logsys

A C++17 high performance log messages library.

Configuration

You can use this libery in two different ways. As header-only library or as linkable library.

If you want to use the log library in a application project, you can configure the log library completely at compile time and use the header-only approach.

If you want to use the log library in another dynamic link libary, the linkable approach is the way to go. You will lose a little performance in exchange for the configurability of the log library in the main application that uses your library.

Build and install

If you want to install it for all users:

cmake /path/to/logsys
make
make install

If you want to install it without root permissions:

cmake -DCMAKE_INSTALL_PREFIX=$HOME/.local /path/to/logsys
make
make install

When you installed the library, you can use find_package(logsys) in your CMakeLists.txt. It will define ${logsys_INCLUDE_DIR} and ${logsys_LIB_DIR} which you can use in include_directories and link_directories to add the installed library to your header/lib search paths.

If you installed it with CMAKE_INSTALL_PREFIX, you have to use CMAKE_PREFIX_PATH by configuring your own project, otherwise find_package(logsys) will not find logsys.

cmake -DCMAKE_PREFIX_PATH=$HOME/.local /path/to/your/project
make

Build and run examples

Build and run by:

cmake -DLOGSYS_BUILD_EXAMPLES=ON /path/to/concurrent_queue
make
run-parts -v ./examples

Build and run unit tests

Build and run by:

cmake -DLOGSYS_BUILD_TESTS=ON /path/to/concurrent_queue
make
./test/tests

Usage

There are three functions you need to know:

• Log a message
• Log a message bound to a code block
• Log a message bound to a code block and catch any exceptions

Log a message

template < typename LogFn >
void
log(LogFn&& message_producer)
noexcept;

• throw: Never

Example 1

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    logsys::log(
        [](logsys::stdlog& log){
            log << "Hello World!";
        });
}

Output

000000 2018-11-30 11:01:15 473.307 ( no content     ) Hello World!

Example 2

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main()try{
    logsys::log(
        [throw_exception = true](logsys::stdlog& log){
            log << "Hello ";
            if(throw_exception){
                throw std::logic_error("throw in log fn!");
            }
            log << "World!";
        });
}catch(std::exception const& e){
    std::cerr << "program terminated with exception: " << e.what() << '\n';
}

Output

000000 2018-11-30 11:01:17 613.086 ( no content     ) LOG EXCEPTION CATCHED: [std::logic_error] throw in log fn!; Probably incomplete log message: 'Hello '

Log a message bound to a code block

template < typename LogFn, typename BodyFn >
std::invoke_result_t< BodyFn& >
log(LogFn&& message_producer, BodyFn&& body_fn)
noexcept(std::is_nothrow_invocable_v< BodyFn& >);

• throw: Same as body_fn()

Example 1

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    logsys::log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        []{
            std::cout << "Hello World!\n";
        });
}

Output

Hello World!
000000 2018-11-30 11:01:21 301.842 (        0.052ms ) calculate 5+5

Example 2

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    int value = logsys::log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        []{
            return 5 + 5;
        });

    std::cout << "Value: " << value << '\n';
}

Output

000000 2018-11-30 11:01:23 088.971 (        0.004ms ) calculate 5+5
Value: 10

Example 3

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main()try{
    int value = logsys::log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        [throw_exception = true]{
            if(throw_exception){
                throw std::runtime_error("something failed");
            }
            return 5 + 5;
        });

    std::cout << "Value: " << value << '\n';
}catch(std::exception const& e){
    std::cerr << "program terminated with exception: " << e.what() << '\n';
}

Output

000000 2018-11-30 11:12:02 951.863 (        0.090ms ) calculate 5+5 (BODY FAILED: [std::runtime_error] something failed)
program terminated with exception: something failed

Log a message bound to a code block and catch any exceptions

template < typename LogFn, typename BodyFn >
logsys::optional< std::invoke_result_t< BodyFn& > >
exception_catching_log(LogFn&& message_producer, BodyFn&& body_fn)
noexcept;

Example 1

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    bool success = logsys::exception_catching_log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        []{
            std::cout << "Hello World!\n";
        });

    std::cout << std::boolalpha << "success: " << success << '\n';
}

Output

Hello World!
000000 2018-11-30 11:01:28 718.579 (        0.048ms ) calculate 5+5
success: true

Example 2

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    bool success = logsys::exception_catching_log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        []{
            throw std::runtime_error("something failed");
        });

    std::cout << std::boolalpha << "success: " << success << '\n';
}

Output

000000 2018-11-30 11:12:25 372.583 (        0.089ms ) calculate 5+5 (BODY EXCEPTION CATCHED: [std::runtime_error] something failed)
success: false

Example 3

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    std::optional< int > value = logsys::exception_catching_log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        []{
            return 5 + 5;
        });

    auto success = static_cast< bool >(value);
    std::cout << std::boolalpha << "success: " << success << '\n';

    if(success){
        std::cout << "Value: " << *value << '\n';
    }
}

Output

000000 2018-11-30 11:01:30 811.171 (        0.005ms ) calculate 5+5
success: true
Value: 10

Example 4

#include <logsys/log.hpp>
#include <logsys/stdlog.hpp>

int main(){
    std::optional< int > value = logsys::exception_catching_log(
        [](logsys::stdlog& log){
            log << "calculate 5+5";
        },
        [throw_exception = true]{
            if(throw_exception){
                throw std::runtime_error("something failed");
            }
            return 5 + 5;
        });

    auto success = static_cast< bool >(value);
    std::cout << std::boolalpha << "success: " << success << '\n';

    if(success){
        std::cout << "Value: " << *value << '\n';
    }
}

Output

000000 2018-11-30 11:12:27 174.654 (        0.096ms ) calculate 5+5 (BODY EXCEPTION CATCHED: [std::runtime_error] something failed)
success: false

• throw: Never

Optional type: logsys::optional< BodyRT >

The BodyRT is the return type of your body function.

• logsys::optional< void > is bool
• logsys::optional< T > is std::optional< T >
• logsys::optional< T& > is logsys::optional_lvalue_reference< T >
• logsys::optional< T&& > is logsys::optional_rvalue_reference< T >

The last two definitions are uncommon. If you really return a reference from your body function, checkout the definitions of logsys::optional_lvalue_reference< T > and logsys::optional_rvalue_reference< T > in optional.hpp. They have a similar interface to std::optional.

License notice

This software was originally developed privately by Benjamin Buch. All changes are released under the Boost Software License - Version 1.0 and published on GitHub.

https://github.com/bebuch/logsys