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();
 }