Linked lists are part of the most basic data structures in Computer Science. They have several advantages over arrays (Skiena, 2020):

• Overflow never occurs, unless the memory is actually full
• Insertion and deletion are simpler
• With large records, moving pointers is easier and faster

These structures use pointers to connect all the pieces in the list by giving a memory address to each item.

As a beginner in Rust, implementing a singly linked list is an opportunity to learn about dynamic memory and ownership. A crucial concept in dynamic memory is the heap: we don’t know the amount of items in the list, so this structure cannot exist in the stack memory. As each item has at most one pointer referring to it, we have unique ownership.

The source code can be found here

As discussed in Part 1, BOOST_LOG_TRIVIAL is a quick way to have a logger in a console with a predetermined formatting. Our goal is to customize the message structure and colors.

Create a console sink

The first step is to use a new macro called BOOST_LOG_SEV that receives a custom logger lg and the severity.

namespace src = boost::log::sources;

...

int main() {
  init();

  src::severity_logger<trivial::severity_level> lg;

  BOOST_LOG_SEV(lg, trivial::trace) << "A trace severity message";
  BOOST_LOG_SEV(lg, trivial::debug) << "A debug severity message";
  BOOST_LOG_SEV(lg, trivial::info) << "An informational severity message";
  BOOST_LOG_SEV(lg, trivial::warning) << "A warning severity message";
  BOOST_LOG_SEV(lg, trivial::error) << "An error severity message";
  BOOST_LOG_SEV(lg, trivial::fatal) << "A fatal severity message";

  return 0;
}

[2024-12-14 00:12:15.390463] [0x00007e195fcdf740] [debug]   A debug severity message
[2024-12-14 00:12:15.390476] [0x00007e195fcdf740] [info]    An informational severity message
[2024-12-14 00:12:15.390479] [0x00007e195fcdf740] [warning] A warning severity message
[2024-12-14 00:12:15.390481] [0x00007e195fcdf740] [error]   An error severity message
[2024-12-14 00:12:15.390482] [0x00007e195fcdf740] [fatal]   A fatal severity message

Formatting

As you can appreciate, the formatting with BOOST_LOG_SEV is the same as BOOST_LOG_TRIVIAL because Boost uses the same default sink. How do we modify the default message structure? Let’s create a custom sink that outputs to console, replacing the init method:

The source code can be found here

Basic logging

The first thing we need is to setup our project. I will use CMake as the build system.

To add Boost.Log library, is necessary to use the FindBoost module. Since version 3.30, it’s recommended to use the configuration file provided by Boost, avoiding a warning due to the policy CMP0167, therefore the usage of CONFIG in find_package.

cmake_minimum_required(VERSION 3.28)
project(MyLogger)

set(CMAKE_CXX_STANDARD 20)

find_package(Boost 1.83.0 REQUIRED COMPONENTS log log_setup CONFIG)

add_executable(custom_logger)
target_sources(custom_logger PRIVATE main.cpp)
target_link_libraries(custom_logger PRIVATE ${Boost_LIBRARIES})

custom_logger is the target (binary/executable).