Where to find the LLDB Pipeline

[MrSarius]

Where can I find the pipeline (lldb-build) that builds the self-contained version of LLDB? I'd be interested in seeing how the self-contained version of LLDB is built.

[vadimcn]

It isn't publicly available.

[MrSarius]

Hello.
Thank you for the quick reply. Maybe you can help me anyway.

I want to compile a LLDB binary with Python scripting support for different platforms (macOS and Ubuntu, both x86) in my pipeline and make it available for download as a zip file. When I add -DLLDB_ENABLE_PYTHON:BOOL=ON to the cmake configuration, the binary only looks for that specific Python version that cmake found. Can the bianry also dynamically look for any working python3 version or do I then have to include python in my zip?

A self contained version (like you did with codeLLDB) would also be fine, is there a cmake flag that makes LLDB copy everything it needs into the lib folder?

Thank you :)

[vadimcn]

Can the bianry also dynamically look for any working python3 version or do I then have to include python in my zip?

Generally speaking, Python ABI is not cross-compatible between minor versions. Although stable Python ABI does exist, LLDB does not stick to this subset. LLDB's build scripts will copy Python libs into the output directory if you set LLDB_PYTHON_RELATIVE_PATH. These are Python-related flags I set during builds:

LLDB_ENABLE_PYTHON=TRUE
LLDB_EMBED_PYTHON_HOME=TRUE
LLDB_PYTHON_HOME=..
LLDB_PYTHON_RELATIVE_PATH=lib/lldb-python
LLDB_PYTHON_EXE_RELATIVE_PATH=python3
LLDB_PYTHON_EXT_SUFFIX=.so

I don't remember exactly how I came up with this set, so please don't ask.

... The other thing you'll have to worry about is compatibility with Linux system libraries, which various Python built-in modules depend on, starting with glibc. For this reason, I use the Python distribution from this project.

[MrSarius]

Thank you that was very helpful already.

A few more questions:

• Can I define synthetic children in LLDB without python support? I guess no?
• Why not building python from scratch for each platform and distribute this with lldb? Usually a modern OS comes with pythons dependencies like libc pre-installed, right?
  • Or could you elaborate a bit more why we need a stand alone version of python?

[vadimcn]

Can I define synthetic children in LLDB without python support? I guess no?

Not that I know of.

...why we need a stand alone version of python?

• I must choose the specific version of Python that LLDB is built against.
• I cannot expect to find this particular version on a random machine that CodeLLDB gets dropped on, so I must bundle it.
• I cannot just bundle Python that comes with my Linux distro, because it expects to be installed via the package manager, so it depends on lots of shared libs, including a pretty recent glibc.

Standalone Python uses static linking to the maximum possible extent, so it depends only on shared libs available in most bare-bones Linux installations.

[MrSarius]

Thanks for all your help but I still have a question...

How do you tell cmake not to take the Python from the system, but the stand alone build? For me, find_package() always resolves the system python.

With -DPython3_ROOT_DIR I get CMake to use the standalone build, but the executable still fails with this error message.

./lldb
dyld[36134]: Library not loaded: /install/lib/libpython3.10.dylib
...

I don't understand where /install/... comes from?

[vadimcn]

Not sure... Try examining the output of otool -L ./lldb. Maybe you need to set RPATH?

[vadimcn]

If cmake is not finding the right Python, tweaking other search hints. If nothing else works, you can try setting Python3_EXECUTABLE and Python3_LIBRARIES explicitly.

[MrSarius]

I think -DPython3_ROOT_DIR sets Python3_EXECUTABLE and Python3_LIBRARIES explicitly. As I said, CMake finds the correct Python with -DPython3_ROOT_DIR.

I have no clue where this path comes from 😓:

$ otool -L ../lib/liblldb.dylib
	@rpath/liblldb.13.0.1.dylib (compatibility version 0.0.0, current version 13.0.1)
	...
	/install/lib/libpython3.10.dylib (compatibility version 3.10.0, current version 3.10.0)

Where do you put the Python stand alone folder while you compile LLDB? So that CMake finds it without explicitly setting the paths?

[MrSarius]

This is the output for your liblldb.

$ otool -L liblldb.dylib 
liblldb.dylib:
	@rpath/liblldb.dylib (compatibility version 0.0.0, current version 0.0.0)
	...
	@rpath/libpython39.dylib (compatibility version 0.0.0, current version 0.0.0)