Fixed coverity in acl_hal_mmd.cpp: Resource leak (RESOURCE_LEAK)

mmd_libraries were not closed after execution, which causes memory leaks. But mmd_libraries cannot be closed trivially since closing the library invalidates the symbol return by dlsym(), which means calling the function further down is undefined behaviour.
To solve this issues, I added a `dl_wrapper_t` vector as a global initialized vector that would be deallocated when closing the runtime library. This vector would contain all the opened libraries that would be closed by the destructor of `dl_wrapper_t` once the vector deallocates.

Author: haoxian2

src/acl_hal_mmd.cpp

@@ -188,7 +188,41 @@ unsigned acl_convert_mmd_capabilities(unsigned mmd_capabilities);
 const static size_t MIN_SOF_SIZE = 1;
 const static size_t MIN_PLL_CONFIG_SIZE = 1;
 
+// Wrapper for dl libraries
+struct dl_wrapper_t {
+  std::vector<void *> mmd_libs;
+  dl_wrapper_t() { ; }
+  ~dl_wrapper_t() {
+    for (void *mmd_lib : this->mmd_libs) {
+      if (mmd_lib) {
+#ifdef _WIN32
+        FreeLibrary((HMODULE)mmd_lib);
+#else
+        dlclose(mmd_lib);
+#endif
+      }
+    }
+  }
+
+  // destroy last element of mmd_libs
+  void pop_back() {
+    if (this->mmd_libs.back()) {
+#ifdef _WIN32
+      FreeLibrary((HMODULE)this->mmd_libs.back());
+#else
+      dlclose(this->mmd_libs.back());
+#endif
+    }
+    this->mmd_libs.pop_back();
+  }
+
+  // prohibit copying to avoid double-close of handle
+  dl_wrapper_t(const dl_wrapper_t &) = delete;
+  dl_wrapper_t &operator=(const dl_wrapper_t &) = delete;
+};
+
 std::vector<acl_mmd_dispatch_t> internal_mmd_dispatch;
+static dl_wrapper_t dl_wrapper;
 
 // Dynamically load board mmd & symbols
 static size_t num_board_pkgs;
@@ -568,8 +602,9 @@ cl_bool l_load_single_board_library(const char *library_name,
       return CL_FALSE;
   }
 #endif
-  auto *mmd_library = my_dlopen(library_name, &error_msg);
-  if (!mmd_library) {
+  dl_wrapper.mmd_libs.push_back(my_dlopen(library_name, &error_msg));
+  if (!dl_wrapper.mmd_libs.back()) {
+    dl_wrapper.pop_back();
     std::cout << "Error: Could not load board library " << library_name;
     if (error_msg && error_msg[0] != '\0') {
       std::cout << " (error_msg: " << error_msg << ")";
@@ -578,18 +613,19 @@ cl_bool l_load_single_board_library(const char *library_name,
     return CL_FALSE;
   }
 
-  auto *test_symbol =
-      my_dlsym(mmd_library, "aocl_mmd_get_offline_info", &error_msg);
+  auto *test_symbol = my_dlsym(dl_wrapper.mmd_libs.back(),
+                               "aocl_mmd_get_offline_info", &error_msg);
   if (!test_symbol) {
     // On Linux, for custom libraries close the library (which was opened
     // locally) and then reopen globally. For Windows, there is no option (i.e.
     // it is always global)
 #ifdef __linux__
-    my_dlclose(mmd_library);
+    my_dlclose(dl_wrapper.mmd_libs.back());
     ACL_HAL_DEBUG_MSG_VERBOSE(
         1, "This library is a custom library. Opening globally.\n");
-    mmd_library = my_dlopen_global(library_name, &error_msg);
-    if (!mmd_library) {
+    dl_wrapper.mmd_libs.back() = my_dlopen_global(library_name, &error_msg);
+    if (!dl_wrapper.mmd_libs.back()) {
+      dl_wrapper.pop_back();
       std::cout << "Error: Could not load custom library " << library_name;
       if (error_msg && error_msg[0] != '\0') {
         std::cout << " (error_msg: " << error_msg << ")";
@@ -600,9 +636,9 @@ cl_bool l_load_single_board_library(const char *library_name,
 #endif
   } else {
     if (load_libraries) {
-      auto result =
-          l_load_board_functions(&(internal_mmd_dispatch[num_boards_found]),
-                                 library_name, mmd_library, error_msg);
+      auto result = l_load_board_functions(
+          &(internal_mmd_dispatch[num_boards_found]), library_name,
+          dl_wrapper.mmd_libs.back(), error_msg);
       if (result == CL_FALSE) {
         std::cout << "Error: Could not load board library " << library_name
                   << " due to failure to load symbols\n";
@@ -1155,9 +1191,10 @@ static acl_mmd_dispatch_t *get_msim_mmd_layer() {
       ipa_simulator ? mmd_lib_name_ipa : mmd_lib_name_aoc;
 
   char *error_msg = nullptr;
-  auto *mmd_lib = my_dlopen(mmd_lib_name, &error_msg);
+  dl_wrapper.mmd_libs.push_back(my_dlopen(mmd_lib_name, &error_msg));
   typedef acl_mmd_dispatch_t *(*fcn_type)();
-  if (!mmd_lib) {
+  if (!dl_wrapper.mmd_libs.back()) {
+    dl_wrapper.pop_back();
     std::cout << "Error: Could not load simulation MMD library "
               << mmd_lib_name;
     if (error_msg && error_msg[0] != '\0') {
@@ -1166,8 +1203,9 @@ static acl_mmd_dispatch_t *get_msim_mmd_layer() {
     std::cout << "\n";
     return nullptr;
   }
-  auto *sym = my_dlsym(mmd_lib, sym_name, &error_msg);
+  auto *sym = my_dlsym(dl_wrapper.mmd_libs.back(), sym_name, &error_msg);
   if (!sym) {
+    dl_wrapper.pop_back();
     std::cout << "Error: Symbol " << sym_name
               << " not found in simulation MMD library ";
     if (error_msg && error_msg[0] != '\0') {