Getting Started — conan 1.64.1 documentation (2024)

An MD5 hash calculator using the Poco Libraries

$ git clone https://github.com/conan-io/examples.git && cd examples/libraries/poco/md5

1. Create the following source file inside a folder. This will be the source file of our application:

   md5.cpp

    #include "Poco/MD5Engine.h" #include "Poco/DigestStream.h" #include <iostream> int main(int argc, char** argv){ Poco::MD5Engine md5; Poco::DigestOutputStream ds(md5); ds << "abcdefghijklmnopqrstuvwxyz"; ds.close(); std::cout << Poco::DigestEngine::digestToHex(md5.digest()) << std::endl; return 0; }

2. We know that our application relies on the Poco libraries. Let’s look for it in the ConanCenter remote,going to https://conan.io/center, and typing “poco” in the search box. We will see that there aresome different versions available:

   poco/1.8.1poco/1.9.3poco/1.9.4...

   Note

   The Conan client contains a command to search in remote repositories, and we couldtry $ conan search poco --remote=conancenter. You can perfectly use this command to search in yourown repositories, but note that at the moment this might timeout in ConanCenter. The infrastructure is beingimproved to support this command too, but meanwhile using the ConanCenter UIis recommended.

3. We got some interesting references for Poco. Let’s inspect the metadata of the 1.9.4 version:

   $ conan inspect poco/1.9.4name: pocoversion: 1.9.4url: https://github.com/conan-io/conan-center-indexhomepage: https://pocoproject.orglicense: BSL-1.0author: Nonedescription: Modern, powerful open source C++ class libraries for building network- and internet-based applications that run on desktop, server, mobile and embedded systems.topics: ('conan', 'poco', 'building', 'networking', 'server', 'mobile', 'embedded')generators: cmakeexports: Noneexports_sources: CMakeLists.txtshort_paths: Falseapply_env: Truebuild_policy: Nonerevision_mode: hashsettings: ('os', 'arch', 'compiler', 'build_type')options: cxx_14: [True, False] enable_apacheconnector: [True, False] enable_cppparser: [True, False] enable_crypto: [True, False] [...]default_options: cxx_14: False enable_apacheconnector: False enable_cppparser: False enable_crypto: True [...]

   See Also

   Install — conan 1.64.1 documentationconan install — conan 2.6.0 documentation

4. Let’s use this poco/1.9.4 version for our MD5 calculator app, creating a conanfile.txt inside ourproject’s folder with the following content:

   conanfile.txt

    [requires] poco/1.9.4 [generators] cmake

   In this example we are using CMake to build the project, which is why the cmake generator isspecified. This generator creates a conanbuildinfo.cmake file that defines CMake variablesincluding paths and library names that can be used in our build. Read more aboutGenerators.

5. Next step: We are going to install the required dependencies and generate the information for the build system:

   Important

   If you are using GCC compiler >= 5.1, Conan will set the compiler.libcxx to the oldABI for backwards compatibility. In the context of this getting started example, this is a bad choice though:Recent gcc versions will compile the example by default with the new ABI and linking will fail without furthercustomization of your cmake configuration. You can avoid this with the following commands:

   $ conan profile new default --detect # Generates default profile detecting GCC and sets old ABI$ conan profile update settings.compiler.libcxx=libstdc++11 default # Sets libcxx to C++11 ABI

   You will find more information in How to manage the GCC >= 5 ABI.

   $ mkdir build && cd build$ conan install .....Requirements bzip2/1.0.8 from 'conancenter' - Downloaded expat/2.2.9 from 'conancenter' - Downloaded openssl/1.1.1g from 'conancenter' - Downloaded pcre/8.41 from 'conancenter' - Downloaded poco/1.9.4 from 'conancenter' - Cache sqlite3/3.31.1 from 'conancenter' - Downloaded zlib/1.2.11 from 'conancenter' - DownloadedPackages bzip2/1.0.8:5be2b7a2110ec8acdbf9a1cea9de5d60747edb34 - Download expat/2.2.9:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Download openssl/1.1.1g:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Download pcre/8.41:20fc3dfce989c458ac2372442673140ea8028c06 - Download poco/1.9.4:73e83a21ea6817fa9ef0f7d1a86ea923190b0205 - Download sqlite3/3.31.1:4559c5d4f09161e1edf374b033b1d6464826db16 - Download zlib/1.2.11:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 - Downloadzlib/1.2.11: Retrieving package f74366f76f700cc6e991285892ad7a23c30e6d47 from remote 'conancenter'Downloading conanmanifest.txt completed [0.25k]Downloading conaninfo.txt completed [0.44k]Downloading conan_package.tgz completed [83.15k]Decompressing conan_package.tgz completed [0.00k]zlib/1.2.11: Package installed f74366f76f700cc6e991285892ad7a23c30e6d47zlib/1.2.11: Downloaded package revision 0...poco/1.9.4: Retrieving package 645aaff0a79e6036c77803601e44677556109dd9 from remote 'conancenter'Downloading conanmanifest.txt completed [48.75k]Downloading conaninfo.txt completed [2.44k]Downloading conan_package.tgz completed [5128.39k]Decompressing conan_package.tgz completed [0.00k]poco/1.9.4: Package installed 645aaff0a79e6036c77803601e44677556109dd9poco/1.9.4: Downloaded package revision 0conanfile.txt: Generator cmake created conanbuildinfo.cmakeconanfile.txt: Generator txt created conanbuildinfo.txtconanfile.txt: Generated conaninfo.txtconanfile.txt: Generated graphinfo

   Conan installed our Poco dependency but also the transitive dependencies for it: OpenSSL, zlib, sqlite and others.It has also generated a conanbuildinfo.cmake file for our build system.

   Warning

   There are prebuilt binaries for several mainstream compilers and versions available in ConanCenter repository,a list is keep in the repository’s documentationIf your current configuration is not pre-built in ConanCenter, Conan will raise a “Binary Missing” error. Pleaseread carefully the error messages. You can build the binary package from sources using conan install .. --build=missing,it will succeed if your configuration is supported by the recipe (it is possible that some ConanCenter recipes fail tobuild for some platforms). You will find more info in the Building with other configurations section.

6. Now let’s create our build file. To inject the Conan information, include the generated conanbuildinfo.cmake file like this:

   Caution

   The Creating Packages’s Getting Started is a more up-to-date version of this section.

   CMakeLists.txt

    cmake_minimum_required(VERSION 2.8.12) project(MD5Encrypter) add_definitions("-std=c++11") include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake) conan_basic_setup() add_executable(md5 md5.cpp) target_link_libraries(md5 ${CONAN_LIBS})

   Note

   There are other integrations with CMake, like the cmake_find_package generators, that willuse the find_package() CMake syntax (see CMake section).

7. Now we are ready to build and run our MD5 app:

   (win)$ cmake .. -G "Visual Studio 16"$ cmake --build . --config Release(linux, mac)$ cmake .. -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release$ cmake --build ....[100%] Built target md5$ ./bin/md5c3fcd3d76192e4007dfb496cca67e13b

Installing Dependencies

The conan install command downloads the binary package required for your configuration (detected the first time you ran thecommand), together with other (transitively required by Poco) libraries, like OpenSSL and Zlib. It will also create theconanbuildinfo.cmake file in the current directory, in which you can see the CMake variables, and a conaninfo.txt in which the settings,requirements and optional information is saved.

It is very important to understand the installation process. When the conan install command runs, settings specified on thecommand line or taken from the defaults in <userhome>/.conan/profiles/default file are applied.

For example, the command conan install .. --settings os="Linux" --settings compiler="gcc", performs these steps:

• Checks if the package recipe (for poco/1.9.4 package) exists in the local cache. If we are just starting, thecache is empty.

• Looks for the package recipe in the defined remotes. Conan comes with conancenter remote as the default, but can be changed.

• If the recipe exists, the Conan client fetches and stores it in your local Conan cache.

• With the package recipe and the input settings (Linux, GCC), Conan looks for the corresponding binary in the local cache.

• As the binary is not found in the cache, Conan looks for it in the remote and fetches it.

• Finally, it generates an appropriate file for the build system specified in the [generators] section.

Inspecting Dependencies

The retrieved packages are installed to your local user cache (typically .conan/data), and can be reused from this location for otherprojects. This allows to clean your current project and continue working even without network connection. To search for packages in thelocal cache run:

$ conan search "*"Existing package recipes:openssl/1.0.2tpoco/1.9.4zlib/1.2.11...

To inspect the different binary packages of a reference run:

$ conan search poco/1.9.4@Existing packages for recipe poco/1.9.4:Package_ID: 645aaff0a79e6036c77803601e44677556109dd9 [options] cxx_14: False enable_apacheconnector: False enable_cppparser: False enable_crypto: True enable_data: True...

The @ symbol at the end of the package name is important to search for a specific package. If youdon’t add the @, Conan will interpret the argument as a pattern search and return all thepackages that match the poco/1.9.4 pattern and may have different user and channel.

To inspect all your current project’s dependencies use the conan info command by pointing it to the location of theconanfile.txt folder:

$ conan info ..conanfile.txt ID: db91af4811b080e02ebe5a626f1d256bb90d5223 BuildID: None Requires: poco/1.9.4openssl/1.0.2t ID: eb50d18a5a5d59bd0c332464a4c348ab65e353bf BuildID: None Context: host Remote: conancenter=https://center.conan.io URL: https://github.com/conan-io/conan-center-index Homepage: https://github.com/openssl/openssl License: OpenSSL Description: A toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols Topics: conan, openssl, ssl, tls, encryption, security Recipe: Cache Binary: Cache Binary remote: conancenter Creation date: 2019-11-13 23:14:37 Required by: poco/1.9.4 Requires: zlib/1.2.11poco/1.9.4 ID: 645aaff0a79e6036c77803601e44677556109dd9 BuildID: None Context: host Remote: conancenter=https://center.conan.io URL: https://github.com/conan-io/conan-center-index Homepage: https://pocoproject.org License: BSL-1.0 Description: Modern, powerful open source C++ class libraries for building network- and internet-based applications that run on desktop, server, mobile and embedded systems. Topics: conan, poco, building, networking, server, mobile, embedded Recipe: Cache Binary: Cache Binary remote: conancenter Creation date: 2020-01-07 17:29:24 Required by: conanfile.txt Requires: openssl/1.0.2tzlib/1.2.11 ID: f74366f76f700cc6e991285892ad7a23c30e6d47 BuildID: None Context: host Remote: conancenter=https://center.conan.io URL: https://github.com/conan-io/conan-center-index Homepage: https://zlib.net License: Zlib Description: A Massively Spiffy Yet Delicately Unobtrusive Compression Library (Also Free, Not to Mention Unencumbered by Patents) Recipe: Cache Binary: Cache Binary remote: conancenter Creation date: 2020-01-07 17:01:29 Required by: openssl/1.0.2t

Or generate a graph of your dependencies using Dot or HTML formats:

$ conan info .. --graph=file.html$ file.html # or open the file, double-click

Searching Packages

The remote repository where packages are installed from is configured by default in Conan. It is called Conan Center(configured as conancenter remote).

If we search for something like open in ConanCenter we could find different packages like:

openal/1.18.2@bincrafters/stableopenal/1.19.1opencv/2.4.13.5@conan/stableopencv/3.4.3@conan/stableopencv/4.1.1@conan/stableopenexr/2.3.0openexr/2.3.0@conan/stableopenexr/2.4.0openjpeg/2.3.0@bincrafters/stableopenjpeg/2.3.1openjpeg/2.3.1@bincrafters/stableopenssl/1.0.2s...

As you can see, some of the libraries end with a @ symbol followed by two strings separated by aslash. These fields are the user and channel for the Conan package, and they areuseful if you want to make specific changes and disambiguate your modified recipe from the one in theConan Center or any other remote. These are legacy packages, and the ones without userand channel are the ones strongly recommended to use from ConanCenter.

ConanCenter is the central public repository for Conan packages. You can contribute packages to it inthe conan-center-index Github repository.If you want to store your own private packages, you can download the free Artifactory Community Edition (CE)directly from the Conan downloads page.

Building with other configurations

In this example, we have built our project using the default configuration detected by Conan. This configuration is known as thedefault profile.

A profile needs to be available prior to running commands such as conan install. When running the command, your settings areautomatically detected (compiler, architecture…) and stored as the default profile. You can edit these settings~/.conan/profiles/default or create new profiles with your desired configuration.

For example, if we have a profile with a 32-bit GCC configuration in a file called gcc_x86, we can run the following:

$ conan install .. --profile=gcc_x86

However, the user can always override the profile settings in the conan install command using the --settingsparameter. As an exercise, try building the 32-bit version of the hash calculator project like this:

$ conan install .. --settings arch=x86

The above command installs a different package, using the --settings arch=x86 instead of the one of the default profile usedpreviously. Note you might need to install extra compilers or toolchains in some platforms, as for example, Linux distributionsno longer install 32bits toolchains by default.

To use the 32-bit binaries, you will also have to change your project build:

• In Windows, change the CMake invocation to Visual Studio 14.

• In Linux, you have to add the -m32 flag to your CMakeLists.txt by running SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32"), andthe same applies to CMAKE_C_FLAGS, CMAKE_SHARED_LINK_FLAGS and CMAKE_EXE_LINKER_FLAGS. This can also be done more easily, byautomatically using Conan, as we’ll show later.

• In macOS, you need to add the definition -DCMAKE_OSX_ARCHITECTURES=i386.

Got any doubts? Check our FAQ, write us or join the community in Cpplang Slack #conan channel!