Add dummy shared lib to test mef::ExternLibrary

Basic smoke tests are provided to check
if the dynamic library loading works on the given platform.

Issue #74

src/expression/extern.cc

@@ -58,7 +58,7 @@ class ExternLibrary::Pimpl {
         bool decorate) : lib_handle_(nullptr) {
     if (decorate) {
       lib_path += ".so";
-      auto pos = lib_path.find('/');
+      auto pos = lib_path.rfind('/');
       lib_path.insert(pos == std::string::npos ? 0 : (pos + 1), "lib");
     }
     if (!system || lib_path.find('/') != std::string::npos) {

src/expression/extern.h

@@ -61,12 +61,16 @@ class ExternLibrary : public Element, private boost::noncopyable {
   /// @returns The function pointer resolved from the symbol.
   ///
   /// @throws UndefinedElement  The symbol is not in the library.
+  ///
+  /// @note The functionality should fail at compile time (UB in C)
+  ///       if the platform doesn't support
+  ///       object pointer to function pointer casts.
   template <typename F>
   std::enable_if_t<std::is_pointer<F>::value &&
                        std::is_function<std::remove_pointer_t<F>>::value,
                    F>
   get(const std::string& symbol) const {
-    return static_cast<F>(get(symbol.c_str()));
+    return reinterpret_cast<F>(get(symbol.c_str()));
   }
 
  private:

tests/CMakeLists.txt

@@ -23,6 +23,7 @@ set(SCRAM_CORE_TEST_SOURCE
   "${CMAKE_CURRENT_SOURCE_DIR}/element_tests.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/event_tests.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/expression_tests.cc"
+  "${CMAKE_CURRENT_SOURCE_DIR}/extern_function_tests.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/ccf_group_tests.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/fault_tree_tests.cc"
   "${CMAKE_CURRENT_SOURCE_DIR}/alignment_tests.cc"
@@ -78,3 +79,14 @@ install(DIRECTORY
   DESTINATION share/scram
   COMPONENT testing
   )
+
+# Create dummy library to test dynamic loading and extern function.
+add_library(scram_dummy_extern SHARED "${CMAKE_CURRENT_SOURCE_DIR}/scram_dummy_extern.cc")
+if(WIN32)
+  set(CMAKE_SHARED_LIBRARY_PREFIX "")
+endif()
+install(
+  TARGETS scram_dummy_extern
+  DESTINATION lib/scram/test
+  COMPONENT testing
+  )

tests/extern_function_tests.cc

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2017 Olzhas Rakhimov
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "expression/extern.h"
+
+#include <memory>
+
+#include <gtest/gtest.h>
+
+#include <boost/predef.h>
+
+#if BOOST_OS_LINUX
+#include <stdlib.h>
+#endif
+
+#include "env.h"
+
+namespace scram {
+namespace mef {
+namespace test {
+
+const char kLibName[] = "scram_dummy_extern";
+const char kLibRelPath[] = "../lib/scram/test/scram_dummy_extern";
+
+#if BOOST_OS_LINUX
+const char kLibRelPathLinux[] = "../lib/scram/test/libscram_dummy_extern.so";
+#endif
+
+TEST(ExternTest, ExternLibraryLoad) {
+  const std::string bin_dir = Env::install_dir() + "/bin";
+  EXPECT_THROW(ExternLibrary("dummy", kLibName, "", false, false), IOError);
+  EXPECT_THROW(ExternLibrary("dummy", kLibName, "", false, true), IOError);
+  EXPECT_THROW(ExternLibrary("dummy", kLibName, "", true, true), IOError);
+  EXPECT_THROW(ExternLibrary("dummy", kLibRelPath, bin_dir, false, false),
+               IOError);
+  EXPECT_NO_THROW(ExternLibrary("dummy", kLibRelPath, bin_dir, false, true));
+  EXPECT_NO_THROW(ExternLibrary("dummy", kLibRelPath, bin_dir, true, true));
+
+#if BOOST_OS_LINUX
+  EXPECT_NO_THROW(
+      ExternLibrary("dummy", kLibRelPathLinux, bin_dir, false, false));
+  // The system search with LD_LIBRARY_PATH must be tested outside.
+#endif
+}
+
+TEST(ExternTest, ExternLibraryGet) {
+  const std::string bin_dir = Env::install_dir() + "/bin";
+
+  std::unique_ptr<ExternLibrary> library;
+  ASSERT_NO_THROW(library = std::make_unique<ExternLibrary>(
+                      "dummy", kLibRelPath, bin_dir, false, true));
+
+  EXPECT_NO_THROW(library->get<int(*)()>("foo"));
+  EXPECT_NO_THROW(library->get<double(*)()>("bar"));
+  EXPECT_NO_THROW(library->get<float(*)()>("baz"));
+  EXPECT_THROW(library->get<int(*)()>("foobar"), UndefinedElement);
+
+  EXPECT_EQ(42, library->get<int(*)()>("foo")());
+  EXPECT_EQ(42, library->get<double(*)()>("bar")());
+  EXPECT_EQ(42, library->get<float(*)()>("baz")());
+}
+
+}  // namespace test
+}  // namespace mef
+}  // namespace scram

tests/scram_dummy_extern.cc

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2017 Olzhas Rakhimov
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/// @file scram_dummy_extern.cc
+/// Dummy library with extern functions to test dynamic loading in MEF extern.
+
+extern "C" {
+  int foo() { return 42; }
+  double bar() { return 42; }
+  float baz() { return 42; }
+}