Building Exiv2 dependencies with conan

Conan is a portable package manager for C/C++ libraries. It can be used to create all dependencies needed to build Exiv2, without needing to install system packages.

This document provides a step-by-step guide to show you the basic usage of conan. For more details about the tool, please visit the Conan documentation website.

Although we provide step-by-step instructions to enable you to build Exiv2 with conan, we recommend that you read conan's documentation to understand the main concepts: Getting started with Conan

To build Exiv2 with conan, you will also need to install CMake. https://cmake.org/download/

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T A B L E _ OF _ C O N T E N T S

1. Step by Step Guide
   1. Install conan
   2. Test conan installation
   3. Create a build directory
   4. Build dependencies and install conan artefacts in your build directory
   5. Execute cmake to generate build files for your environment:
2. Platform Notes
   1. Linux Notes
   2. Visual Studio Notes
   3. Cygwin Notes
   4. MinGW Notes
3. Conan Architecture
   1. conanfile.py
   2. Conan Recipes
   3. Conan server search path
   4. Configuring conan on your machine
4. Building Exiv2 with Adobe XMPsdk 2016
   1. Add a remote directory to conan's recipe search path
   2. Build dependencies and install conan artefacts in your build directory
   3. Execute cmake to generate build files for your environment
   4. Build Exiv2 and link Adobe XMPsdk library
5. Webready Support

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1 Step by Step Guide

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1.1) Install conan:

$ pip install conan

For other installation methods (brew, installers, from sources), visit this link.

To upgrade the version of conan:

$ pip install conan --upgrade

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1.2) Test conan installation

$ conan --version
Conan version 1.4.1

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1.3) Create a build directory<name id="1-3">

Create a build directory and will run the conan commands:

$ mkdir build
$ cd build
$ conan profile list

IMPORTANT Visual Studio Users require the profile msvc2017Release64 in %HOMEPATH%.conan\profiles\msvc2017Release64

[build_requires]
[settings]
arch=x86_64
build_type=Release
compiler=Visual Studio
compiler.runtime=MD
compiler.version=15
os=Windows
arch_build=x86_64
os_build=Windows
[options]
[env]

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1.4) Build dependencies and install conan artefacts in your build directory

Execute $ conan install pointing to the directory containing conanfile.py.

$ conan install .. --build missing  # --profile msvc2017Release64

Visual Studio Users should use --profile msvc2017Release64

The output from this command is quite long as conan downloads or builds zlib, expat, curl and other dependencies.

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1.5) Execute cmake to generate build files for your environment.

$ cmake ..  # -G "Visual Studio 15 2017 Win64"

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1.6) Build Exiv2:

$ cmake --build . --config Release

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2) Platform Notes

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2.1) Linux Notes

Default Profile

When you run conan install for the first time, it will detect and write the default profile ~/.conan/profile/default. On my Ubuntu system with GCC 4.9, this is:

[settings]
os=Linux
os_build=Linux
arch=x86_64
arch_build=x86_64
compiler=gcc
compiler.version=4.9
compiler.libcxx=libstdc++
build_type=Release
[options]
[build_requires]
[env]

Changing profile settings

One of the most important profile settings to be adjusted in your conan profile when working on Linux is the field

compiler.libcxx=libstdc++11  # Possible values: libstdc++, libstdc++11, libc++

With the arrival of the c++11 standard, and the growing popularity of the clang compiler, it is increasingly important which version of the standard library to use (corresponds to the -stdlib compiler flag).

Recommended libcxx settings works with conan and different compilers:

compiler.libcxx=libstdc++11  # will use -stdlib=libstdc++ and define _GLIBCXX_USE_CXX11_ABI=1
compiler.libcxx=libstdc++    # will use -stdlib=libstdc++ and define _GLIBCXX_USE_CXX11_ABI=0
compiler.libcxx=libc++       # will use -stdlib=libc++

As a rule of thumb, set compiler.libcxx=libstdc++11 when using a version of gcc >= 5.1.

More information about the standard library and GCC dual ABI in gcc with GCC works.

Please, be aware that normally when using gcc >= 5.1, _GLIBCXX_USE_CXX11_ABI is set to 1 by default. However some linux distributions might set that definition to 0 by default. In case you get linking errors about standard c++ containers or algorithms when bringing the Exiv2 dependencies with conan, this might indicate a mismatch between the value set in compiler.libcxx and the default values used in your distribution.

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2.2) Visual Studio Notes

I use the following batch file to start cmd.exe. I do this to reduce the complexity of the path which grows as various tools are installed on Windows. The purpose of this script is to ensure a "stripped down path".

@echo off
setlocal
cd  %HOMEPATH%
set "PATH=C:\Python34\;C:\Python27\;C:\Python27\Scripts;C:\Perl64\site\bin;C:\Perl64\bin;C:\WINDOWS\system32;C:\Program Files\Git\cmd;C:\Program Files\Git\usr\bin;c:\Program Files\cmake\bin;"
cmd

Profiles for Visual Studio

Exiv2 v0.27 can be built with VS 2008, 2010, 2012, 2013, 2015 and 2017.

Exiv2 v0.27.1 (and later) can be built with VS 2015, 2017 and 2019. I believe Exiv2 will build with 2013 and earlier, however we don't actively support these version of Visual Studio.

v0.28 is being "modernised" to C++11 and will not support C++98. We don't expect Exiv2 v0.28 to build with VS 2008, 2010, 2012 or 2013.

You create profiles in %HOMEPATH%.conan\profiles with a text editor. For your convenience, you'll find profiles in <exiv2dir>\cmake/msvc\_conan\_profiles. There are 26 in total:

Profile :=    msvc{Edition}{Type}{Bits}
Edition :=  { 2019    | 2017  |  2015  }
Type    :=  { Release | Debug }
Bits    :=  { 64      | 32    }   # 32 bit build is not provided for 2019
Examples:     msvc2019Release msvc2017Release64  msvc2015Debug32

The profile msvc2017Release64 is as follows:

[build_requires]
[settings]
arch=x86_64
build_type=Release
compiler=Visual Studio
compiler.runtime=MD
compiler.version=15
os=Windows
arch_build=x86_64
os_build=Windows
[options]
[env]

Tools for Visual Studio 2019

You will need cmake version 3.14 (and up) and conan 1.14 (and up). Additionally, when I upgraded to conan 1.14.3, I had to manually update (For me: %USERPROFILE% == C:\Users\rmills):

copy/y %USERPROFILE%\.conan\settings.yml.new %USERPROFILE%\.conan\settings.yml

CMake Generators for Visual Studio

In the step-by-step guide, the command $ cmake .. uses the default CMake generator. Always use the generator for your version of Visual Studio. For example:

c:\....\exiv2\build> conan install .. --profile msvc2017Release64 --build missing
c:\....\exiv2\build> cmake         .. -G "Visual Studio 15 2017 Win64"
c:\....\exiv2\build> cmake --build .  --config Release

CMake provides Generators for different editions of Visual Studio. The 64 and 32 bit Generators have different names:

| Architecture | Visual Studio 2019 | Visual Studio 2017 | Visual Studio 2015 | |:--------- |--------------------|--------------------|--------------------|--------------------| | 64 bit | "Visual Studio 16 2019" | "Visual Studio 15 2017 Win64" | "Visual Studio 14 2015 Win64" | | 32 bit | Not provided | "Visual Studio 15 2017" | "Visual Studio 14 2015" |

Recommended settings for Visual Studio

64 bit Release Build

Debug Builds

32bit Builds

Static Builds

The default builds of Exiv2 and sample applications build and use DLLs.

To build static libraries, use the cmake option -DBUILD_SHARED_LIBS=Off. You will probably also want to use the static run-time. The default is to use the dynamic run-time library.

$ cmake -DBUILD_SHARED_LIBS=Off -DEXIV2_ENABLE_DYNAMIC_RUNTIME=Off

If you wish to use the static C run-time library, use the following option in the conan profile.

If you receive a linker warning concerning LIBCMT, it is because you are attempting to link libraries which have been built with different run-time libraries. You should link everything with the dynamic or static run-time. You can link a static library with the dynamic run-time if you wish.

Changing profile settings with the conan command

It is recommended that you use profiles provided in `<exiv2dir>/cmake/msvc_conan_profiles'.

You can modify profile settings on the command line. The following example demonstrates making substantial changes to profile settings by performing a 32 bit build using Visual Studio 2015 with a 2017 profile! This example is not considered good practice, it is an illustration to some conan flexibility which be useful when your build environment is automated.

$ conan install .. --profile msvc2017Release64 -s arch_build=x86 -s arch=x86 -s compiler.version=14
$ cmake         .. -G "Visual Studio 2015"
$ cmake --build .  --config Release

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2.3) Cygwin Notes

Do not use conan on the Cygwin Platform. To build Exiv2 for Cygwin use CMake without conan. We recommend installing dependences (expat, zlib) with platform tools or build/install from source.

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2.4) MinGW Notes

Team Exiv2 supports MinGW msys/2. Team Exiv2 does not support MinGW msys/1.0.

As with Cygwin, we do not recommend using conan to build on the MinGW/msys2 platform. We recommend installing dependences (expat, zlib) with platform tools or build/install from source.

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3 Conan Architecture

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3.1) conanfile.py

In the root level of the Exiv2 repository, the file conanfile.py defines C/C++ dependencies with the syntax: Library/version@user/channel

For example, zlib:

self.requires('self.requires('zlib/1.2.11@conan/stable')')

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3.2) Conan Recipes

Conan searches remote servers for a recipe to build a dependency.

A recipe is a python file which indicates how to build a library from sources. The recipe understands configurations: Platform/Compiler/Settings. If the remote server has a pre-compiled package for your configuration, it will be downloaded. Otherwise, conan will compile the libraries on your machine using instructions in the recipe.

To illustrate, here is list of packages that returned by the command $ conan search

$ conan search --remote conan-center zlib/1.2.11@conan/stable

The output should be:

Existing packages for recipe zlib/1.2.11@conan/stable:

    Package_ID: 0000193ac313953e78a4f8e82528100030ca70ee
        [options]
            shared: False
        [settings]
            arch: x86_64
            build_type: Debug
            compiler: gcc
            compiler.version: 4.9
            os: Linux
        Outdated from recipe: False

    Package_ID: 014be746b283391f79d11e4e8af3154344b58223
        [options]
            shared: False
        [settings]
            arch: x86_64
            build_type: Debug
            compiler: gcc
            compiler.exception: seh
            compiler.threads: posix
            compiler.version: 5
            os: Windows
        Outdated from recipe: False

... deleted ....

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3.3) Conan server search path

Conan searches remote servers for a recipe to build the dependency. You can list them with the command:

$ conan remote list

You can add servers to the conan server search path:

$ conan remote add conan-piponazo https://api.bintray.com/conan/piponazo/piponazo

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3.4) Configuring conan on your machine

Conan stores its configuration and local builds in the directory ~/.conan (%HOMEPATH%\.conan on Windows).

Conan installs several files and two directories:

$HOME/.conan/profiles   Configuration files for compilers/platforms
$HOME/.conan/data       Dependencies are built/stored in this directory

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3.5) Running conan install for the first time

The first time you run $ conan install, it will auto-detect your configuration and store a default profile in the file $HOME/.conan/profiles/default

Normally you will want to define new profiles for choosing different compilers (msvc, gcc, clang), different build_type (Release, Debug), runtimes (MD, MT, MDd, MTd)

The expected output should be something like this, in case it's the first time you run conan:

$ conan install ..  --build missing
Expat/2.2.5@pix4d/stable: Retrieving from predefined remote 'conan-center'
Expat/2.2.5@pix4d/stable: Trying with 'conan-center'...
Downloading conanmanifest.txt
[==================================================] 220B/220B
Downloading conanfile.py
[==================================================] 1.7KB/1.7KB
zlib/1.2.11@conan/stable: Retrieving from predefined remote 'conan-center'
zlib/1.2.11@conan/stable: Trying with 'conan-center'...
Downloading conanmanifest.txt
[==================================================] 121B/121B
Downloading conanfile.py
[==================================================] 5.7KB/5.7KB
libcurl/7.56.1@bincrafters/stable: Retrieving from predefined remote 'bincrafters'
libcurl/7.56.1@bincrafters/stable: Trying with 'bincrafters'...
Downloading conanmanifest.txt
...
PROJECT: Installing D:\Dev\Windows\projects\exiv2\conanfile.py
Requirements
    Expat/2.2.5@pix4d/stable from 'conan-center'
    OpenSSL/1.0.2n@conan/stable from 'conan-center'
    gtest/1.8.0@bincrafters/stable from 'conan-center'
    libcurl/7.56.1@bincrafters/stable from 'bincrafters'
    zlib/1.2.11@conan/stable from 'conan-center'
Packages
    Expat/2.2.5@pix4d/stable:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7
    OpenSSL/1.0.2n@conan/stable:606fdb601e335c2001bdf31d478826b644747077
    gtest/1.8.0@bincrafters/stable:a35f8fa327837a5f1466eaf165e1b6347f6e1e51
    libcurl/7.56.1@bincrafters/stable:e37838f02fd790447943465f1c9317fd1c59b95c
    zlib/1.2.11@conan/stable:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7

PROJECT: Retrieving package 6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7
Expat/2.2.5@pix4d/stable: Looking for package 6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7 in remote 'conan-center'
Downloading conanmanifest.txt
[==================================================] 323B/323B
Downloading conaninfo.txt
[==================================================] 438B/438B
Downloading conan_package.tgz
[==================================================] 133.6KB/133.6KB
Expat/2.2.5@pix4d/stable: Package installed 6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7
PROJECT: Retrieving package a35f8fa327837a5f1466eaf165e1b6347f6e1e51
gtest/1.8.0@bincrafters/stable: Looking for package a35f8fa327837a5f1466eaf165e1b6347f6e1e51 in remote 'conan-center'
Downloading conanmanifest.txt
[==================================================] 3.5KB/3.5KB
Downloading conaninfo.txt
[==================================================] 478B/478B
Downloading conan_package.tgz
[==================================================] 1001.1KB/1001.1KB
gtest/1.8.0@bincrafters/stable: Package installed a35f8fa327837a5f1466eaf165e1b6347f6e1e51
PROJECT: Retrieving package 6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7
...
PROJECT: Generator cmake created conanbuildinfo.cmake
PROJECT: Generator txt created conanbuildinfo.txt
PROJECT: Generated conaninfo.txt
PROJECT imports(): Copied 5 '.dll' files
(conan)

Note that it first downloads the recipes, and then the binary packages. When everything goes well, conan found the recipes in the remotes, and it also found packages for our configuration (msvc2017, Release, MD).

However, if you use other configuration for which there are no packages in the remotes, you will get an error such as:

    PROJECT: WARN: Can't find a 'zlib/1.2.11@conan/stable' package for the specified options and settings:
    - Settings: arch=x86_64, build_type=Release, compiler=clang, compiler.version=3.9, os=Macos
    - Options: shared=False

    ERROR: Missing prebuilt package for 'zlib/1.2.11@conan/stable'
    Try to build it from sources with "--build zlib"
    Or read "http://docs.conan.io/en/latest/faq/troubleshooting.html#error-missing-prebuilt-package"

In that case, we can tell conan to build the library:

$ conan install .. --profile MyEsotericProfile --build missing

Once the command succeeds, we will have the libraries in our system (you can find the recipes and packages in $HOME/.conan/data). When you execute the command conan install with the same profile, the following output is typical:

$ conan install ..
PROJECT: Installing D:\Dev\Windows\projects\exiv2\conanfile.py
Requirements
    Expat/2.2.5@pix4d/stable from 'conan-center'
    OpenSSL/1.0.2n@conan/stable from 'conan-center'
    gtest/1.8.0@bincrafters/stable from 'conan-center'
    libcurl/7.56.1@bincrafters/stable from 'bincrafters'
    zlib/1.2.11@conan/stable from 'conan-center'
Packages
    Expat/2.2.5@pix4d/stable:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7
    OpenSSL/1.0.2n@conan/stable:606fdb601e335c2001bdf31d478826b644747077
    gtest/1.8.0@bincrafters/stable:a35f8fa327837a5f1466eaf165e1b6347f6e1e51
    libcurl/7.56.1@bincrafters/stable:e37838f02fd790447943465f1c9317fd1c59b95c
    zlib/1.2.11@conan/stable:6cc50b139b9c3d27b3e9042d5f5372d327b3a9f7

Expat/2.2.5@pix4d/stable: Already installed!
gtest/1.8.0@bincrafters/stable: Already installed!
zlib/1.2.11@conan/stable: Already installed!
OpenSSL/1.0.2n@conan/stable: Already installed!
libcurl/7.56.1@bincrafters/stable: Already installed!
PROJECT: Generator cmake created conanbuildinfo.cmake
PROJECT: Generator txt created conanbuildinfo.txt
PROJECT: Generated conaninfo.txt
PROJECT imports(): Copied 5 '.dll' files

Indicating that the packages were found in the local cache.

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4 Building Exiv2 with Adobe XMPsdk 2016

With Exiv2 v0.27, you can build Exiv2 with Adobe XMPsdk 2016 on Linux/GCC, Mac/clang and Visual Studio 2017. Other platforms such as Cygwin are not supported by Adobe. Adobe/XMPsdk is built as a external library. Applications which wish use the Adobe XMPsdk directly should build Exiv2 in this configuration and the library can be used by the application and Exiv2. The Adobe XMPsdk can be built as a static or shared library (.DLL)

To build Exiv2 with Adobe XMPsdk 2016, should perform steps 1.1, 1.2 and 1.3 described above, then perform the following:

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4.1) Add a remote directory to conan's recipe search path

By default, conan knows about several public conan repositories. Exiv2 requires the piponazo repository to find the XmpSdk dependency which is not available from conan-center repository.

$ conan remote add conan-piponazo https://api.bintray.com/conan/piponazo/piponazo

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4.2) Build dependencies and install conan artefacts in your build directory

$ conan install .. --options xmp=True --build missing

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4.3) Execute cmake to generate build files for your environment:

You must tell CMake to link Adobe's library:

$ cmake .. -DEXIV2_ENABLE_EXTERNAL_XMP=On # -G "Visual Studio 15 2017 Win64" -DCMAKE_BUILD_TYPE=Release

MacOS-X users should use the cmake Xcode Generator

$ cmake .. -DEXIV2_ENABLE_EXTERNAL_XMP=On -G Xcode

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4.4) Build Exiv2 and link Adobe XMPsdk library

$ cmake --build . --config Release

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5 Webready Support

Exiv2 can perform I/O using internet protocols such as https, https, ftp and ssh.

The feature is disabled by default. You will need to instruct conan to build/download necessary libraries (curl, openssl and libssh) and tell CMake to link to the libraries.

$ conan install .. --options webready=True
$ cmake -DEXIV2_ENABLE_WEBREADY=ON -DEXIV2_ENABLE_CURL=ON -DEXIV2_ENABLE_SSH=ON ..

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Written by Robin Mills
robin@clanmills.com
Updated: 2019-04-18