Check allocator validity in some rcl_logging functions (#116)

If the allocator is zero-initialized, it may cause a segfault when it is
used later in the functions.

Signed-off-by: Scott K Logan <logans@cottsay.net>

rcl_logging_interface/src/logging_dir.c

@@ -28,6 +28,7 @@ rcl_logging_get_logging_directory(rcutils_allocator_t allocator, char ** directo
     RCUTILS_SET_ERROR_MSG("directory argument must not be null");
     return RCL_LOGGING_RET_INVALID_ARGUMENT;
   }
+  RCUTILS_CHECK_ALLOCATOR(&allocator, return RCL_LOGGING_RET_INVALID_ARGUMENT);
   if (NULL != *directory) {
     RCUTILS_SET_ERROR_MSG("directory argument must point to null");
     return RCL_LOGGING_RET_INVALID_ARGUMENT;

rcl_logging_spdlog/src/rcl_logging_spdlog.cpp

@@ -100,6 +100,8 @@ rcl_logging_ret_t rcl_logging_external_initialize(
   const char * config_file,
   rcutils_allocator_t allocator)
 {
+  RCUTILS_CHECK_ALLOCATOR(&allocator, return RCL_LOGGING_RET_INVALID_ARGUMENT);
+
   std::lock_guard<std::mutex> lk(g_logger_mutex);
   // It is possible for this to get called more than once in a process (some of
   // the tests do this implicitly by calling rclcpp::init more than once).

rcl_logging_spdlog/test/test_logging_interface.cpp

@@ -192,7 +192,7 @@ TEST_F(AllocatorTest, init_invalid)
     rcl_logging_external_initialize("anything", nullptr, bad_allocator));
   rcutils_reset_error();
   EXPECT_EQ(
-    RCL_LOGGING_RET_ERROR,
+    RCL_LOGGING_RET_INVALID_ARGUMENT,
     rcl_logging_external_initialize(nullptr, nullptr, invalid_allocator));
   rcutils_reset_error();
 }