exiv2/README-CMAKE.md

# CMake in Exiv2

CMake is a cross-platform build system, to control the
compilation process using platform/compiler independent configuration files.

STATUS:

* CMake scripts are functional and used to perform the daily build on the buildserver
  for MacOS-X, Cygwin, Linux and Visual Studio (2005, 8, 10, 12, 13, 15 and 17)

* Team Exiv2 no longer provide support for MinGW (with/without CMake)
  Exiv2 is very difficult to build on MinGW with CMake.
  This is discussed in TODO-CMAKE

Latest update: 2018-09-12

## 1 CMake resources

You have to install [cmake](http://www.cmake.org/) on your target system. The minimum version required is 3.3.2.

There are some global CMake options that you can use in Exiv2 :

- `CMAKE_INSTALL_PREFIX` : decide where the program will be install on your computer.
- `CMAKE_BUILD_TYPE` : decide which type of build you want.
- `BUILD_SHARED_LIBS` : To control whether you want to build exiv2lib as shared or static.

More information about Exiv2 CMake options in CMakeLists.txt

## 2 Building and Installing on UNIX-like systems

This process covers MacOS-X, Linux and Cygwin.

Run the following commands from the top directory (containing this
file) to configure, build and install the library and utilities:

    $ mkdir build && cd build
    $ cmake .. or cmake-gui ..
    $ make -j
    $ (sudo) make install

Note that the CMake generator used by default on Unix is : 'Makefiles'. However you can chose others like 'Ninja'

To uninstall Exiv2, run:

    $ (sudo) make uninstall

## 3 Building and installing for Visual Studio Users

exiv2 provides two build environment for users of Visual Studio:

cmake:    This environment
msvc:     32 bit AND 64 bit build environment for MSVC 2005 and later (2005/2008/10/12/13/15/17)

Please note that CMake doesn't build code. It generates build environments.
CMake is a language for describing builds and the CMake interpreter generates
the build environment for your system.

CMake generates MSVC .sln and .vcproj files for your target environment.
The files generated by CMake provide 4 configs: Debug|Release|RelWithDebInfo|MinSizeRel
The current architecture of CMake requires you to decide before running cmake:
1)  The version of DevStudio
2)  32bit or 64 bit builds
3)  Building static or shared libraries

We have three contributed CMake Build Environments:

### a) contrib/cmake/msvc
  The following command will build Exiv2 and dependencies:

  c:\exiv2dir\contrib\cmake\msvc> cmd /c "vcvars 2017 64 && cmakeBuild --build --samples"

  Please read contrib/cmake/msvc/ReadMe.txt for more information.

### b) contrib/build/msvc

  The scripts require:
  - Cygwin (in order to download all dependencies (zlib, expat, ssl, curl, ssh), including exiv2 trunk from svn)
  - CMake
  - SVN (optional)

  Then
   - put the two scripts (build.cmd and setenv.cmd) into a completely empty directory
   - adapt the paths in setenv.cmd
   - open the VS command line shell
   - execute build.cmd (if there are any errors, the script should tell you)

  Exiv2 should be packaged in the dist directory with all the .lib, include and binary files you need.

### c) Running CMake commands manually from command line

  From Exiv2 0.26.0 to 0.26.1 the CMake code of the project was rewritten and now it is possible to configure
  project from the command line as we do in the Unix sytems. As in the UNIX case, we can run the following
  commands from the top directory to configure, build and install the library and utilities:

    $ mkdir build && cd build
    $ cmake .. or cmake-gui ..
    $ make -j
    $ make install

  However there are some particularities on Windows that might cause the CMake command does not find
  the compiler correctly.

  Previous versions of Visual Studio were creating an environment variable (VSCOMNTOOLS140, for example) that
  points at the compiler and other resources relevant to that version of the compiler. However in Visual Studio
  2017, they do not do that anymore.

  We recommend to call the `vcvarsall.bat` Visual Studio configuration script before running CMake.
  This script will setup some environment variables that will enable CMake to find the compiler,
  include directories, libraries, etc. For example, with Visual Studio 2017 installed on your system, you will need to run:

```bash
  c:\exiv2dir> call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat"
```

  It is also important to note that the default CMake configuration assumes the existence of some libraries
  in your system. If they are not available, the configuration will fail. It is possible to disable some
  features, or provide the paths to the INCLUDE folders, or libraries, at the moment of calling CMake the
  first time.

  In this example, we disable the NLS and PNG support, and we specify the path where we have the EXPAT library:
  ```bash
  c:\exiv2dir> cmake -DEXIV2_ENABLE_NLS=OFF -DEXIV2_ENABLE_PNG=OFF -DCMAKE_PREFIX_PATH="C:\pathToExpat\ ../
  ```

#### CMake Generators

  It is also important to note that the default CMake generator is 'Visual Studio' (The version will depend
  on the vcvarsall.bat script called before running CMake).

  If you are not a big fan of Visual Studio you can use other generators like: 'Ninja'. In order to use them
  you just need to pass the option -GNinja at the moment of calling CMake for the first time:

```bash
  $ cmake -GNinja -DEXIV2_ENABLE_NLS=OFF -DEXIV2_ENABLE_PNG=OFF -DCMAKE_PREFIX_PATH="C:\pathToExpat\ ../
```

  Note: For using the Ninja generator you will need to have the ninja build system executable in your
  $PATH. More info at https://ninja-build.org/.

## 4 Building and installing for MinGW Users

CMake/MinGW has a number of serious issues.  This will be reported to Kitware.

It is possible to use CMake/MinGW if you put in some effort.  This is documented in TODO-CMAKE.

## 5 Using conan to get the exiv2 project dependencies

In README-CONAN.md we give explanations about how to use conan to get all the Exiv2 dependencies.
Basically, all you need to do is to have conan installed on your system and run the command
`conan install` before calling CMake:

    $ mkdir build && cd build
    $ conan install ..
    $ cmake .. or cmake-gui ..

## 6 Consuming Exiv2 with CMake

When installing exiv2 by running the **install** target we get some files under the folder
`${CMAKE_INSTALL_PREFIX}/share/exiv2/cmake/`.

In the example project https://github.com/piponazo/exiv2Consumer you could see how to consume
exiv2 via CMake by using these files.

## 7 Using CPack in Exiv2

CPack is a tool that comes with CMake that is used to generate package installers or tarballs.

### Packaging the binaries

Once you have created a build folder, and configured and compiled the project, you just need to run a
command to generate a package:

```bash
# Previous steps: create build directory, configure and compile the project
$ cd exiv2
$ mkdir build && cd build
$ cmake ..
$ cmake --build . --config Release

# How to generate a package with cpack (With tarbz2)
$ cpack -G TBZ2 .
CPack: Create package using TBZ2
CPack: Install projects
CPack: - Run preinstall target for: exiv2
CPack: - Install project: exiv2
CPack: Create package
CPack: - package: /path/to/exiv2/build/exiv2-0.27.0-Linux.tar.bz2 generated.
```
You can obtain a complete list of the different generators by running `cpack -h`.

### Packaging the sources

CPack is also convenient for generating a tarball with the sources of the project. Since we included CPack in
our CMake code, a new target `package_source` is provided which creates such tarball automatically:

```bash
$ make package_source
Run CPack packaging tool for source...
CPack: Create package using TBZ2
CPack: Install projects
CPack: - Install directory: /media/linuxDev/programming/exiv2
CPack: Create package
CPack: - package: /media/linuxDev/programming/exiv2/build/exiv2-0.27.0-Source.tar.bz2 generated.
```

Note that you can also run `cmake --build . --config Release --target package_source` in case you are not using
the "UNIX Makefiles" Generator.