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\_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/) |
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` by yourself. 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 as your test harness as Team Exiv2 is very familiar with this tool and able to give support.
[TOC](#TOC)
3) Starting the debugger
This is platform specific. On Linux:
```bash
$ gdb exiv2
```
[TOC](#TOC)
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 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.
With the Unix Makefile generator, the targets can be listed:
```bash
$ make help
The following are some of the valid targets for this Makefile:
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.
[TOC](#TOC)
<divid="2-15">
### 2.15 Library Initialisation and Cleanup
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.
The Exiv2 command-line and the sample applications call the following at the outset:
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**.
$ sudo dnf install mingw64-gcc-c++ mingw64-filesystem mingw64-expat mingw64-zlib cmake make
```
####2 Install Dependancies
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:
If you have not installed wine, Fedora will offer to install it for you.
####6 Running the test suite
On a default wine installation, you are in the MSDOS/cmd prompt. You cannot execute the exiv2 test suite in this environment as you require python3 and MSYS/bash to run the suite.
You should mount the your Fedora exiv2/ directory on a Windows machine on which you have installed MSYS2. You will need python3 and make.
My build machines is a MacMini with VMs for Windows, Fedora and other platforms. On Fedora, I build in a Mac directory which is shared to all VMs.
```bash
[rmills@rmillsmm-fedora 0.27-maintenance]$ pwd
/media/psf/Home/gnu/github/exiv2/0.27-maintenance
[rmills@rmillsmm-fedora 0.27-maintenance]$ ls -l build_mingw_fedora/bin/exiv2.exe
You can run individual tests in the `test` directory using the environment variable EXIV2\_BINDIR to specify the location of the build artifacts. For Windows builds (msvc, Cygwin, Msys, MinGW), set EXIV2_EXT=.exe
Use the bash interpreter for MinGW/msys2 to run the test suite. It's essential to have a DOS Python3 interpreter on your path called `python3.exe` The variables EXIV2\_BINDIR and EXIV2\_EXT enable the test suite to locate the MSVC build artifacts.
$ for i in base-devel git cmake coreutils python3 man gcc gdb make dos2unix diffutils zlib-devel libexpat-devel libiconv-devel gettext-devel; do (echo y|pacman -S $i); done
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:
Download and build libiconv-1.15: [https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.15.tar.gz](https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.15.tar.gz)
We recommend that you use Conan to build Exiv2 using Microsoft Visual C++. 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 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".
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.
**Caution:** _There are issues with the bash test suite on UNIX as the utility `diff` has different command syntax. While most of the test suite operates successfully, several tests require more investigation. I am confident that this issues are in the test suite and not in exiv2.__
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._
