I assume due to the fact Big Sur is sparkling new hotfixes for the new OS have not yet happen. When attempting to install modules that use clang for compilation, the following error is thrown:

clang: error: invalid version number in 'MACOSX_DEPLOYMENT_TARGET=11.0'

Currently running:

  • Mac OS Big Sur, 11.0 Beta
  • Intel CPU (i386)
  • Python 3.8.0 installed via pyenv

Multiple modules have clang dependencies, and so it seems this error is quite common. An example:

pip install multidict

Installing older versions of Command Line Tools (e.g. 11.5) does not work as well.

I would like to extend @Felipe excellent answer; if it doesn’t work even with running

>>> softwareupdate --all --install --force
Software Update Tool

Finding available software
No updates are available.

…following the wisdom of the “homebrew doctor” solves it, i.e. remove and reinstall:

sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install

Figure out the issue on my end.

Previously I had installed XCode from the App Store (11.7) and set its SDKs as my default:

sudo xcode-select --switch /Applications/Xcode.app/

However, it seems this come with an unsupported version of clang:

  ? clang --version
Apple clang version 11.0.3 (clang-1103.0.32.62)
Target: x86_64-apple-darwin20.1.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Setting the xcode-select to the latest version via:

sudo xcode-select --switch /Library/Developer/CommandLineTools

EDIT (11/15/2020)

You might receive an error when attempting the above change:

xcode-select: error: invalid developer directory '/Library/Developer/CommandLineTools'

To fix this, you must install the latest Command Line Tools from the official Apple website here. At the time of writting this edit, I installed the Command Line Tools for Xcode 12.3 beta.

Changes clang to a working version:

  ? clang --version
Apple clang version 12.0.0 (clang-1200.0.32.2)
Target: x86_64-apple-darwin20.1.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

The built-in Big Sur SDK is version 10.15, which seems to work without an issue:

  ? ls /Library/Developer/CommandLineTools/SDKs
MacOSX.sdk      MacOSX10.15.sdk

After the switch, multidict was installed successfully.

  ? pip install multidict
Collecting multidict
  Downloading multidict-4.7.6-cp38-cp38-macosx_10_14_x86_64.whl (48 kB)
     |????????????????????????????????| 48 kB 589 kB/s
Installing collected packages: multidict
Successfully installed multidict-4.7.6

Further investigation seems to indicate this is a design choice by Apple (source):

enter image description here

Therefore, ensuring your SDK is the default out-of-the-box as opposed to XCode’s new SDK should be enough for the system to switch context when needed (and seems to work fine with pip+clang).

I had already removed and reinstalled xtools CLI, but the error persisted..

All I needed to do was

export SYSTEM_VERSION_COMPAT=1

then the error went away

in my case I had to remove /Library/Developer/CommandLineTools and re-install command line tools

% sudo rm -rf /Library/Developer/CommandLineTools
% sudo xcode-select --install
% clang --version
Apple clang version 12.0.0 (clang-1200.0.32.27)
Target: x86_64-apple-darwin20.1.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

In my case removing CLT and LLVM and setting XCode just compiled.

% sudo rm -rf /Library/Developer/CommandLineTools
% sudo xcode-select --switch /Applications/Xcode.app
% brew uninstall llvm # if installed via brew
% clang --version
Apple clang version 12.0.0 (clang-1200.0.32.28)
Target: x86_64-apple-darwin20.2.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

gcc and g++ now compiling without any error.

For my case, to be safe, I renamed the existing directory and reinstalled the latest one. The “clang” build error is gone right after the update.

Before:

$ clang --version
Apple clang version 11.0.3 (clang-1103.0.32.62)
Target: x86_64-apple-darwin21.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools

Action:

sudo mv /Library/Developer/CommandLineTools /Library/Developer/CommandLineTools.old
sudo xcode-select --install

After:

$ clang --version
Apple clang version 13.0.0 (clang-1300.0.27.3)
Target: x86_64-apple-darwin21.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

macOS Monterey 12.3.2 failed to install a new version of python.

$ pyenv install 3.8.4

found it was due to a bug in the latest version of Monterey as MACOSX_DEPLOYMENT_TARGET was previously set to 12.3.

Fixed it by setting MACOSX_DEPLOYMENT_TARGET=12.3.0

% pyenv install 3.8.4
python-build: use [email protected] from homebrew
python-build: use readline from homebrew
Downloading Python-3.8.4.tar.xz...
-> https://www.python.org/ftp/python/3.8.4/Python-3.8.4.tar.xz
Installing Python-3.8.4...
patching file Misc/NEWS.d/next/Build/2021-10-11-16-27-38.bpo-45405.iSfdW5.rst
patching file configure
patching file configure.ac
python-build: use tcl-tk from homebrew
python-build: use readline from homebrew
python-build: use zlib from xcode sdk

BUILD FAILED (OS X 12.3.1 using python-build 20180424)

Inspect or clean up the working tree at /var/folders/5r/61nxx8hs53x6hhzm_r86jhjrq0r6qq/T/python-build.20220504193655.2344
Results logged to /var/folders/5r/61nxx8hs53x6hhzm_r86jhjrq0r6qq/T/python-build.20220504193655.2344.log

Last 10 log lines:
checking for python3... python3
checking for --enable-universalsdk... no
checking for --with-universal-archs... no
checking MACHDEP... "darwin"
checking for gcc... clang
checking whether the C compiler works... no
configure: error: in `/var/folders/5r/61nxx8hs53x6hhzm_r86jhjrq0r6qq/T/python-build.20220504193655.2344/Python-3.8.4':
configure: error: C compiler cannot create executables
See `config.log' for more details
make: *** No targets specified and no makefile found.  Stop.

After fix:

 % pyenv install 3.8.4
python-build: use [email protected] from homebrew
python-build: use readline from homebrew
Downloading Python-3.8.4.tar.xz...
-> https://www.python.org/ftp/python/3.8.4/Python-3.8.4.tar.xz
Installing Python-3.8.4...
patching file Misc/NEWS.d/next/Build/2021-10-11-16-27-38.bpo-45405.iSfdW5.rst
patching file configure
patching file configure.ac
python-build: use tcl-tk from homebrew
python-build: use readline from homebrew
python-build: use zlib from xcode sdk
Installed Python-3.8.4 to /Users/{USER}/.pyenv/versions/3.8.4