The LLDB Debugger#
Welcome to the LLDB documentation!
LLDB is a next generation, high-performance debugger. It is built as a set of reusable components which highly leverage existing libraries in the larger LLVM Project, such as the Clang expression parser and LLVM disassembler.
LLDB is the default debugger in Xcode on macOS and supports debugging C, Objective-C and C++ on the desktop and iOS devices and simulator.
All of the code in the LLDB project is available under the “Apache 2.0 License with LLVM exceptions”.
For an introduction into the LLDB command language, head over to the LLDB Tutorial. For users already familiar with GDB there is a cheat sheet listing common tasks and their LLDB equivalent in the GDB to LLDB command map.
There are also multiple resources on how to script LLDB using Python: the Python Reference is a great starting point for that.
Compiler Integration Benefits#
LLDB converts debug information into Clang types so that it can leverage the Clang compiler infrastructure. This allows LLDB to support the latest C, C++, Objective-C and Objective-C++ language features and runtimes in expressions without having to reimplement any of this functionality. It also leverages the compiler to take care of all ABI details when making functions calls for expressions, when disassembling instructions and extracting instruction details, and much more.
The major benefits include:
Up to date language support for C, C++, Objective-C
Multi-line expressions that can declare local variables and types
Utilize the JIT for expressions when supported
Evaluate expression Intermediate Representation (IR) when JIT can’t be used
The LLDB debugger APIs are exposed as a C++ object oriented interface in a shared library. The lldb command line tool links to, and uses this public API. On macOS the shared library is exposed as a framework named LLDB.framework, and Unix systems expose it as lldb.so. The entire API is also then exposed through Python script bindings which allow the API to be used within the LLDB embedded script interpreter, and also in any python script that loads the lldb.py module in standard python script files. See the Python Reference page for more details on how and where Python can be used with the LLDB API.
Sharing the LLDB API allows LLDB to not only be used for debugging, but also for symbolication, disassembly, object and symbol file introspection, and much more.
LLDB is known to work on the following platforms, but ports to new platforms are welcome:
macOS debugging for i386, x86_64 and AArch64
iOS, tvOS, and watchOS simulator debugging on i386, x86_64 and AArch64
iOS, tvOS, and watchOS device debugging on ARM and AArch64
Linux user-space debugging for i386, x86_64, ARM, AArch64, PPC64le, s390x
FreeBSD user-space debugging for i386, x86_64, ARM, AArch64, MIPS64, PPC
NetBSD user-space debugging for i386 and x86_64
Windows user-space debugging for i386, x86_64, ARM and AArch64 (*)
(*) Support for Windows is under active development. Basic functionality is expected to work, with functionality improving rapidly. ARM and AArch64 support is more experimental, with more known issues than the others.
Check out the LLVM source-tree with git and find the sources in the
$ git clone https://github.com/llvm/llvm-project.git
Note that LLDB generally builds from top-of-trunk using CMake and Ninja. Additionally it builds:
on macOS with a generated Xcode project
on Linux and FreeBSD with Clang and libstdc++/libc++
on NetBSD with GCC/Clang and libstdc++/libc++
on Windows with a generated project for VS 2017 or higher
See the LLDB Build Page for build instructions.
See the Projects page if you are looking for some interesting areas to contribute to lldb.