LLDB relies on many of the technologies developed by the larger LLVM project.
In particular, it requires both Clang and LLVM itself in order to build. Due to
this tight integration the Getting Started guides for both of these projects
come as prerequisite reading:
Supported compilers for building LLDB on Linux include:
- Clang 3.2
- GCC 4.6.2 (later versions should work as well)
It is recommended to use libstdc++ 4.6 (or higher) to build LLDB on Linux, but using libc++ is also known to work.
On FreeBSD the base system Clang and libc++ may be used to build LLDB,
or the GCC port or package.
In addition to any dependencies required by LLVM and Clang, LLDB needs a few
development packages that may also need to be installed depending on your
system. The current list of dependencies are:
So for example, on a Fedora system one might run:
> yum install swig python-devel libedit-devel
On a Debian or Ubuntu system one might run:
> sudo apt-get install build-essential subversion swig python2.7-dev libedit-dev libncurses5-dev
> sudo apt-get build-dep lldb-3.3 # or lldb-3.4
On FreeBSD one might run:
> pkg install swig python
If you wish to build the optional reference documentation, additional dependencies are required:
- Graphviz (for the 'dot' tool).
- doxygen (only if you wish to build the C++ API reference)
- epydoc (only if you wish to build the Python API reference)
To install the prerequisites for building the documentation (on Debian/Ubuntu) do:
> sudo apt-get install doxygen graphviz
> sudo pip install epydoc # or install package python-epydoc
We first need to checkout the source trees into the appropriate locations. Both
Clang and LLDB build as subprojects of LLVM. This means we will be checking out
the source for both Clang and LLDB into the tools subdirectory of LLVM. We
will be setting up a directory hierarchy looking something like this:
For reference, we will call the root of the LLVM project tree $llvm, and the
roots of the Clang and LLDB source trees $clang and $lldb respectively.
Change to the directory where you want to do development work and checkout LLVM:
> svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
Now switch to LLVM’s tools subdirectory and checkout both Clang and LLDB:
> cd $llvm/tools
> svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
> svn co http://llvm.org/svn/llvm-project/lldb/trunk lldb
In general, building the LLDB trunk revision requires trunk revisions of both
LLVM and Clang.
It is highly recommended that you build the system out of tree. Create a second
build directory and configure the LLVM project tree to your specifications as
outlined in LLVM’s Getting Started Guide. A typical build procedure
> cd $llvm/..
> mkdir build
> cd build
To build with CMake
Using CMake is documented on the Building LLVM with CMake
page. Building LLDB is possible using one of the following generators:
Using CMake + Ninja
Ninja is the fastest way to build LLDB! In order to use ninja, you need to have recent versions of CMake and
ninja on your system. To build using ninja:
> cmake .. -G Ninja
> ninja lldb
> ninja check-lldb
Using CMake + Unix Makefiles
If you do not have Ninja, you can still use CMake to generate Unix Makefiles that build LLDB:
> cmake ..
> make check-lldb
To build with autoconf
If you do not have CMake, it is still possible to build LLDB using the autoconf build system. If you are using
Clang or GCC 4.8+, run:
If you are building with a GCC that isn't the default gcc/g++, like gcc-4.9/g++-4.9
> $llvm/configure CC=gcc-4.9 CXX=g++-4.9
> make CC=gcc-4.9 CXX=g++-4.9
If you are running in a system that doesn't have a lot of RAM (less than 4GB), you might want to disable
debug symbols by specifying DEBUG_SYMBOLS=0 when running make. You will know if you need to enable this
because you will fail to link clang (the linker will get a SIGKILL and exit with status 9).
> make DEBUG_SYMBOLS=0
To run the LLDB test suite, run:
> make -C tools/lldb/test
Note that once both LLVM and Clang have been configured and built it is not
necessary to perform a top-level make to rebuild changes made only to LLDB.
You can run make from the build/tools/lldb subdirectory as well.
If you wish to build with libc++ instead of libstdc++ (the default), run configure with the
If you wish to build a release version of LLDB, run configure with the --enable-optimized flag.
Building API reference documentation
LLDB exposes a C++ as well as a Python API. To build the reference documentation for these two APIs, ensure you have
the required dependencies installed, and build the lldb-python-doc and lldb-cpp-doc CMake targets.
The output HTML reference documentation can be found in <build-dir>/tools/lldb/docs/.
LLDB has a Python scripting capability and supplies its own Python module named lldb.
If a script is run inside the command line lldb application, the Python module
is made available automatically. However, if a script is to be run by a Python interpreter
outside the command line application, the PYTHONPATH environment variable can be used
to let the Python interpreter find the lldb module.
The correct path can be obtained by invoking the command line lldb tool with the -P flag:
> export PYTHONPATH=`$llvm/build/Debug+Asserts/bin/lldb -P`
If you used a different build directory or made a release build, you may need to adjust the
above to suit your needs. To test that the lldb Python module
is built correctly and is available to the default Python interpreter, run:
> python -c 'import lldb'
In order to debug remote targets running different architectures than your host, you
will need to compile LLDB (or at least the server component) for the target. While
the easiest solution is to just compile it locally on the target, this is often not
feasable, and in these cases you will need to cross-compile LLDB on your host.
Cross-compilation is often a daunting task and has a lot of quirks which depend on
the exact host and target architectures, so it is not possible to give a universal
guide which will work on all platforms. However, here we try to provide an overview
of the cross-compilation process along with the main things you should look out for.
First, you will need a working toolchain which is capable of producing binaries for
the target architecture. Since you already have a checkout of clang and lldb, you
can compile a host version of clang in a separate folder and use that.
Alternatively you can use system clang or even cross-gcc if your distribution
provides such packages (e.g.,
g++-aarch64-linux-gnu on Ubuntu). On
Android, a working toolchain can be produced by downloading the Android NDK and
running the contained
Next, you will need a copy of the required target headers and libraries on your
host. The libraries can be usually obtained by copying from the target machine,
however the headers are often not found there, especially in case of embedded
platforms. In this case, you will need to obtain them from another source, either
a cross-package if one is available, or cross-compiling the respective library from
source. Fortunately the list of LLDB dependencies is not big and if you are only
interested in the server component, you can reduce this even further by passing the
appropriate cmake options, such as:
In this case you, will often not need anything other than the standard C and C++
In the case of Android, all required headers and libraries are provided by the
Once all of the dependencies are in place, it's just a matter of configuring the
build system with the locations and arguments of all the necessary tools. The most
important cmake options here are:
- Set to 1 to enable cross-compilation.
- Affects the cmake search path when looking for libraries. You may need to set
this to your architecture triple if you do not specify all your include and
library paths explicitly.
- CMAKE_C_COMPILER, CMAKE_CXX_COMPILER
- C and C++ compilers for the target architecture
- CMAKE_C_FLAGS, CMAKE_CXX_FLAGS
- The flags for the C and C++ target compilers. You may need to specify the
exact target cpu and abi besides the include paths for the target headers.
- The flags to be passed to the linker. Usually just a list of library search
paths referencing the target libraries.
- LLVM_TABLEGEN, CLANG_TABLEGEN
- Paths to llvm-tblgen and clang-tblgen for the host architecture. If
you already have built clang for the host, you can point these variables to the
executables in your build directory. If not, you will need to build the
llvm-tblgen and clang-tblgen host targets at least.
- The triple of the system that lldb (or lldb-server) will run on. Not setting
this (or setting it incorrectly) can cause a lot of issues with remote debugging
as a lot of the choices lldb makes depend on the triple reported by the remote
You can of course also specify the usual cmake options like CMAKE_BUILD_TYPE, etc.
Example 1: Cross-compiling for linux arm64 on Ubuntu host
Ubuntu already provides the packages necessary to cross-compile LLDB for arm64. It
is sufficient to install pacakges gcc-aarch64-linux-gnu, g++-aarch64-linux-gnu,
binutils-aarch64-linux-gnu. Then it is possible to prepare the cmake build with the
An alternative (and recommended) way to compile LLDB is with clang. Unfortunately,
clang is not able to find all the include paths necessary for a successful
cross-compile, so we need to help it with a couple of CFLAGS options. In my case it
was sufficient to add the following arguments to CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
(in addition to changing CMAKE_C(XX)_COMPILER to point to clang compilers):
-target aarch64-linux-gnu \
-I /usr/aarch64-linux-gnu/include/c++/4.8.2/aarch64-linux-gnu \
If you wanted to build a full version of LLDB and avoid passing
-DLLDB_DISABLE_PYTHON and other options, you would need to obtain the target
versions of the respective libraries. The easiest way to achive this is to use the
qemu-debootstrap utility, which can prepare a system image using qemu
and chroot to simulate the target environment. Then you can install the necessary
packages in this environment (python-dev, libedit-dev, etc.) and point your
compiler to use them using the correct -I and -L arguments.
Example 2: Cross-compiling for Android on Linux
All tools needed to build LLDB for android are available in the Android NDK. For
example, we can produce an x86 toolchain along with all the libraries and headers
from inside the unzipped NDK. Toolchains for other architectures can be produced in
a similar manner.
For Android we provide a Android.cmake script which sets a lot of the required
options automatically. A cmake build can therefore be prepared with the following parameters:
Note that the full LLVM build is not functional on android yet, so simply runing
ninja will not work. You will need to manually specify the target you
want to build: