[lldb-dev] [llvm-dev] 12.0.0-rc1 Release has been tagged

[Dimitry Andric via lldb-dev]

On 28 Jan 2021, at 05:05, Tom Stellard via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I've tagged the 12.0.0-rc1 release.  Testers can begin testing and upload binaries.

During 12.0.0-rc1 test builds on FreeBSD, I encountered this unittest failure, which turned out to be caused by recent libc++ changes:

  FAILED: tools/clang/bindings/python/tests/CMakeFiles/check-clang-python
  cd /home/dim/llvm/12.0.0/llvm-project/clang/bindings/python && /usr/local/bin/cmake -E env CLANG_LIBRARY_PATH=/home/dim/obj/llvmorg-12.0.0-rc1-2-gdf959fc2eb7e-1/lib /usr/local/bin/python3.7 -m unittest discover
  EEEEEEEE

The 'EEEEEEEE' signifies 8 errors, which become more clear if "unittest discover" is run with the -f (fail immediately) and -v (verbose) options:

  $ cd /home/dim/llvm/12.0.0/llvm-project/clang/bindings/python && /usr/local/bin/cmake -E env CLANG_LIBRARY_PATH=/home/dim/obj/llvmorg-12.0.0-rc1-2-gdf959fc2eb7e-1/lib /usr/local/bin/python3.7 -m unittest discover -f -v
  test_access_specifiers (tests.cindex.test_access_specifiers.TestAccessSpecifiers)
  Ensure that C++ access specifiers are available on cursors ... ERROR

  ======================================================================
  ERROR: test_access_specifiers (tests.cindex.test_access_specifiers.TestAccessSpecifiers)
  Ensure that C++ access specifiers are available on cursors
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 4173, in get_cindex_library
      library = cdll.LoadLibrary(self.get_filename())
    File "/usr/local/lib/python3.7/ctypes/__init__.py", line 442, in LoadLibrary
      return self._dlltype(name)
    File "/usr/local/lib/python3.7/ctypes/__init__.py", line 364, in __init__
      self._handle = _dlopen(self._name, mode)
  OSError: /home/dim/obj/llvmorg-12.0.0-rc1-2-gdf959fc2eb7e-1/lib/../lib/libc++.so.1: Undefined symbol "_ZnamSt11align_val_t"

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/tests/cindex/test_access_specifiers.py", line 29, in test_access_specifiers
      """, lang = 'cpp')
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/tests/cindex/util.py", line 41, in get_tu
      source)])
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 2812, in from_source
      index = Index.create()
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 2699, in create
      return Index(conf.lib.clang_createIndex(excludeDecls, 0))
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 212, in __get__
      value = self.wrapped(instance)
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 4147, in lib
      lib = self.get_cindex_library()
    File "/home/dim/llvm/12.0.0/llvm-project/clang/bindings/python/clang/cindex.py", line 4178, in get_cindex_library
      raise LibclangError(msg)
  clang.cindex.LibclangError: /home/dim/obj/llvmorg-12.0.0-rc1-2-gdf959fc2eb7e-1/lib/../lib/libc++.so.1: Undefined symbol "_ZnamSt11align_val_t". To provide a path to libclang use Config.set_library_path() or Config.set_library_file().

  ----------------------------------------------------------------------
  Ran 1 test in 0.027s

  FAILED (errors=1)

It turns out that libc++.so.1 now depends on the symbol '_ZnamSt11align_val_t', which is 'operator new [](unsigned long, std::align_val_t)'. Embarassingly, libc++.so.1 has always depended on this C++17 specific variant of operator new. But FreeBSD's C++ ABI library, libcxxrt, has never supported this variant!

Previously, this never was a problem, because libc++ provided its own weak definitions of these operators. But recently the define _LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS was toggled to on by default, which disables those definitions. This happened in 9b40ee8eb0c194f4b2787801ac6f9ef8fc1b8f46 ("[libc++] Define new/delete in libc++abi only by default") by Louis Dionne.

While this is reasonable for the libc++abi situation, where it might lead to circular dependencies, I would like to turn the definitions on again in case libcxxrt is used for the C++ ABI, such as on FreeBSD.

If you think this is a reasonable approach, I will create a review for it. Otherwise, I will have to patch the test-release.sh script to pass -DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS=ON to the CMake command line on FreeBSD.

-Dimitry

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