[Tarantool-patches] [PATCH v19 6/6] test: box/cfunc -- add cmod test

[Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Note that the test is disabled in suite.ini for a while
because we need to update test-run first like

 | diff --git a/pretest_clean.lua b/pretest_clean.lua
 | index 9b5ac9d..b0280c4 100644
 | --- a/pretest_clean.lua
 | +++ b/pretest_clean.lua
 | @@ -272,6 +272,7 @@ local function clean()
 |          package = true,
 |          pickle = true,
 |          popen = true,
 | +        cmod = true,
 |          pwd = true,
 |          socket = true,
 |          strict = true,

Part-of #4642

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 test/box/CMakeLists.txt |   4 +
 test/box/cfunc1.c       |  58 +++++
 test/box/cfunc2.c       | 137 +++++++++++
 test/box/cfunc3.c       |  25 ++
 test/box/cfunc4.c       |  28 +++
 test/box/cmod.result    | 530 ++++++++++++++++++++++++++++++++++++++++
 test/box/cmod.test.lua  | 203 +++++++++++++++
 test/box/suite.ini      |   2 +-
 8 files changed, 986 insertions(+), 1 deletion(-)
 create mode 100644 test/box/cfunc1.c
 create mode 100644 test/box/cfunc2.c
 create mode 100644 test/box/cfunc3.c
 create mode 100644 test/box/cfunc4.c
 create mode 100644 test/box/cmod.result
 create mode 100644 test/box/cmod.test.lua

diff --git a/test/box/CMakeLists.txt b/test/box/CMakeLists.txt
index 06bfbbe9d..939353981 100644
--- a/test/box/CMakeLists.txt
+++ b/test/box/CMakeLists.txt
@@ -3,3 +3,7 @@ build_module(function1 function1.c)
 build_module(reload1 reload1.c)
 build_module(reload2 reload2.c)
 build_module(tuple_bench tuple_bench.c)
+build_module(cfunc1 cfunc1.c)
+build_module(cfunc2 cfunc2.c)
+build_module(cfunc3 cfunc3.c)
+build_module(cfunc4 cfunc4.c)
diff --git a/test/box/cfunc1.c b/test/box/cfunc1.c
new file mode 100644
index 000000000..f6829372a
--- /dev/null
+++ b/test/box/cfunc1.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <msgpuck.h>
+
+#include "module.h"
+
+/*
+ * Before the reload functions are just declared
+ * and simply exit with zero.
+ *
+ * After the module reload we should provide real
+ * functionality.
+ */
+
+int
+cfunc_nop(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
+
+int
+cfunc_fetch_seq_evens(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
+
+int
+cfunc_multireturn(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
+
+int
+cfunc_args(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
+
+int
+cfunc_sum(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
diff --git a/test/box/cfunc2.c b/test/box/cfunc2.c
new file mode 100644
index 000000000..8c583e993
--- /dev/null
+++ b/test/box/cfunc2.c
@@ -0,0 +1,137 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <msgpuck.h>
+
+#include "module.h"
+
+/*
+ * Just make sure we've been called.
+ */
+int
+cfunc_nop(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	(void)ctx;
+	(void)args;
+	(void)args_end;
+	return 0;
+}
+
+/*
+ * Fetch first N even numbers (just to make sure the order of
+ * arguments is not screwed).
+ */
+int
+cfunc_fetch_seq_evens(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	int arg_count = mp_decode_array(&args);
+	if (arg_count != 1) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid argument count");
+	}
+	int field_count = mp_decode_array(&args);
+	if (field_count < 1) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid array size");
+	}
+
+	/*
+	 * We expect even numbers sequence here. The idea is
+	 * to test invalid data an issue an error from inside
+	 * of C function.
+	 */
+	for (int i = 1; i <= field_count; i++) {
+		int val = mp_decode_uint(&args);
+		int needed = 2 * i;
+		if (val != needed) {
+			char res[128];
+			snprintf(res, sizeof(res), "%s %d != %d",
+				 "invalid argument", val, needed);
+			return box_error_set(__FILE__, __LINE__,
+					     ER_PROC_C, "%s", res);
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Return one element array twice.
+ */
+int
+cfunc_multireturn(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	char tuple_buf[512];
+	char *d = tuple_buf;
+	d = mp_encode_array(d, 1);
+	d = mp_encode_uint(d, 1);
+	assert(d <= tuple_buf + sizeof(tuple_buf));
+
+	box_tuple_format_t *fmt = box_tuple_format_default();
+	box_tuple_t *tuple_a = box_tuple_new(fmt, tuple_buf, d);
+	if (tuple_a == NULL)
+		return -1;
+	int rc = box_return_tuple(ctx, tuple_a);
+	if (rc == 0)
+		return box_return_tuple(ctx, tuple_a);
+	return rc;
+}
+
+/*
+ * Encode int + string pair back.
+ */
+int
+cfunc_args(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	uint32_t arg_count = mp_decode_array(&args);
+	if (arg_count != 2) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid argument count");
+	}
+
+	if (mp_typeof(*args) != MP_UINT) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "tuple field must be uint");
+	}
+	uint32_t num = mp_decode_uint(&args);
+
+	if (mp_typeof(*args) != MP_STR) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "tuple field must be string");
+	}
+	const char *str = args;
+	uint32_t len = mp_decode_strl(&str);
+
+	char tuple_buf[512];
+	char *d = tuple_buf;
+	d = mp_encode_array(d, 2);
+	d = mp_encode_uint(d, num);
+	d = mp_encode_str(d, str, len);
+	assert(d <= tuple_buf + sizeof(tuple_buf));
+
+	box_tuple_format_t *fmt = box_tuple_format_default();
+	box_tuple_t *tuple = box_tuple_new(fmt, tuple_buf, d);
+	if (tuple == NULL)
+		return -1;
+
+	return box_return_tuple(ctx, tuple);
+}
+
+/*
+ * Sum two integers.
+ */
+int
+cfunc_sum(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	uint32_t arg_count = mp_decode_array(&args);
+	if (arg_count != 2) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid argument count");
+	}
+	uint64_t a = mp_decode_uint(&args);
+	uint64_t b = mp_decode_uint(&args);
+
+	char res[16];
+	char *end = mp_encode_uint(res, a + b);
+	box_return_mp(ctx, res, end);
+	return 0;
+}
diff --git a/test/box/cfunc3.c b/test/box/cfunc3.c
new file mode 100644
index 000000000..668790fbf
--- /dev/null
+++ b/test/box/cfunc3.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <msgpuck.h>
+
+#include "module.h"
+
+/*
+ * Sum two integers.
+ */
+int
+cfunc_add(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	uint32_t arg_count = mp_decode_array(&args);
+	if (arg_count != 2) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid argument count");
+	}
+	uint64_t a = mp_decode_uint(&args);
+	uint64_t b = mp_decode_uint(&args);
+
+	char res[16];
+	char *end = mp_encode_uint(res, a + b);
+	box_return_mp(ctx, res, end);
+	return 0;
+}
diff --git a/test/box/cfunc4.c b/test/box/cfunc4.c
new file mode 100644
index 000000000..cc079b335
--- /dev/null
+++ b/test/box/cfunc4.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <msgpuck.h>
+
+#include "module.h"
+
+/*
+ * Sum two integers and add a constant,
+ * so that result will be different after
+ * the reload.
+ */
+int
+cfunc_add(box_function_ctx_t *ctx, const char *args, const char *args_end)
+{
+	const uint32_t delta = 10;
+	uint32_t arg_count = mp_decode_array(&args);
+	if (arg_count != 2) {
+		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
+				     "invalid argument count");
+	}
+	uint64_t a = mp_decode_uint(&args);
+	uint64_t b = mp_decode_uint(&args);
+
+	char res[16];
+	char *end = mp_encode_uint(res, a + b + delta);
+	box_return_mp(ctx, res, end);
+	return 0;
+}
diff --git a/test/box/cmod.result b/test/box/cmod.result
new file mode 100644
index 000000000..12a78b6b7
--- /dev/null
+++ b/test/box/cmod.result
@@ -0,0 +1,530 @@
+-- test-run result file version 2
+--
+-- gh-4642: New cmod module to be able to
+-- run C stored functions on read only nodes
+-- without requirement to register them with
+-- box.schema.func help.
+--
+build_path = os.getenv("BUILDDIR")
+ | ---
+ | ...
+package.cpath = build_path..'/test/box/?.so;'..build_path..'/test/box/?.dylib;'..package.cpath
+ | ---
+ | ...
+
+cmod = require('cmod')
+ | ---
+ | ...
+fio = require('fio')
+ | ---
+ | ...
+
+ext = (jit.os == "OSX" and "dylib" or "so")
+ | ---
+ | ...
+
+cfunc_path = fio.pathjoin(build_path, "test/box/cfunc.") .. ext
+ | ---
+ | ...
+cfunc1_path = fio.pathjoin(build_path, "test/box/cfunc1.") .. ext
+ | ---
+ | ...
+cfunc2_path = fio.pathjoin(build_path, "test/box/cfunc2.") .. ext
+ | ---
+ | ...
+cfunc3_path = fio.pathjoin(build_path, "test/box/cfunc3.") .. ext
+ | ---
+ | ...
+cfunc4_path = fio.pathjoin(build_path, "test/box/cfunc4.") .. ext
+ | ---
+ | ...
+
+_ = pcall(fio.unlink(cfunc_path))
+ | ---
+ | ...
+fio.symlink(cfunc1_path, cfunc_path)
+ | ---
+ | - true
+ | ...
+
+_, err = pcall(cmod.load, 'non-such-module')
+ | ---
+ | ...
+assert(err ~= nil)
+ | ---
+ | - true
+ | ...
+
+-- All functions are sitting in cfunc.so.
+old_module = cmod.load('cfunc')
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 1)
+ | ---
+ | - true
+ | ...
+old_module_copy = cmod.load('cfunc')
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 2)
+ | ---
+ | - true
+ | ...
+assert(old_module_copy['tt_dev.refs'] == 2)
+ | ---
+ | - true
+ | ...
+old_module_copy:unload()
+ | ---
+ | - true
+ | ...
+assert(old_module['tt_dev.refs'] == 1)
+ | ---
+ | - true
+ | ...
+old_cfunc_nop = old_module:load('cfunc_nop')
+ | ---
+ | ...
+old_cfunc_fetch_seq_evens = old_module:load('cfunc_fetch_seq_evens')
+ | ---
+ | ...
+old_cfunc_multireturn = old_module:load('cfunc_multireturn')
+ | ---
+ | ...
+old_cfunc_args = old_module:load('cfunc_args')
+ | ---
+ | ...
+old_cfunc_sum = old_module:load('cfunc_sum')
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 6)
+ | ---
+ | - true
+ | ...
+
+-- Test for error on nonexisting function.
+_, err = pcall(old_module.load, old_module, 'no-such-func')
+ | ---
+ | ...
+assert(err ~= nil)
+ | ---
+ | - true
+ | ...
+
+-- Make sure they all are callable.
+old_cfunc_nop()
+ | ---
+ | ...
+old_cfunc_fetch_seq_evens()
+ | ---
+ | ...
+old_cfunc_multireturn()
+ | ---
+ | ...
+old_cfunc_args()
+ | ---
+ | ...
+old_cfunc_sum()
+ | ---
+ | ...
+
+-- Unload the module but keep old functions alive, so
+-- they keep reference to NOP module internally
+-- and still callable.
+old_module:unload()
+ | ---
+ | - true
+ | ...
+-- Test refs via function name.
+assert(old_cfunc_nop['tt_dev.module.refs'] == 5)
+ | ---
+ | - true
+ | ...
+old_cfunc_nop()
+ | ---
+ | ...
+old_cfunc_fetch_seq_evens()
+ | ---
+ | ...
+old_cfunc_multireturn()
+ | ---
+ | ...
+old_cfunc_args()
+ | ---
+ | ...
+old_cfunc_sum()
+ | ---
+ | ...
+
+-- The module is unloaded I should not be able
+-- to load new shared library.
+old_module:load('cfunc')
+ | ---
+ | - error: Expects function = module:load('name') but not module object passed
+ | ...
+-- Neither I should be able to unload module twise.
+old_module:unload()
+ | ---
+ | - error: The module is unloaded
+ | ...
+
+-- Clean old functions.
+old_cfunc_nop:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_fetch_seq_evens:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_multireturn:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_args:unload()
+ | ---
+ | - true
+ | ...
+assert(old_cfunc_sum['tt_dev.module.refs'] == 1)
+ | ---
+ | - true
+ | ...
+old_cfunc_sum:unload()
+ | ---
+ | - true
+ | ...
+
+-- And reload old module again.
+old_module = cmod.load('cfunc')
+ | ---
+ | ...
+old_module_ptr = old_module['tt_dev.ptr']
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 1)
+ | ---
+ | - true
+ | ...
+
+-- Overwrite module with new contents.
+_ = pcall(fio.unlink(cfunc_path))
+ | ---
+ | ...
+fio.symlink(cfunc2_path, cfunc_path)
+ | ---
+ | - true
+ | ...
+
+-- Load new module, cache should be updated.
+new_module = cmod.load('cfunc')
+ | ---
+ | ...
+new_module_ptr = new_module['tt_dev.ptr']
+ | ---
+ | ...
+
+-- Old and new module keep one reference with
+-- different IDs.
+assert(old_module['tt_dev.refs'] == 1)
+ | ---
+ | - true
+ | ...
+assert(old_module['tt_dev.refs'] == new_module['tt_dev.refs'])
+ | ---
+ | - true
+ | ...
+assert(old_module_ptr ~= new_module_ptr)
+ | ---
+ | - true
+ | ...
+
+-- All functions from old module should be loadable.
+old_cfunc_nop = old_module:load('cfunc_nop')
+ | ---
+ | ...
+old_cfunc_fetch_seq_evens = old_module:load('cfunc_fetch_seq_evens')
+ | ---
+ | ...
+old_cfunc_multireturn = old_module:load('cfunc_multireturn')
+ | ---
+ | ...
+old_cfunc_args = old_module:load('cfunc_args')
+ | ---
+ | ...
+old_cfunc_sum = old_module:load('cfunc_sum')
+ | ---
+ | ...
+assert(old_cfunc_nop['tt_dev.module.ptr'] == old_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(old_cfunc_fetch_seq_evens['tt_dev.module.ptr'] == old_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(old_cfunc_multireturn['tt_dev.module.ptr'] == old_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(old_cfunc_args['tt_dev.module.ptr'] == old_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(old_cfunc_sum['tt_dev.module.ptr'] == old_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(old_module['tt_dev.refs'] == 6)
+ | ---
+ | - true
+ | ...
+
+-- Lookup for updated symbols.
+new_cfunc_nop = new_module:load('cfunc_nop')
+ | ---
+ | ...
+new_cfunc_fetch_seq_evens = new_module:load('cfunc_fetch_seq_evens')
+ | ---
+ | ...
+new_cfunc_multireturn = new_module:load('cfunc_multireturn')
+ | ---
+ | ...
+new_cfunc_args = new_module:load('cfunc_args')
+ | ---
+ | ...
+new_cfunc_sum = new_module:load('cfunc_sum')
+ | ---
+ | ...
+assert(new_cfunc_nop['tt_dev.module.ptr'] == new_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(new_cfunc_fetch_seq_evens['tt_dev.module.ptr'] == new_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(new_cfunc_multireturn['tt_dev.module.ptr'] == new_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(new_cfunc_args['tt_dev.module.ptr'] == new_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(new_cfunc_sum['tt_dev.module.ptr'] == new_module_ptr)
+ | ---
+ | - true
+ | ...
+assert(new_module['tt_dev.refs'] == 6)
+ | ---
+ | - true
+ | ...
+
+-- Call old functions.
+old_cfunc_nop()
+ | ---
+ | ...
+old_cfunc_fetch_seq_evens()
+ | ---
+ | ...
+old_cfunc_multireturn()
+ | ---
+ | ...
+old_cfunc_args()
+ | ---
+ | ...
+old_cfunc_sum()
+ | ---
+ | ...
+
+-- Call new functions.
+new_cfunc_nop()
+ | ---
+ | ...
+new_cfunc_multireturn()
+ | ---
+ | - [1]
+ | - [1]
+ | ...
+new_cfunc_fetch_seq_evens({2,4,6})
+ | ---
+ | ...
+new_cfunc_fetch_seq_evens({1,2,3})  -- error, odd numbers sequence
+ | ---
+ | - error: invalid argument 1 != 2
+ | ...
+new_cfunc_args(1, "hello")
+ | ---
+ | - [1, 'hello']
+ | ...
+new_cfunc_sum(1) -- error, one arg passed
+ | ---
+ | - error: invalid argument count
+ | ...
+new_cfunc_sum(1,2)
+ | ---
+ | - 3
+ | ...
+
+-- Cleanup old module's functions.
+old_cfunc_nop:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_fetch_seq_evens:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_multireturn:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_args:unload()
+ | ---
+ | - true
+ | ...
+old_cfunc_sum:unload()
+ | ---
+ | - true
+ | ...
+old_module:unload()
+ | ---
+ | - true
+ | ...
+
+-- Cleanup new module data.
+new_cfunc_nop:unload()
+ | ---
+ | - true
+ | ...
+new_cfunc_multireturn:unload()
+ | ---
+ | - true
+ | ...
+new_cfunc_fetch_seq_evens:unload()
+ | ---
+ | - true
+ | ...
+new_cfunc_args:unload()
+ | ---
+ | - true
+ | ...
+new_cfunc_sum:unload()
+ | ---
+ | - true
+ | ...
+new_module:unload()
+ | ---
+ | - true
+ | ...
+
+-- Cleanup the generated symlink.
+_ = pcall(fio.unlink(cfunc_path))
+ | ---
+ | ...
+
+-- Test double hashing: create function
+-- in box.schema.fun so that it should
+-- appear in cmod hash.
+fio.symlink(cfunc3_path, cfunc_path)
+ | ---
+ | - true
+ | ...
+box.schema.func.create('cfunc.cfunc_add', {language = "C"})
+ | ---
+ | ...
+box.schema.user.grant('guest', 'execute', 'function', 'cfunc.cfunc_add')
+ | ---
+ | ...
+box.func['cfunc.cfunc_add']:call({1,2})
+ | ---
+ | - 3
+ | ...
+
+old_module = cmod.load('cfunc')
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 3) -- one for cmod + 2 box instances
+ | ---
+ | - true
+ | ...
+old_func = old_module:load('cfunc_add')
+ | ---
+ | ...
+assert(old_module['tt_dev.refs'] == 4) -- plus function instance
+ | ---
+ | - true
+ | ...
+old_func(1,2)
+ | ---
+ | - 3
+ | ...
+
+-- Now update on disk and reload the module.
+_ = pcall(fio.unlink(cfunc_path))
+ | ---
+ | ...
+fio.symlink(cfunc4_path, cfunc_path)
+ | ---
+ | - true
+ | ...
+
+box.schema.func.reload("cfunc")
+ | ---
+ | ...
+box.func['cfunc.cfunc_add']:call({1,2})
+ | ---
+ | - 13
+ | ...
+
+-- The cmod instance should carry own
+-- references to the module and old
+-- function. And reloading must not
+-- affect old functions. Thus one for
+-- cmod and one for cmod function.
+assert(old_module['tt_dev.refs'] == 2)
+ | ---
+ | - true
+ | ...
+old_func(1,2)
+ | ---
+ | - 3
+ | ...
+old_func:unload()
+ | ---
+ | - true
+ | ...
+old_module:unload()
+ | ---
+ | - true
+ | ...
+
+-- Same time the reload should update
+-- low level module cache, thus two
+-- for box and box function plus one
+-- new cmod.
+new_module = cmod.load('cfunc')
+ | ---
+ | ...
+assert(new_module['tt_dev.refs'] == 3)
+ | ---
+ | - true
+ | ...
+
+-- Box function should carry own module.
+box.func['cfunc.cfunc_add']:call({1,2})
+ | ---
+ | - 13
+ | ...
+
+-- Cleanup.
+_ = pcall(fio.unlink(cfunc_path))
+ | ---
+ | ...
+new_module:unload()
+ | ---
+ | - true
+ | ...
+box.schema.func.drop('cfunc.cfunc_add')
+ | ---
+ | ...
diff --git a/test/box/cmod.test.lua b/test/box/cmod.test.lua
new file mode 100644
index 000000000..5dac237d9
--- /dev/null
+++ b/test/box/cmod.test.lua
@@ -0,0 +1,203 @@
+--
+-- gh-4642: New cmod module to be able to
+-- run C stored functions on read only nodes
+-- without requirement to register them with
+-- box.schema.func help.
+--
+build_path = os.getenv("BUILDDIR")
+package.cpath = build_path..'/test/box/?.so;'..build_path..'/test/box/?.dylib;'..package.cpath
+
+cmod = require('cmod')
+fio = require('fio')
+
+ext = (jit.os == "OSX" and "dylib" or "so")
+
+cfunc_path = fio.pathjoin(build_path, "test/box/cfunc.") .. ext
+cfunc1_path = fio.pathjoin(build_path, "test/box/cfunc1.") .. ext
+cfunc2_path = fio.pathjoin(build_path, "test/box/cfunc2.") .. ext
+cfunc3_path = fio.pathjoin(build_path, "test/box/cfunc3.") .. ext
+cfunc4_path = fio.pathjoin(build_path, "test/box/cfunc4.") .. ext
+
+_ = pcall(fio.unlink(cfunc_path))
+fio.symlink(cfunc1_path, cfunc_path)
+
+_, err = pcall(cmod.load, 'non-such-module')
+assert(err ~= nil)
+
+-- All functions are sitting in cfunc.so.
+old_module = cmod.load('cfunc')
+assert(old_module['tt_dev.refs'] == 1)
+old_module_copy = cmod.load('cfunc')
+assert(old_module['tt_dev.refs'] == 2)
+assert(old_module_copy['tt_dev.refs'] == 2)
+old_module_copy:unload()
+assert(old_module['tt_dev.refs'] == 1)
+old_cfunc_nop = old_module:load('cfunc_nop')
+old_cfunc_fetch_seq_evens = old_module:load('cfunc_fetch_seq_evens')
+old_cfunc_multireturn = old_module:load('cfunc_multireturn')
+old_cfunc_args = old_module:load('cfunc_args')
+old_cfunc_sum = old_module:load('cfunc_sum')
+assert(old_module['tt_dev.refs'] == 6)
+
+-- Test for error on nonexisting function.
+_, err = pcall(old_module.load, old_module, 'no-such-func')
+assert(err ~= nil)
+
+-- Make sure they all are callable.
+old_cfunc_nop()
+old_cfunc_fetch_seq_evens()
+old_cfunc_multireturn()
+old_cfunc_args()
+old_cfunc_sum()
+
+-- Unload the module but keep old functions alive, so
+-- they keep reference to NOP module internally
+-- and still callable.
+old_module:unload()
+-- Test refs via function name.
+assert(old_cfunc_nop['tt_dev.module.refs'] == 5)
+old_cfunc_nop()
+old_cfunc_fetch_seq_evens()
+old_cfunc_multireturn()
+old_cfunc_args()
+old_cfunc_sum()
+
+-- The module is unloaded I should not be able
+-- to load new shared library.
+old_module:load('cfunc')
+-- Neither I should be able to unload module twise.
+old_module:unload()
+
+-- Clean old functions.
+old_cfunc_nop:unload()
+old_cfunc_fetch_seq_evens:unload()
+old_cfunc_multireturn:unload()
+old_cfunc_args:unload()
+assert(old_cfunc_sum['tt_dev.module.refs'] == 1)
+old_cfunc_sum:unload()
+
+-- And reload old module again.
+old_module = cmod.load('cfunc')
+old_module_ptr = old_module['tt_dev.ptr']
+assert(old_module['tt_dev.refs'] == 1)
+
+-- Overwrite module with new contents.
+_ = pcall(fio.unlink(cfunc_path))
+fio.symlink(cfunc2_path, cfunc_path)
+
+-- Load new module, cache should be updated.
+new_module = cmod.load('cfunc')
+new_module_ptr = new_module['tt_dev.ptr']
+
+-- Old and new module keep one reference with
+-- different IDs.
+assert(old_module['tt_dev.refs'] == 1)
+assert(old_module['tt_dev.refs'] == new_module['tt_dev.refs'])
+assert(old_module_ptr ~= new_module_ptr)
+
+-- All functions from old module should be loadable.
+old_cfunc_nop = old_module:load('cfunc_nop')
+old_cfunc_fetch_seq_evens = old_module:load('cfunc_fetch_seq_evens')
+old_cfunc_multireturn = old_module:load('cfunc_multireturn')
+old_cfunc_args = old_module:load('cfunc_args')
+old_cfunc_sum = old_module:load('cfunc_sum')
+assert(old_cfunc_nop['tt_dev.module.ptr'] == old_module_ptr)
+assert(old_cfunc_fetch_seq_evens['tt_dev.module.ptr'] == old_module_ptr)
+assert(old_cfunc_multireturn['tt_dev.module.ptr'] == old_module_ptr)
+assert(old_cfunc_args['tt_dev.module.ptr'] == old_module_ptr)
+assert(old_cfunc_sum['tt_dev.module.ptr'] == old_module_ptr)
+assert(old_module['tt_dev.refs'] == 6)
+
+-- Lookup for updated symbols.
+new_cfunc_nop = new_module:load('cfunc_nop')
+new_cfunc_fetch_seq_evens = new_module:load('cfunc_fetch_seq_evens')
+new_cfunc_multireturn = new_module:load('cfunc_multireturn')
+new_cfunc_args = new_module:load('cfunc_args')
+new_cfunc_sum = new_module:load('cfunc_sum')
+assert(new_cfunc_nop['tt_dev.module.ptr'] == new_module_ptr)
+assert(new_cfunc_fetch_seq_evens['tt_dev.module.ptr'] == new_module_ptr)
+assert(new_cfunc_multireturn['tt_dev.module.ptr'] == new_module_ptr)
+assert(new_cfunc_args['tt_dev.module.ptr'] == new_module_ptr)
+assert(new_cfunc_sum['tt_dev.module.ptr'] == new_module_ptr)
+assert(new_module['tt_dev.refs'] == 6)
+
+-- Call old functions.
+old_cfunc_nop()
+old_cfunc_fetch_seq_evens()
+old_cfunc_multireturn()
+old_cfunc_args()
+old_cfunc_sum()
+
+-- Call new functions.
+new_cfunc_nop()
+new_cfunc_multireturn()
+new_cfunc_fetch_seq_evens({2,4,6})
+new_cfunc_fetch_seq_evens({1,2,3})  -- error, odd numbers sequence
+new_cfunc_args(1, "hello")
+new_cfunc_sum(1) -- error, one arg passed
+new_cfunc_sum(1,2)
+
+-- Cleanup old module's functions.
+old_cfunc_nop:unload()
+old_cfunc_fetch_seq_evens:unload()
+old_cfunc_multireturn:unload()
+old_cfunc_args:unload()
+old_cfunc_sum:unload()
+old_module:unload()
+
+-- Cleanup new module data.
+new_cfunc_nop:unload()
+new_cfunc_multireturn:unload()
+new_cfunc_fetch_seq_evens:unload()
+new_cfunc_args:unload()
+new_cfunc_sum:unload()
+new_module:unload()
+
+-- Cleanup the generated symlink.
+_ = pcall(fio.unlink(cfunc_path))
+
+-- Test double hashing: create function
+-- in box.schema.fun so that it should
+-- appear in cmod hash.
+fio.symlink(cfunc3_path, cfunc_path)
+box.schema.func.create('cfunc.cfunc_add', {language = "C"})
+box.schema.user.grant('guest', 'execute', 'function', 'cfunc.cfunc_add')
+box.func['cfunc.cfunc_add']:call({1,2})
+
+old_module = cmod.load('cfunc')
+assert(old_module['tt_dev.refs'] == 3) -- one for cmod + 2 box instances
+old_func = old_module:load('cfunc_add')
+assert(old_module['tt_dev.refs'] == 4) -- plus function instance
+old_func(1,2)
+
+-- Now update on disk and reload the module.
+_ = pcall(fio.unlink(cfunc_path))
+fio.symlink(cfunc4_path, cfunc_path)
+
+box.schema.func.reload("cfunc")
+box.func['cfunc.cfunc_add']:call({1,2})
+
+-- The cmod instance should carry own
+-- references to the module and old
+-- function. And reloading must not
+-- affect old functions. Thus one for
+-- cmod and one for cmod function.
+assert(old_module['tt_dev.refs'] == 2)
+old_func(1,2)
+old_func:unload()
+old_module:unload()
+
+-- Same time the reload should update
+-- low level module cache, thus two
+-- for box and box function plus one
+-- new cmod.
+new_module = cmod.load('cfunc')
+assert(new_module['tt_dev.refs'] == 3)
+
+-- Box function should carry own module.
+box.func['cfunc.cfunc_add']:call({1,2})
+
+-- Cleanup.
+_ = pcall(fio.unlink(cfunc_path))
+new_module:unload()
+box.schema.func.drop('cfunc.cfunc_add')
diff --git a/test/box/suite.ini b/test/box/suite.ini
index d5f72e559..9ed67178b 100644
--- a/test/box/suite.ini
+++ b/test/box/suite.ini
@@ -2,7 +2,7 @@
 core = tarantool
 description = Database tests
 script = box.lua
-disabled = rtree_errinj.test.lua tuple_bench.test.lua
+disabled = rtree_errinj.test.lua tuple_bench.test.lua cmod.test.lua
 long_run = huge_field_map_long.test.lua
 config = engine.cfg
 release_disabled = errinj.test.lua errinj_index.test.lua rtree_errinj.test.lua upsert_errinj.test.lua iproto_stress.test.lua gh-4648-func-load-unload.test.lua
-- 
2.29.2