libtorrent manual
| Author: | Arvid Norberg, arvid@rasterbar.com |
|---|
Table of contents
downloading and building
To acquire the latest version of libtorrent, you'll have to grab it from SVN. You'll find instructions on how to do this here (see subversion access).
The build systems supported "out of the box" in libtorrent are boost-build v2 (BBv2) and autotools (for unix-like systems). If you still can't build after following these instructions, you can usually get help in the #libtorrent IRC channel on irc.freenode.net.
Community contributed build tutorials can be found on the wiki.
Warning
A common mistake when building and linking against libtorrent is to build with one set of configuration options (#defines) and link against it using a different set of configuration options. Since libtorrent has some code in header files, that code will not be compatible with the built library if they see different configurations.
Always make sure that the same TORRENT_* macros are defined when you link against libtorrent as when you build it.
Boost-build supports propagating configuration options to dependencies. When building using the makefiles, this is handled by setting the configuration options in the pkg-config file. Always use pkg-config when linking against libtorrent.
building from svn
To build libtorrent from svn you need to check out the libtorrent sources from sourceforge and also check out the asio sources from its sourceforge cvs. If you downloaded a release tarball, you can skip this section.
To prepare the directory structure for building, follow these steps:
- Check out libtorrent (instructions).
- Check out asio (instructions).
- Copy the asio/include/asio/ directory into the libtorrent/include/libtorrent/ directory. Alternatively you can make a symbolic link.
- Copy asio/include/asio.hpp into libtorrent/include/libtorrent.
Now the libtorrent directory is ready for building. Follow the steps in one of the following sections depending on which build system you prefer to use.
building with BBv2
The primary reason to use boost-build is that it will automatically build the dependent boost libraries with the correct compiler settings, in order to ensure that the build targets are link compatible (see boost guidelines for some details on this issue).
Since BBv2 will build the boost libraries for you, you need the full boost source package. Having boost installed via some package system is usually not enough (and even if it is enough, the necessary environment variables are usually not set by the package installer).
If you want to build against an installed copy of boost, you can skip directly to step 3 (assuming you also have boost build installed).
Step 1: Download boost
You'll find boost here.
Extract the archive to some directory where you want it. For the sake of this guide, let's assume you extract the package to c:\boost_1_34_0 (I'm using a windows path in this example since if you're on linux/unix you're more likely to use the autotools). You'll need at least version 1.34 of the boost library in order to build libtorrent.
Step 2: Setup BBv2
First you need to build bjam. You do this by opening a terminal (In windows, run cmd). Change directory to c:\boost_1_34_0\tools\jam\src. Then run the script called build.bat or build.sh on a unix system. This will build bjam and place it in a directory starting with bin. and then have the name of your platform. Copy the bjam.exe (or bjam on a unix system) to a place that's in you shell's PATH. On linux systems a place commonly used may be /usr/local/bin or on windows c:\windows (you can also add directories to the search paths by modifying the environment variable called PATH).
Now you have bjam installed. bjam can be considered an interpreter that the boost-build system is implemented on. So boost-build uses bjam. So, to complete the installation you need to make two more things. You need to set the environment variable BOOST_BUILD_PATH. This is the path that tells bjam where it can find boost-build, your configuration file and all the toolsets (descriptions used by boost-build to know how to use different compilers on different platforms). Assuming the boost install path above, set it to c:\boost_1_34_0\tools\build\v2.
To set an environment variable in windows, type for example:
set BOOST_BUILD_PATH=c:\boost_1_34_0\tools\build\v2
In a terminal window.
The last thing to do to complete the setup of BBv2 is to modify your user-config.jam file. It is located in c:\boost_1_34_0\tools\build\v2. Depending on your platform and which compiler you're using, you should add a line for each compiler and compiler version you have installed on your system that you want to be able to use with BBv2. For example, if you're using Microsoft Visual Studio 7.1 (2003), just add a line:
using msvc : 7.1 ;
If you use GCC, add the line:
using gcc ;
If you have more than one version of GCC installed, you can add the commandline used to invoke g++ after the version number, like this:
using gcc : 3.3 : g++-3.3 ; using gcc : 4.0 : g++-4.0 ;
Another toolset worth mentioning is the darwin toolset (For MacOS X). From Tiger (10.4) MacOS X comes with both GCC 3.3 and GCC 4.0. Then you can use the following toolsets:
using darwin : 3.3 : g++-3.3 ; using darwin : 4.0 : g++-4.0 ;
Note that the spaces around the semi-colons and colons are important!
Also see the official installation instructions.
Step 3: Building libtorrent
When building libtorrent, the Jamfile expects the environment variable BOOST_ROOT to be set to the boost installation directory. It uses this to find the boost libraries it depends on, so they can be built and their headers files found. So, set this to c:\boost_1_34_0. You only need this if you're building against a source distribution of boost.
Then the only thing left is simply to invoke bjam. If you want to specify a specific toolset to use (compiler) you can just add that to the commandline. For example:
bjam msvc-7.1 boost=source bjam gcc-3.3 boost=source bjam darwin-4.0 boost=source
If you're building against a system installed boost, specify boost=system.
To build different versions you can also just add the name of the build variant. Some default build variants in BBv2 are release, debug, profile.
You can build libtorrent as a dll too, by typing link=shared, or link=static to build a static library.
If you want to explicitly say how to link against the runtime library, you can set the runtime-link feature on the commandline, either to shared or static. Most operating systems will only allow linking shared against the runtime, but on windows you can do both. Example:
bjam msvc-7.1 link=static runtime-link=static boost=source
Warning
If you link statically to the runtime library, you cannot build libtorrent as a shared library (DLL), since you will get separate heaps in the library and in the client application. It will result in crashes and possibly link errors.
Warning
With boost-build V2 (Milestone 11), the darwin toolset uses the -s linker option to strip debug symbols. This option is buggy in Apple's GCC, and will make the executable crash on startup. On Mac OS X, instead build your release executables with the debug-symbols=on option, and later strip your executable with strip.
Warning
Some linux systems requires linking against librt in order to access the POSIX clock functions. If you get an error complaining about a missing symbol clock_gettime, you have to give need-librt=yes on the bjam command line. This will make libtorrent link against librt.
Note
When building on Solaris, you might have to specify stdlib=sun-stlport on the bjam command line.
The build targets are put in a directory called bin, and under it they are sorted in directories depending on the toolset and build variant used.
To build the examples, just change directory to the examples directory and invoke bjam from there. To build and run the tests, go to the test directory and run bjam.
Note that if you're building on windows using the msvc toolset, you cannot run it from a cygwin terminal, you'll have to run it from a cmd terminal. The same goes for cygwin, if you're building with gcc in cygwin you'll have to run it from a cygwin terminal. Also, make sure the paths are correct in the different environments. In cygwin, the paths (BOOST_BUILD_PATH and BOOST_ROOT) should be in the typical unix-format (e.g. /cygdrive/c/boost_1_34_0). In the windows environment, they should have the typical windows format (c:/boost_1_34_0).
The Jamfile will define NDEBUG when it's building a release build. For more build configuration flags see Build configurations.
Build features:
| boost build feature | values |
|---|---|
| boost |
|
| boost-link |
|
| logging |
|
| dht-support |
|
| need-librt |
|
| zlib |
|
| geoip | |
| upnp-logging |
|
| openssl |
|
| pool-allocators |
|
| link |
|
| runtime-link |
|
| variant |
|
| character-set | This setting will only have an affect on windows. Other platforms are expected to support UTF-8.
|
| invariant-checks | This setting only affects debug builds (where NDEBUG is not defined). It defaults to on.
|
| debug-symbols |
|
| deprecated-functions |
|
The variant feature is implicit, which means you don't need to specify the name of the feature, just the value.
The logs created when building vlog or log mode are put in a directory called libtorrent_logs in the current working directory.
When building the example client on windows, you need to build with link=static otherwise you may get unresolved external symbols for some boost.program-options symbols.
For more information, see the Boost build v2 documentation, or more specifically the section on builtin features.
building with autotools
First of all, you need to install automake and autoconf. Many unix/linux systems comes with these preinstalled.
The prerequisites for building libtorrent are boost.thread, boost.date_time and boost.filesystem. Those are the compiled boost libraries needed. The headers-only libraries needed include (but is not necessarily limited to) boost.bind, boost.ref, boost.multi_index, boost.optional, boost.lexical_cast, boost.integer, boost.iterator, boost.tuple, boost.array, boost.function, boost.smart_ptr, boost.preprocessor, boost.static_assert.
If you want to build the client_test example, you'll also need boost.regex and boost.program_options.
Step 1: Generating the build system
No build system is present if libtorrent is checked out from CVS - it needs to be generated first. If you're building from a released tarball, you may skip directly to Step 2: Running configure.
Execute the following commands, in the given order, to generate the build system:
aclocal -I m4 autoheader libtoolize --copy --force automake --add-missing --copy --gnu autoconf
On darwin/OSX you have to run glibtoolize instead of libtoolize.
Step 2: Running configure
In your shell, change directory to the libtorrent directory and run ./configure. This will look for libraries and C++ features that libtorrent is dependent on. If something is missing or can't be found it will print an error telling you what failed.
The most likely problem you may encounter is that the configure script won't find the boost libraries. Make sure you have boost installed on your system. The easiest way to install boost is usually to use the preferred package system on your platform. Usually libraries and headers are installed in standard directories where the compiler will find them, but sometimes that may not be the case. For example when installing boost on darwin using darwinports (the package system based on BSD ports) all libraries are installed to /opt/local/lib and headers are installed to /opt/local/include. By default the compiler will not look in these directories. You have to set the enviornment variables LDFLAGS and CXXFLAGS in order to make the compiler find those libs. In this example you'd set them like this:
export LDFLAGS=-L/opt/local/lib export CXXFLAGS=-I/opt/local/include
It was observed on FreeBSD (release 6.0) that one needs to add '-lpthread' to LDFLAGS, as Boost::Thread detection will fail without it, even if Boost::Thread is installed.
If you need to set these variables, it may be a good idea to add those lines to your ~/.profile or ~/.tcshrc depending on your shell.
If the boost libraries are named with a suffix on your platform, you may use the --with-boost-thread= option to specify the suffix used for the thread library in this case. For more information about these options, run:
./configure --help
On gentoo the boost libraries that are built with multi-threading support have the suffix mt.
You know that the boost libraries were found if you see the following output from the configure script:
checking whether the Boost::DateTime library is available... yes checking for main in -lboost_date_time... yes checking whether the Boost::Filesystem library is available... yes checking for main in -lboost_filesystem... yes checking whether the Boost::Thread library is available... yes checking for main in -lboost_thread... yes
Another possible source of problems may be if the path to your libtorrent directory contains spaces. Make sure you either rename the directories with spaces in their names to remove the spaces or move the libtorrent directory.
Creating a debug build
To tell configure to build a debug version (with debug info, asserts and invariant checks enabled), you have to run the configure script with the following option:
./configure --enable-debug=yes
Creating a release build
To tell the configure to build a release version (without debug info, asserts and invariant checks), you have to run the configure script with the following option:
./configure --enable-debug=no
The above option make use of -DNDEBUG, which is used throughout libtorrent.
Step 3: Building libtorrent
Once the configure script is run successfully, you just type make and libtorrent, the examples and the tests will be built.
When libtorrent is built it may be a good idea to run the tests, you do this by running make check.
If you want to build a release version (without debug info, asserts and invariant checks), you have to rerun the configure script and rebuild, like this:
./configure --disable-debug make clean make
building with other build systems
If you're making your own project file, note that there are two versions of the file abstraction. There's one file_win.cpp which relies on windows file API that supports files larger than 2 Gigabytes. This does not work in vc6 for some reason, possibly because it may require windows NT and above. The other file, file.cpp is the default implementation that simply relies on the standard low level io routines (read(), write(), open() etc.), this implementation doesn't do anything special to support unicode filenames, so if your target is Windows 2000 and up, you may want to use file_win.cpp which supports unicode filenames.
If you're building in MS Visual Studio, you may have to set the compiler options "force conformance in for loop scope", "treat wchar_t as built-in type" and "Enable Run-Time Type Info" to Yes. For a detailed description on how to build libtorrent with VS, see the wiki.
build configurations
By default libtorrent is built In debug mode, and will have pretty expensive invariant checks and asserts built into it. If you want to disable such checks (you want to do that in a release build) you can see the table below for which defines you can use to control the build.
| macro | description |
|---|---|
| NDEBUG | If you define this macro, all asserts, invariant checks and general debug code will be removed. Since there is quite a lot of code in in header files in libtorrent, it may be important to define the symbol consistently across compilation units, including the clients files. Potential problems is different compilation units having different views of structs and class layouts and sizes. |
| TORRENT_LOGGING | This macro will enable logging of the session events, such as tracker announces and incoming connections (as well as blocked connections). |
| TORRENT_DISABLE_GEO_IP | This is defined by default by the Jamfile. It disables the GeoIP features, and avoids linking against LGPL:ed code. |
| TORRENT_VERBOSE_LOGGING | If you define this macro, every peer connection will log its traffic to a log file as well as the session log. |
| TORRENT_STORAGE_DEBUG | This will enable extra expensive invariant checks in the storage, including logging of piece sorting. |
| TORRENT_UPNP_LOGGING | Generates a "upnp.log" file with the UPnP traffic. This is very useful when debugging support for various UPnP routers. support for various UPnP routers. |
| TORRENT_DISK_STATS | This will create a log of all disk activity which later can parsed and graphed using parse_disk_log.py. |
| TORRENT_STATS | This will generate a log with transfer rates, downloading torrents, seeding torrents, peers, connecting peers and disk buffers in use. The log can be parsed and graphed with parse_session_stats.py. |
| UNICODE | If building on windows this will make sure the UTF-8 strings in pathnames are converted into UTF-16 before they are passed to the file operations. |
| LITTLE_ENDIAN | This will use the little endian version of the sha-1 code. If defined on a big-endian system the sha-1 hashes will be incorrect and fail. If it is not defined and __BIG_ENDIAN__ isn't defined either (it is defined by Apple's GCC) both little-endian and big-endian versions will be built and the correct code will be chosen at run-time. |
| TORRENT_DISABLE_POOL_ALLOCATOR | Disables use of boost::pool<>. |
| TORRENT_LINKING_SHARED | If this is defined when including the libtorrent headers, the classes and functions will be tagged with __declspec(dllimport) on msvc and default visibility on GCC 4 and later. Set this in your project if you're linking against libtorrent as a shared library. (This is set by the Jamfile when link=shared is set). |
| TORRENT_BUILDING_SHARED | If this is defined, the functions and classes in libtorrent are marked with __declspec(dllexport) on msvc, or with default visibility on GCC 4 and later. This should be defined when building libtorrent as a shared library. (This is set by the Jamfile when link=shared is set). |
| TORRENT_DISABLE_DHT | If this is defined, the support for trackerless torrents will be disabled. |
| TORRENT_DHT_VERBOSE_LOGGING | This will enable verbose logging of the DHT protocol traffic. |
| TORRENT_DISABLE_ENCRYPTION | This will disable any encryption support and the openssl dependency that comes with it. Encryption support is the peer connection encrypted supported by clients such as uTorrent, Azureus and KTorrent. |
| _UNICODE | On windows, this will cause the file IO use wide character API, to properly support non-ansi characters. |
| TORRENT_DISABLE_RESOLVE_COUNTRIES | Defining this will disable the ability to resolve countries of origin for peer IPs. |
| TORRENT_DISABLE_INVARIANT_CHECKS | This will disable internal invariant checks in libtorrent. The invariant checks can sometime be quite expensive, they typically don't scale very well. This option can be used to still build in debug mode, with asserts enabled, but make the resulting executable faster. |
| TORRENT_EXPENSIVE_INVARIANT_CHECKS | This will enable extra expensive invariant checks. Useful for finding particular bugs or for running before releases. |
| TORRENT_NO_DEPRECATE | This will exclude all deprecated functions from the header files and cpp files. |
If you experience that libtorrent uses unreasonable amounts of cpu, it will definitely help to define NDEBUG, since it will remove the invariant checks within the library.
building openssl for windows
To build openssl for windows with Visual Studio 7.1 (2003) execute the following commands in a command shell:
perl Configure VC-WIN32 --prefix="c:/openssl call ms\do_nasm call "C:\Program Files\Microsoft Visual Studio .NET 2003\vc7\bin\vcvars32.bat" nmake -f ms\nt.mak copy inc32\openssl "C:\Program Files\Microsoft Visual Studio .NET 2003\vc7\include\" copy out32\libeay32.lib "C:\Program Files\Microsoft Visual Studio .NET 2003\vc7\lib" copy out32\ssleay32.lib "C:\Program Files\Microsoft Visual Studio .NET 2003\vc7\lib"
This will also install the headers and library files in the visual studio directories to be picked up by libtorrent.