[lldb] Support a Stable ABI LLDB_PYTHON_EXT_SUFFIX

[JDevlieghere]

When building against the Python Stable API, we should use the abi3 ABI tag. Otherwise, Python will refuse to import the native shared object. This PR adds support for generating a stable ABI compatible suffix when LLDB_ENABLE_PYTHON_LIMITED_API is set.

Previously, on Darwin when building against Python 3.14, you would end up with _lldb.cpython-314-darwin.so. Now, when using the stable ABI, you get _lldb.abi3.so instead. A different version of the Python interpreter will not consider loading the former, but will load the latter.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

Changes

When building against the Python Stable API, we should use the abi3 ABI tag. Otherwise, Python will refuse to import the native shared object. This PR adds support for generating a stable ABI compatible suffix when LLDB_ENABLE_PYTHON_LIMITED_API is set.

---

Full diff: https://github.com/llvm/llvm-project/pull/166269.diff

2 Files Affected:

• (modified) lldb/CMakeLists.txt (+5)
• (modified) lldb/bindings/python/get-python-config.py (+7-1)

diff --git a/lldb/CMakeLists.txt b/lldb/CMakeLists.txt
index 01b5546fee00d..0736e6ba132c8 100644
--- a/lldb/CMakeLists.txt
+++ b/lldb/CMakeLists.txt
@@ -62,11 +62,16 @@ if (LLDB_ENABLE_PYTHON)
   set(cachestring_LLDB_PYTHON_EXT_SUFFIX
     "Filename extension for native code python modules")
 
+  if (LLDB_ENABLE_PYTHON_LIMITED_API)
+    set(stable_abi "--stable-abi")
+  endif()
+
   foreach(var LLDB_PYTHON_RELATIVE_PATH LLDB_PYTHON_EXE_RELATIVE_PATH LLDB_PYTHON_EXT_SUFFIX)
     if(NOT DEFINED ${var} AND NOT CMAKE_CROSSCOMPILING)
       execute_process(
         COMMAND ${Python3_EXECUTABLE}
           ${CMAKE_CURRENT_SOURCE_DIR}/bindings/python/get-python-config.py
+          ${stable_abi}
           ${var}
         OUTPUT_VARIABLE value
         OUTPUT_STRIP_TRAILING_WHITESPACE)
diff --git a/lldb/bindings/python/get-python-config.py b/lldb/bindings/python/get-python-config.py
index ae84cbb1215a9..bf8cc48b013e1 100755
--- a/lldb/bindings/python/get-python-config.py
+++ b/lldb/bindings/python/get-python-config.py
@@ -18,6 +18,9 @@ def relpath_nodots(path, base):
 def main():
     parser = argparse.ArgumentParser(description="extract cmake variables from python")
     parser.add_argument("variable_name")
+    parser.add_argument(
+        "--stable-abi", action="store_true", help="Target the Stable C ABI"
+    )
     args = parser.parse_args()
     if args.variable_name == "LLDB_PYTHON_RELATIVE_PATH":
         # LLDB_PYTHON_RELATIVE_PATH is the relative path from lldb's prefix
@@ -68,7 +71,10 @@ def main():
                     print("sys.prefix:", sys.prefix, file=sys.stderr)
                     sys.exit(1)
     elif args.variable_name == "LLDB_PYTHON_EXT_SUFFIX":
-        print(sysconfig.get_config_var("EXT_SUFFIX"))
+        if args.stable_abi:
+            print(".abi3%s" % sysconfig.get_config_var("SHLIB_SUFFIX"))
+        else:
+            print(sysconfig.get_config_var("EXT_SUFFIX"))
     else:
         parser.error(f"unknown variable {args.variable_name}")
 

[JDevlieghere]

I couldn't find a way to get this programmatically, though it's mentioned for example in https://peps.python.org/pep-0720/.

[DavidSpickett]

I do see code using EXTENSION_SUFFIXES and checking for the entry that contains .abi3. It doesn't say it has a set order and in theory I could make my strange platform's shared object suffix start with .abi3 and end up with .cpython-311-x86_64-linux-letsbreakassumptions.abi3askingfortrouble as one of the entries.

So yes, what you've done is fine.

[medismailben]

LGTM!

[DavidSpickett]

LGTM

I tried to find a citation for the . being included and the best I could find was this bug report comment - https://bugs.python.org/msg185870.

Clearly it works for you though so it must include the ..