The file ReadMe.txt in a build bundle describes how to install the library on the platform. ReadMe.txt also documents how to compile and link code on the platform.
This will install the library into the "standard locations". The library will be installed in `/usr/local/lib`, executables (including the exiv2 command-line program) in `/usr/local/bin/` and header files in `/usr/local/include/exiv2`
cmake generates files in the build directory. cmake generates the project/solution/makefiles required to build the exiv2 library and sample applications. cmake also creates the files exv\_conf.h and exiv2lib\_export which contain compiler directives about the build options you have chosen and the availability of libraries on your machine.
We recommend that you use conan to download the Exiv2 external dependencies on Windows. On other platforms (maxOS, Ubuntu and others), you should use the platform package manger. These are discussed: [Platform Notes](#5) The options to configure and compile the project using Visual Studio are similar to UNIX like systems.
See [README-CONAN](README-CONAN.md) for more information about Conan.
| CMAKE\_INSTALL\_PREFIX<br/>CMAKE\_BUILD\_TYPE<br/>BUILD\_SHARED\_LIBS | Where to install on your computer _**(/usr/local)**_<br/>Type of build _**(Release)**_ See: [Debugging Exiv2](#2-11) <br/>Build exiv2lib as shared or static _**(On)**_ |
| PNG image support | zlib | ON | -DEXIV2\_ENABLE\_PNG=Off | [http://zlib.net/](http://zlib.net/) |
| XMP support | expat | ON | -DEXIV2\_ENABLE\_XMP=Off | [http://expat.sourceforge.net](http://expat.sourceforge.net)/<br/>Use _**Expat 2.2.6**_ and later |
| Natural language system | gettext | OFF | -DEXIV2\_ENABLE\_NLS=On | [http://www.gnu.org/software/gettext/](http://www.gnu.org/software/gettext/) |
| Character set conversion | libiconv | | Disabled for Visual Studio.<br>Linked when installed on UNIX like platforms. | [https://www.gnu.org/software/libiconv/](https://www.gnu.org/software/libiconv/) |
development package of a dependency to install the header files and libraries required to build Exiv2. The script
`ci/install_dependencies.sh` is used to setup CI images on which we build and test Exiv2 on many platforms when we modify code. You may find that helpful in setting up your platform dependencies.
The library libiconv is used to perform character set encoding in the tags Exif.Photo.UserComment, Exif.GPSInfo.GPSProcessingMethod and Exif.GPSInfo.GPSAreaInformation. This is documented in the exiv2 man page.
CMake will detect libiconv of all UNIX like systems including Linux, macOS, UNIX, Cygwin64 and MinGW/msys2. If you have installed libiconv on your machine, Exiv2 will link and use it.
The library libiconv is a GNU library and we do not recommend using libiconv with Exiv2 when building with Visual Studio.
Exiv2 includes the file cmake/FindIconv.cmake which contains a guard to prevent CMake from finding libiconv when you build with Visual Studio. This was added because of issues reported when Visual Studio attempted to link libconv libraries installed by Cygwin, or MinGW or gnuwin32. [https://github.com/Exiv2/exiv2/issues/1250](https://github.com/Exiv2/exiv2/issues/1250)
There are build instructions about Visual Studio in libiconv-1.16/INSTALL.window require you to install Cygwin. There is an article here about building libiconv with Visual Studio. [https://www.codeproject.com/Articles/302012/How-to-Build-libiconv-with-Microsoft-Visual-Studio](https://www.codeproject.com/Articles/302012/How-to-Build-libiconv-with-Microsoft-Visual-Studio).
If you wish to use libiconv with Visual Studio you will have to build libiconv and remove the "guard" in cmake/FindIconv.cmake. Team Exiv2 will not provide support concerning libiconv and Visual Studio.
When exiv2 is installed, the file exiv2.pc used by pkg-config is installed in `${CMAKE_INSTALL_PREFIX}/lib/pkgconfig` You will need to set the following in your environment:
To build localisation support, use the CMake option `-DEXIV2_ENABLE_NLS=On`. You must install the `gettext` package with your package manager or from source. The `gettext` package is available from [http://www.gnu.org/software/gettext/](http://www.gnu.org/software/gettext/) and includes the library `libintl` and utilities to build localisation files. If CMake produces error messages which mention libintl or gettext, you should verify that the package `gettext` has been correctly built and installed.
You must install the build to test localisation. This ensures that the localisation message files can be found at run-time. You cannot test localisation in the directory `build\bin`.
Those blocks of code are not compiled unless you define `EXIV2_DEBUG_MESSAGES`. They are provided for additional debugging information. For example, if you are interested in additional output from webpimage.cpp, you can update your build as follows:
If you are debugging library code, it is recommended that you use the exiv2 command-line program as your test harness as Team Exiv2 is very familiar with this tool and able to give support.
4) Using Debugger IDEs such as Xcode, CLion, Visual Studio, Eclipse or QtCreator
I have used all those IDEs to debug the Exiv2 library and applications. All of them work. You may find it takes initial effort, however I assure you that they all work well.
I personally use CLion which has excellent integration with CMake. It will automatically add **`-DCMAKE_BUILD_TYPE=Debug`** to the cmake command. It keeps build types in separate directories such as **`<exiv2dir>/cmake-build-debug`**.
[TOC](#TOC)
5) cmake --build . options **`--config Release|Debug`** and **`--target install`**
Visual Studio and Xcode can build debug or release builds without using the option **`-DCMAKE_BUILD_TYPE`** because the generated project files can build multiple types. The option **`--config Debug`** can be specified on the cmake command-line to specify the build type. Alternatively, if you prefer to build in the IDE, the UI provides options to select the configuration and target.
To speed up compilation, the utility ccache can be installed to cache the output of the compiler. This greatly speeds up the build when you frequently built code that has not been modified.
Installing and using ccache (and other similar utilities), is platform dependent. On Ubuntu:
```bash
$ sudo apt install --yes ccache
```
To build with ccache, use the cmake option **-DBUILD\_WITH\_CCACHE=On**
Due to the way in which ccache is installed in Fedora (and other Linux distros), ccache effectively replaces the compiler. A default build or **-DBUILD\_WITH\_CCACHE=Off** is not effective and the environment variable CCACHE_DISABLE is required to disable ccache. [https://github.com/Exiv2/exiv2/issues/361](https://github.com/Exiv2/exiv2/issues/361)
Exiv2 heavily relies on standard C++ containers. Static or global variables are used read-only, with the exception of the XMP namespace registration function (see below). Thus Exiv2 is thread safe in the same sense as C++ containers:
Different instances of the same class can safely be used concurrently in multiple threads.
In order to use the same instance of a class concurrently in multiple threads the application must serialize all write access to the object.
The level of thread safety within Exiv2 varies depending on the type of metadata: The Exif and IPTC code is reentrant. The XMP code uses the Adobe XMP toolkit (XMP SDK), which according to its documentation is thread-safe. It actually uses mutexes to serialize critical sections. However, the XMP SDK initialisation function is not mutex protected, thus Exiv2::XmpParser::initialize is not thread-safe. In addition, Exiv2::XmpProperties::registerNs writes to a static class variable, and is also not thread-safe.
Therefore, multi-threaded applications need to ensure that these two XMP functions are serialized, e.g., by calling them from an initialization section which is run before any threads are started. All exiv2 sample applications begin with:
As discussed in the section on Thread Safety, Exiv2 classes for Exif and IPTC metadata are fully reentrant and require no initialisation or cleanup.
Adobe's XMPsdk is generally thread-safe, however it has to be initialized and terminated before and after starting any threads to access XMP metadata. The Exiv2 library will initialize this if necessary, however it does not terminate the XMPsdk.
You can cross compile Exiv2 on Linux for MinGW. We have used the following method on **Fedora** and believe this is also possible on Ubuntu and other distros. Detailed instructions are provided here for **Fedora**.
You will need to install x86_64 libraries to support the options you wish to use. By default, you will need libz and expat. Your `dnf` command above has installed them for you. If you wish to use features such as `webready` you should install openssl and libcurl as follows:
Note, you may wish to choose to build with optional features and/or build static libraries. To do this, request appropriately on the mingw64-cmake command:
On a default wine installation, you are in the MSDOS/cmd.exe prompt. You cannot execute the exiv2 test suite in this environment as you require python3 and MSYS/bash to run the suite.
Exiv2 uses the default compiler for your system. Exiv2 v0.27 was written to the C++ 1998 standard and uses auto\_ptr. The C++11 and C++14 compilers will issue deprecation warnings about auto\_ptr. As _auto\_ptr support has been removed from C++17, you cannot build Exiv2 v0.27 with C++17 or later compilers._ Exiv2 v0.28 and later do not use auto\_ptr and will build with all modern C++ Standard Compilers.
The option -DCMAKE\_CXX\_FLAGS=-Wno-deprecated suppresses warnings from C++11 concerning auto\_ptr. The compiler will issue deprecation warnings about video, eps and ssh code in Exiv2 v0.27. This is intentional. These features of Exiv2 will not be available in Exiv2 v0.28.
**Caution:** Visual Studio users should not use -DCMAKE\_CXX\_FLAGS=-Wno-deprecated.
You can build either static or shared libraries. Both can be linked with either static or shared run-time libraries. You specify the shared/static with the option `-BUILD_SHARED_LIBS=On|Off` You specify the run-time with the option `-DEXIV2_ENABLE_DYNAMIC_RUNTIME=On|Off`. The default for both options default is On. So you build shared and use the shared libraries which are `.dll` on Windows (msvc, Cygwin and MinGW/msys), `.dylib` on macOS and `.so` on Linux and UNIX.
CMake creates your build artefacts in the directories `bin` and `lib`. The `bin` directory contains your executables and .dlls. The `lib` directory contains your static libraries. When you install exiv2, the build artefacts are copied to your system's prefix directory which by default is `/usr/local/`. If you wish to test and use your build without installing, you will have to set you PATH appropriately. Linux/Unix users should also set `LD_LIBRARY_PATH` and macOS users should set `DYLD_LIBRARY_PATH`.
The default build is SHARED/DYNAMIC and this arrangement treats all executables and shared libraries in a uniform manner.
**Caution:** _The following discussion only applies if you are linking to a static version of the exiv2 library._ You may get the following error from CMake:
```bash
CMake Error at src/CMakeLists.txt:30 (add_library):
Target "my-app-or-library" links to target "Iconv::Iconv" but the target was
not found. Perhaps a find_package() call is missing for an IMPORTED
target, or an ALIAS target is missing?
```
Be aware that the warning concerning `src/CMakeLists.txt:30 (add_library)` refers to your file src/CMakeLists.txt. Although exiv2 has statically linked `Iconv()`, your code also needs to link. You achieve that in your src/CMakeLists.txt with the code:
**Attention is drawn to the possibility that bmff support may be the subject of patent rights. _Exiv2 shall not be held responsible for identifying any or all such patent rights. Exiv2 shall not be held responsible for the legal consequences of the use of this code_.**
Access to the bmff code is guarded in two ways. Firstly, you have to build the library with the cmake option: `-DEXIV2_ENABLE_BMFF=On`. Secondly, the application must enable bmff support at run-time by calling the following function.
Applications may wish the provide a preference setting to enable bmff support and thereby place the responsibility for the use of this code with the user of the application.
It is recommended that you enclose the call to `enableBMFF()` with the compile time macro EXIV2\_TEST\_VERSION to ensure that your code builds cleanly on earlier versions of Exiv2. It is recommended that you call enableBMFF() at process start-up as it is not threadsafe. A code snippet is provided in [2.14 Thread Safety](#2-14).
_**Caution: Visual Studio Users using cmd.exe**_<br>_You may use MinGW/msys2 `make` to to execute tests in the test directory. To execute tests from the build directory, use `cmake`. This is discussed in detail below: [Running tests on Visual Studio builds](#4-2)_
The Variable EXIV2\_PORT or EXIV2\_HTTP can be set to None to skip http tests. The http server is started with the command `python3 -m http.server $port`. On Windows, you will need to run this manually _**once**_ to authorise the firewall to permit python to use the port.
You can run individual tests in the `test` directory. **Caution:** If you build in a directory other than \<exiv2dir\>/build, you must set EXIV2\_BINDIR to run tests from the `test` directory.
To run the bash scripts you will need to install MinGW/msys2 which provides you with the bash interpreter. You can run the test suite from bash, or from cmd.exe.
**Caution:** To run the python tests, _You will need a DOS python3 interpreter which must be called python3.exe. I copied the python.exe program:_ You may have to modify the PATH to ensure that the DOS python3 is used. You may have to modify the PATH to access MinGW/msys2 tools such as bash and make. Be careful to ensure the DOS python3.exe is found before the MinGW/msys2 python3.
For users of other platforms, the script <exiv2dir>/ci/install_dependencies.sh has code used to configure many platforms. The code in that file is a useful guide to configuring your platform.
The exiv2 command-line program provides an option **`--grep`** to filter output. The implementation requires the header file **`<regex.h>`** and supporting library to be available during the build. When not available, the option **`--grep`** degrades to a substring match. Because there are several versions of **`<regex.h>`** available on the MinGW platform, detection of regex is always disabled on this platform and uses substring match. The following command reveals if regex is included in your build:
We recommend that you use Conan to build Exiv2 using Visual Studio. Exiv2 v0.27 can be built with Visual Studio versions 2008 and later. We actively support and build with Visual Studio 2015, 2017 and 2019.
I use the following batch file `cmd64.bat` to start cmd.exe. I do this to reduce the complexity of the path which grows as various tools are installed on Windows. As well as providing a "stripped down path", it also ensures the DOS python3 and DOS bash are on the path.
Exiv2 can be built on many Unix and Linux distros. With v0.27.2, we are starting to actively support the Unix Distributions NetBSD and FreeBSD. For v0.27.3, I have added support for Solaris 11.4
We do not have CI support for these platforms on GitHub. However, I regularly build and test them on my MacMini Buildserver. The device is private and not on the internet.
I have provided notes here based on my experience with these platforms. Feedback is welcome. I am willing to support Exiv2 on other commercial Unix distributions such as AIX, HP-UX and OSF/1 if you provide with an ssh account for your platform. I will require super-user privileges to install software.
For all platforms you will need the following components to build:
Clang is pre-installed as ``/usr/bin/{cc|c++}` as well as libz and expat. FreeBSD uses pkg as the package manager which I used to install cmake and git.
**Caution**: _The package manager *pkg* is no longer working on FreeBSD 12.0. I will move to 12.1 for future work. Others have reported this issue on 12.1. Broken package manager is very bad news. There are other package managers (such as ports), however installing and getting it to work is formidable._
