PyROOT macro compilation fails on macOS due to libffi-trampolines.dylib linking restriction

[diegobaronm]

brew config AND brew doctor output OR brew gist-logs <formula> link

brew doctor:

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  icu4c@77

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae and may need to be deleted.

Unexpected dylibs:
  /usr/local/lib/libcvmfs_cache.2.12.0.dylib
  /usr/local/lib/libcvmfs_client.2.12.0.dylib
  /usr/local/lib/libcvmfs_crypto.2.12.0.dylib
  /usr/local/lib/libcvmfs_crypto_debug.2.12.0.dylib
  /usr/local/lib/libcvmfs_fuse.2.12.0.dylib
  /usr/local/lib/libcvmfs_fuse_debug.2.12.0.dylib
  /usr/local/lib/libcvmfs_fuse_stub.2.12.0.dylib
  /usr/local/lib/libcvmfs_util.2.12.0.dylib
  /usr/local/lib/libcvmfs_util_debug.2.12.0.dylib

Warning: Unbrewed header files were found in /usr/local/include.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae and may need to be deleted.

Unexpected header files:
  /usr/local/include/libcvmfs.h
  /usr/local/include/libcvmfs_cache.h

brew config:

HOMEBREW_VERSION: 5.1.0
ORIGIN: https://github.com/Homebrew/brew
HEAD: 4135badeddc3899aa2e89d3ea1caee320c55d299
Last commit: 3 days ago
Branch: stable
Core tap JSON: 14 Mar 19:42 UTC
Core cask tap JSON: 14 Mar 19:42 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.QgQccCRKRl/org.xquartz:0
HOMEBREW_DOWNLOAD_CONCURRENCY: 20
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 10
Homebrew Ruby: 4.0.1 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/4.0.1/bin/ruby
CPU: deca-core 64-bit arm_blizzard_avalanche
Clang: 17.0.0 build 1700
Git: 2.50.1 => /Applications/Xcode.app/Contents/Developer/usr/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 26.3.1-arm64
CLT: 26.3.0.0.1.1771626560
Xcode: 26.3
Metal Toolchain: N/A
Rosetta 2: false

Verification

• My brew doctor output says Your system is ready to brew. and am still able to reproduce my issue.
• I ran brew update and am still able to reproduce my issue.
• I have resolved all warnings from brew doctor and that did not fix my problem.
• I searched for recent similar issues at https://github.com/Homebrew/homebrew-core/issues?q=is%3Aissue and found no duplicates.
• My issue is not about a failure to build a formula from source.

What were you trying to do (and why)?

I am trying to use PyROOT from the ROOT homebrew installation.
This has been also flagged to the ROOT developers here

Thanks in advance!

What happened (include all command output)?

I get the following linker error:

Info in <TMacOSXSystem::ACLiC>: creating shared library /Users/user/Downloads/./test_cpp.so
ld: cannot link directly with 'libffi-trampolines.dylib' because product being built is not an allowed client of it
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
Error in <ACLiC>: Executing 'cd "/Users/user/Downloads" ; clang++ -fPIC -c -O3 -DNDEBUG -Wc++11-narrowing -Wsign-compare -Wsometimes-uninitialized -Wconditional-uninitialized -Wheader-guard -Warray-bounds -Wcomment -Wtautological-compare -Wstrncat-size -Wloop-analysis -Wbool-conversion -m64 -pipe -W -Woverloaded-virtual -fsigned-char -fsized-deallocation -fno-common -Qunused-arguments -pthread -stdlib=libc++ -std=c++17  -I/opt/homebrew/Cellar/root/6.38.04/include/root -isysroot "/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk" -I"/opt/homebrew/Cellar/root/6.38.04/etc/root" -I"/opt/homebrew/Cellar/root/6.38.04/etc/root/cling" -I"/opt/homebrew/Cellar/root/6.38.04/etc/root/cling/plugins/include" -I"/opt/homebrew/Cellar/root/6.38.04/include/root" -I"/opt/homebrew/include" -I"/opt/homebrew/opt/python@3.14/Frameworks/Python.framework/Versions/3.14/include/python3.14"   -D__ACLIC__ "/Users/user/Downloads/test_cpp_ACLiC_dict.cxx" ; clang++ -O3 -DNDEBUG "/Users/user/Downloads/test_cpp_ACLiC_dict.o" -dynamiclib -Wl,-w -Wl,-undefined,dynamic_lookup -Wl,-headerpad_max_install_names -m64 -Wl,-dead_strip_dylibs -Wl,-rpath,/opt/homebrew/Cellar/root/6.38.04/lib/root   "/opt/homebrew/Cellar/python@3.14/3.14.3_1/Frameworks/Python.framework/Versions/3.14/Python" "/usr/lib/libffi-trampolines.dylib" "/opt/homebrew/Cellar/root/6.38.04/lib/root/cppyy/libcppyy.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libCPyCppyy.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libCore.so" "/opt/homebrew/Cellar/pcre2/10.47_1/lib/libpcre2-8.0.dylib" "/opt/homebrew/Cellar/xz/5.8.2/lib/liblzma.5.dylib" "/opt/homebrew/Cellar/xxhash/0.8.3/lib/libxxhash.0.8.3.dylib" "/opt/homebrew/Cellar/lz4/1.10.0/lib/liblz4.1.10.0.dylib" "/opt/homebrew/Cellar/zstd/1.5.7_1/lib/libzstd.1.5.7.dylib" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libRIO.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libThread.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libCling.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/ROOT/libROOTPythonizations.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libTree.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libImt.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libNet.so" "/opt/homebrew/Cellar/root/6.38.04/lib/root/libMultiProc.so" "/opt/homebrew/Cellar/tbb/2022.3.0/lib/libtbb.12.17.dylib" "/opt/homebrew/Cellar/openssl@3/3.6.1/lib/libssl.3.dylib" "/opt/homebrew/Cellar/openssl@3/3.6.1/lib/libcrypto.3.dylib" "/opt/homebrew/Cellar/tbb/2022.3.0/lib/libtbbmalloc.2.17.dylib" -o "/Users/user/Downloads/./test_cpp.so"' failed!

What did you expect to happen?

Just normal compilation. I noticed that if I do:

export DYLD_LIBRARY_PATH=/opt/homebrew/opt/libffi/lib:$DYLD_LIBRARY_PATH

the problem goes away.

Step-by-step reproduction instructions (by running brew commands)

# Install ROOT with brew

brew install root

# Create a test macro to compile using PyROOT
Name the file `test.cpp`

#include <iostream>
void test() {
    std::cout << "hello" << std::endl;
}

# Use Python / PyROOT to compile

python3
import ROOT
ROOT.gROOT.ProcessLine(".L test_macro.C+")

[cho-m]

Sounds like an upstream issue but would need further analysis by someone familiar with ROOT internals to be sure.

Specifically, it is suspicious that ROOT is trying to link to /usr/lib/libffi-trampolines.dylib. The dylib is part of Apple's libffi and should not be directly used. Instead, standard -lffi (going through Apple's libffi.tbd/libffi.dylib setup) is used and then libffi-trampolines.dylib is dlopen-ed internally:

• https://github.com/apple-oss-distributions/libffi/blob/libffi-40/src/closures.c#L257

Someone upstream will need to provide insight into why ROOT is passing that dylib to linker.

---

One possibility is ROOT may be looking at loaded libraries and passing any that look like system paths.

This would lead to picking up incorrect dylibs that should not be directly linked. You can see this by checking lsof output when using Python's ctypes:

$ python3
>>> import ctypes

❯ lsof -p $(ps | grep '[P]ython' | awk '{print $1}') | grep /usr/ | awk '{print $9}'
/usr/lib/libffi-trampolines.dylib
/usr/lib/dyld

---

Your workaround likely injects brew libffi instead of Apple's libffi.

In most cases, Apple's libffi is preferred as it includes Apple Silicon fixes which haven't been merged into libffi code base, e.g.

• https://github.com/libffi/libffi/pull/621

$ brew install libffi
$ DYLD_LIBRARY_PATH=/opt/homebrew/opt/libffi/lib:$DYLD_LIBRARY_PATH python3
>>> import ctypes

❯ lsof -p $(ps | grep '[P]ython' | awk '{print $1}') | grep /usr/ | awk '{print $9}'
/usr/lib/dyld

❯ lsof -p $(ps | grep '[P]ython' | awk '{print $1}') | grep libffi | awk '{print $9}'
/opt/homebrew/Cellar/libffi/3.5.2/lib/libffi.8.dylib

[vepadulano]

Hi! I'm trying to investigate this issue. I tried ROOT both compiled on a MacOS machine as well as with the conda-forge distribution. None of the two show the symptomatic error that homebrew shows.

local build

$: sw_vers
ProductName:		macOS
ProductVersion:		15.7.4
BuildVersion:		24G517
$: git clone https://github.com/root-project/root
$: cmake -B build -S root
$: cmake --build build
$: PYTHONPATH=build/lib python3
Python 3.11.0 (v3.11.0:deaf509e8f, Oct 24 2022, 14:43:23) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import ROOT
>>> ROOT.gInterpreter.ProcessLine(".L test.C")
0
>>> ROOT.gInterpreter.ProcessLine("test()")
hello
0

conda-forge package

$: mamba create -n root-63804 root==6.38.04
$: mamba activate root-63804
(root-63804) $: python
Python 3.14.3 | packaged by conda-forge | (main, Feb  9 2026, 22:09:14) [Clang 20.1.8 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import ROOT
>>> ROOT.gInterpreter.ProcessLine(".L test.C+")
Info in <TMacOSXSystem::ACLiC>: creating shared library /private/tmp/test_C.so
0
>>> ROOT.gInterpreter.ProcessLine("test()")
Hello
0
>>> 
(root-63804) bash-3.2$ root --version
ROOT Version: 6.38.04
Built for macosxarm64 on Mar 12 2026, 21:20:16
From tags/6-38-04@6-38-04

It looks like the problem only appears for the homebrew distribution. Could you guide me through what I can do to further check differences between the other distributions of ROOT on MacOS and the homebrew one?

[vepadulano]

Actually, I found a way to reproduce the user issue locally. I compiled ROOT on a different MacOS machine, this time is MacOS 26.1:

$: sw_vers
ProductName:		macOS
ProductVersion:		26.1
BuildVersion:		25B78
$: python
>>> import ROOT
>>> ROOT.gInterpreter.ProcessLine(".L test.C+")
Info in <TUnixSystem::ACLiC>: creating shared library /private/tmp/test_C.so
ld: cannot link directly with 'libffi-trampolines.dylib' because product being built is not an allowed client of it
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
Error in <ACLiC>: Executing 'cd "/private/tmp" ; c++ -fPIC -c -g  -Wc++11-narrowing -Wsign-compare -Wsometimes-uninitialized -Wconditional-uninitialized -Wheader-guard -Warray-bounds -Wcomment -Wtautological-compare -Wstrncat-size -Wloop-analysis -Wbool-conversion -m64 -pipe -W -Woverloaded-virtual -fsigned-char -fsized-deallocation -fno-common -Qunused-arguments -pthread -stdlib=libc++ -std=c++17  -I/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/include -isysroot "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk" -I"/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/etc/" -I"/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/etc//cling" -I"/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/etc//cling/plugins/include" -I"/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/include" -I"/opt/homebrew/include" -I"/opt/homebrew/opt/python@3.14/Frameworks/Python.framework/Versions/3.14/include/python3.14"   -D__ACLIC__ "/private/tmp/test_C_ACLiC_dict.cxx" ; c++ -g  "/private/tmp/test_C_ACLiC_dict.o" -dynamiclib -Wl,-w -Wl,-undefined,dynamic_lookup -Wl,-headerpad_max_install_names -m64 -Wl,-dead_strip_dylibs -Wl,-install_name,@rpath/test_C.so  -Wl,-rpath,/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib -Wl,-rpath,/private/tmp  "/opt/homebrew/Cellar/python@3.14/3.14.2/Frameworks/Python.framework/Versions/3.14/Python" "/usr/lib/libffi-trampolines.dylib" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/cppyy/libcppyy.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libCPyCppyy.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libCore.so" "/opt/homebrew/Cellar/xxhash/0.8.3/lib/libxxhash.0.8.3.dylib" "/opt/homebrew/Cellar/lz4/1.10.0/lib/liblz4.1.10.0.dylib" "/opt/homebrew/Cellar/zstd/1.5.7_1/lib/libzstd.1.5.7.dylib" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libRIO.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libThread.so" "/opt/homebrew/Cellar/tbb/2022.2.0/lib/libtbb.12.16.dylib" "/opt/homebrew/Cellar/tbb/2022.2.0/lib/libtbbmalloc.2.16.dylib" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libCling.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/ROOT/libROOTPythonizations.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libTree.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libImt.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libNet.so" "/Users/vpadulan/Programs/rootproject/rootbuild/master-319a37ec9e1-distrdf-debug/lib/libMultiProc.so" -o "/private/tmp/test_C.so" ' failed!

So now I have something to debug locally, will update this issue in case there are news 👍