From 5a23c7cf3c5eccac6e6de775722bc1136a66be83 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Mon, 5 Jul 2021 17:54:45 +0100
Subject: [PATCH] ocaml: Call caml_shutdown when unloading the plugin

This has several useful effects (taken from the OCaml documentation):

* Running the functions that were registered with "Stdlib.at_exit".

* Triggering finalization of allocated custom blocks.  For example,
  "Stdlib.in_channel" and "Stdlib.out_channel" are represented by
  custom blocks that enclose file descriptors, which are to be
  released.

* Unloading the dependent shared libraries that were loaded by the runtime,
  including "dynlink" plugins.

* Freeing the memory blocks that were allocated by the runtime with
  "malloc".

If the function is not present (for OCaml < 4.05) then we just skip
this step.

(cherry picked from commit 99140272a0675b3d123d2c42cb0a5ab73b09fba2)
---
 configure.ac           | 18 ++++++++++++++++++
 plugins/ocaml/plugin.c |  4 ++++
 2 files changed, 22 insertions(+)

diff --git a/configure.ac b/configure.ac
index 9b171b7e..a7c4c8d3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -857,6 +857,24 @@ EOF
     rm -f conftest.c conftest.o
 ])
 
+dnl Check if OCaml has caml_shutdown (added 2014).
+AS_IF([test "x$OCAMLC" != "xno" && test "x$OCAMLFIND" != "xno" && \
+       test "x$enable_ocaml" = "xyes"],[
+    AC_MSG_CHECKING([for caml_shutdown])
+    cat >conftest.c <<'EOF'
+#include <caml/callback.h>
+int main () { char *p = (void *) caml_shutdown; return 0; }
+EOF
+    AS_IF([$OCAMLC conftest.c >&AS_MESSAGE_LOG_FD 2>&1],[
+        AC_MSG_RESULT([yes])
+        AC_DEFINE([HAVE_CAML_SHUTDOWN],[1],
+                  [caml_shutdown found at compile time.])
+    ],[
+        AC_MSG_RESULT([no])
+    ])
+    rm -f conftest.c conftest.o
+])
+
 dnl For developing plugins in Rust, optional.
 AC_CHECK_PROG([CARGO],[cargo],[cargo],[no])
 AC_ARG_ENABLE([rust],
diff --git a/plugins/ocaml/plugin.c b/plugins/ocaml/plugin.c
index 00959cb6..9d7d72ad 100644
--- a/plugins/ocaml/plugin.c
+++ b/plugins/ocaml/plugin.c
@@ -131,6 +131,10 @@ unload_wrapper (void)
   free ((char *) plugin.config_help);
 
   remove_roots ();
+
+#ifdef HAVE_CAML_SHUTDOWN
+  caml_shutdown ();
+#endif
 }
 
 static void
-- 
2.31.1