Install libffi-dev to fix xKAN-meta_testing Docker image build

[DasSkelett]

Problem

For an unknown reason, the Docker build for the xKAN-meta_testing / metadata image stopped working today, with the following error:

Running setup.py install for cffi: started
    Running setup.py install for cffi: finished with status 'error'
    Complete output from command /usr/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-install-dgjvercc/cffi/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-record-ck490wkh/install-record.txt --single-version-externally-managed --compile:
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-3.7
    creating build/lib.linux-x86_64-3.7/cffi
    copying cffi/pkgconfig.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/error.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/lock.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/ffiplatform.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/cparser.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/__init__.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/setuptools_ext.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/recompiler.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/commontypes.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/backend_ctypes.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/api.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/model.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/vengine_cpy.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/vengine_gen.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/verifier.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/cffi_opcode.py -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/_cffi_include.h -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/parse_c_type.h -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/_embedding.h -> build/lib.linux-x86_64-3.7/cffi
    copying cffi/_cffi_errors.h -> build/lib.linux-x86_64-3.7/cffi
    running build_ext
    building '_cffi_backend' extension
    creating build/temp.linux-x86_64-3.7
    creating build/temp.linux-x86_64-3.7/c
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -DUSE__THREAD -DHAVE_SYNC_SYNCHRONIZE -I/usr/include/ffi -I/usr/include/libffi -I/usr/include/python3.7m -c c/_cffi_backend.c -o build/temp.linux-x86_64-3.7/c/_cffi_backend.o
    c/_cffi_backend.c:15:10: fatal error: ffi.h: No such file or directory
     #include <ffi.h>
              ^~~~~~~
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    
    ----------------------------------------
Command "/usr/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-install-dgjvercc/cffi/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-record-ck490wkh/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-install-dgjvercc/cffi/

(Full output at https://github.com/KSP-CKAN/CKAN/runs/3915298469?check_suite_focus=true)

The error message talks about a libffi missing. Wikipedia says this library is used "as a bridging technology between compiled and interpreted language implementations", like Python.

No idea why this appears only now, my suspicion is something must've changed upstream in Debian. However I couldn't find any recently changed Python package.

Changes

Turns out, installing the libffi-dev package fixes it, at least in a local test run. I also tried libffi6, which didn't work as I suspect it requires the header files, usually only present in -dev packages.

[HebaruSan]

Maybe the underlying Debian images used to have libffi-dev installed by default and now they don't?

[DasSkelett]

Maybe the underlying Debian images used to have libffi-dev installed by default and now they don't?

Looking at the changes of the recent Debian Docker image update, there are quite a few lines mentioning libffi, it appears it has been updated from version 7 to 8. But only for Bookworm/testing, not Buster, which is the current base for Mono images.

docker-library/official-images#11087 (comment)

But maybe not all changes to the rootfs are visible there.