Using asio standalone headers library

Question

This is how my CMakeLists.txt looks like

I downloaded the asio library from here. It consists of many header files that you have to include in your project. The problem is that those headers are inside directories and the #include statements just don't match the correct directory.

For example, they have a asio/async_result.hpp file. That file includes asio/detail/config.hpp. However it should be ../asio/detail/config.hpp

What am I supposed to do ? Single handily rename all those 200 header files to fit the correct directory structure ? Why are they wrong out of the box ?

Answer 1

You have to install these headers first. On most systems (aside from windows, of course), there's a typical path where such include files end up.

It's the job of your project's build system (e.g. Cmake) to find asio on your computer and configure the compiler so, that it looks in those folders, and finds the right files if you do

#include <asio/handler_type.hpp>

Do never create your project within the libary you're using (unless, of course, you want to change/extend that library). Create a project somewhere else and tell cmake to look for asio.

Also, unless your source code is part of the library itself, you should never include _detail.hpp files; these are typically not part of the API that users of a library make use of, but internal structures.

EDIT

As noted above, asio is now part of boost, so install boost including its boost::asio module correctly, instruct cmake to

 find_package(Boost COMPONENTS asio)

and use for example

 #include <boost/asio.hpp>
 #include <boost/thread/thread.hpp>

Refer to the official Boost asio Tutorial for more examples.

Answer 2

here's a simple CMake script that builds the example HTTP client, using ASIO standalone, set to generate a Visual Studio 2019 project with

cmake -H. -Bbuild -G "Visual Studio 16 2019" -A x64 

https://think-async.com/Asio/AsioStandalone.html

(no boost). Assumes source in folder asio-1.12.2

cmake_minimum_required(VERSION 3.1)
project (asio)

set(CMAKE_CXX_STANDARD 11)
add_definitions(-DASIO_STANDALONE)
add_definitions(-DASIO_HAS_STD_ADDRESSOF)
add_definitions(-DASIO_HAS_STD_ARRAY)
add_definitions(-DASIO_HAS_CSTDINT)
add_definitions(-DASIO_HAS_STD_SHARED_PTR)
add_definitions(-DASIO_HAS_STD_TYPE_TRAITS)
add_definitions(-DASIO_HAS_VARIADIC_TEMPLATES)
add_definitions(-DASIO_HAS_STD_FUNCTION)
add_definitions(-DASIO_HAS_STD_CHRONO)
add_definitions(-DBOOST_ALL_NO_LIB)
add_definitions(-D_WIN32_WINNT=0x0501)
add_definitions(-D_WINSOCK_DEPRECATED_NO_WARNINGS)

include_directories(asio-1.12.2/include)
add_executable(sync_client asio-1.12.2/src/examples/cpp11/socks4/sync_client.cpp)

Answer 3

Here is my working updated CMakeLists.txt:

cmake_minimum_required(VERSION 3.3)
project(server_client)

# take a look at the -I command
# this will incude all the header files in your project. So simple
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -I C:/Users/Shiro/Desktop/asio-1.10.6/include")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${GCC_COVERAGE_LINK_FLAGS} -static")
# Don't forget this! The libws2_re.lib library is 100% required for windows !
# I also added libwsock32.lib, not sure if thats necessary
# Those .lib files are located at C:\MinGW\lib on my machine
# That directory is located automatically, you don't have to add the full path
link_libraries(ws2_32 wsock32)


set(SOURCE_FILES chat_server.cpp)
add_executable(server_client ${SOURCE_FILES})

On my your source .cpp file you have to add

// this is required otherwise asio tries to include 
// other boost libraries which you won't have installed
// or you could add a -DASIO_STANDALONE flag right next to -std=c++11 in CMakeLists.txt
#define ASIO_STANDALONE  

#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0501 // windows stuff, not sure what this does
#endif

#include <asio.hpp> // include asio library