compared and serialized through <c>term_to_binary</c> or passed
+ between nodes.</p>
+ <list type="bulleted">
+ <item>
+ <p>Two resource terms will compare equal iff they
+ would yield the same resource object pointer when passed to
+ <seealso marker="#enif_get_resource"><c>enif_get_resource</c></seealso>.</p>
+ </item>
+ <item>
+ <p>A resoure term can be serialized with <c>term_to_binary</c> and later
+ be fully recreated if the resource object is still alive when
+ <c>binary_to_term</c> is called. A <em>stale</em> resource term will be
+ returned from <c>binary_to_term</c> if the resource object has
+ been deallocated. <seealso marker="#enif_get_resource"><c>enif_get_resource</c></seealso>
+ will return false for stale resource terms.</p>
+ <p>The same principles of serialization apply when passing
+ resource terms in messages to remote nodes and back again. A
+ resource term will act stale on all nodes except the node where
+ its resource object is still alive in memory.</p>
+ </item>
+ </list>
+ <p>Before ERTS 9.0 (OTP-20.0), all resource terms did
+ compare equal to each other and to empty binaries (<c>&lt;&lt;&gt;&gt;</c>).
+ If serialized, they would be recreated as plain empty binaries.</p>
+ </note>
</desc>
</func>