py-libxml2, py-Pillow, py-gdbm: need to either blacklist gcc-4* or patch out -Wno-unused-result

[barracuda156]

gcc-4.2 does not understand this flag, and the build fails.

creating build/temp.macosx-10.6-ppc-cpython-310
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/compwrap/cc/usr/bin/gcc-4.2 -Wno-unused-result -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -arch ppc -isysroot/ -D_REENTRANT=1 -I/opt/local/include/libxml2 -I/opt/local/Library/Frameworks/Python.framework/Versions/3.10/include/python3.10 -c libxml.c -o build/temp.macosx-10.6-ppc-cpython-310/libxml.o
cc1: error: unrecognized command line option "-Wno-unused-result"
error: command '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/compwrap/cc/usr/bin/gcc-4.2' failed with exit code 1
Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/libxml2-2.9.14/python" && /opt/local/Library/Frameworks/Python.framework/Versions/3.10/bin/python3.10 setup.py --no-user-cfg build -j4 
Exit code: 1
Error: Failed to build py310-libxml2: command execution failed

Same for py-cython:

/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py310-cython/work/compwrap/cc/usr/bin/gcc-4.2 -Wno-unused-result -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -m64 -arch ppc -arch ppc64 -isysroot/ -I/opt/local/Library/Frameworks/Python.framework/Versions/3.10/include/python3.10 -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py310-cython/work/Cython-0.29.29/Cython/Plex/Scanners.c -o build/temp.macosx-10.5-ppc64-cpython-310/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py310-cython/work/Cython-0.29.29/Cython/Plex/Scanners.o
cc1: error: unrecognized command line option "-Wno-unused-result"
cc1: error: unrecognized command line option "-Wno-unused-result"
fatal error: lipo: can't open input file: /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py310-cython/work/.tmp/cc6ta5kY.out (No such file or directory)
error: command '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-cython/py310-cython/work/compwrap/cc/usr/bin/gcc-4.2' failed with exit code 1
* Getting dependencies for wheel...
* Building wheel...

ERROR Backend subproccess exited when trying to invoke build_wheel

[barracuda156]

It fails for x86_64 too:

creating build/lib.macosx-10.6-x86_64-cpython-310
copying libxml2.py -> build/lib.macosx-10.6-x86_64-cpython-310
copying drv_libxml2.py -> build/lib.macosx-10.6-x86_64-cpython-310
running build_ext
building 'libxml2mod' extension
creating build/temp.macosx-10.6-x86_64-cpython-310
/opt/x86_64/var/macports/build/_opt_x86_64_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/compwrap/cc/usr/bin/gcc-4.2 -Wno-unused-result -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -arch x86_64 -isysroot/ -D_REENTRANT=1 -I/opt/x86_64/include/libxml2 -I/opt/x86_64/Library/Frameworks/Python.framework/Versions/3.10/include/python3.10 -c libxml.c -o build/temp.macosx-10.6-x86_64-cpython-310/libxml.o
cc1: error: unrecognized command line option "-Wno-unused-result"
error: command '/opt/x86_64/var/macports/build/_opt_x86_64_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/compwrap/cc/usr/bin/gcc-4.2' failed with exit code 1
Command failed:  cd "/opt/x86_64/var/macports/build/_opt_x86_64_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/work/libxml2-2.9.14/python" && /opt/x86_64/Library/Frameworks/Python.framework/Versions/3.10/bin/python3.10 setup.py --no-user-cfg build -j4 
Exit code: 1
Error: Failed to build py310-libxml2: command execution failed
Error: See /opt/x86_64/var/macports/logs/_opt_x86_64_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_python_py-libxml2/py310-libxml2/main.log for details.

[reneeotten (Renee Otten)]

py-cython has blacklisted old gcc version in this commit

[kencu (Ken)]

is it somewhere in py-cython that where the flag Wno-unused-result originates? I have not as yet been able to see exactly where that flag gets thrown in, but it's some python build support port I guess.

blacklisting older compilers is one way around this, but TBH it is not really a great way around it, as that can then come back to bite you when you are no longer able to bootstrap any more.

Sometimes it's the only way out, though.

[barracuda156]

Replying to kencu:

is it somewhere in py-cython that where the flag Wno-unused-result originates? I have not as yet been able to see exactly where that flag gets thrown in, but it's some python build support port I guess.

blacklisting older compilers is one way around this, but TBH it is not really a great way around it, as that can then come back to bite you when you are no longer able to bootstrap any more.

Sometimes it's the only way out, though.

If it is thrown in by some build dependency, then patching it out should be easy enough. If not, then patching it out of every single port that uses it, I guess, is out of possibility, practically.

[barracuda156]

Replying to reneeotten:

py-cython has blacklisted old gcc version in this commit

The problem still exists for py-libxml2 and few other ports.

[jmroot (Joshua Root)]

Replying to kencu:

is it somewhere in py-cython that where the flag Wno-unused-result originates? I have not as yet been able to see exactly where that flag gets thrown in, but it's some python build support port I guess.

The mystery was solved via ​https://github.com/macports/macports-ports/pull/16064.

[kencu (Ken)]

worth noting that the entire point of building python with a newer gcc, to get LTO on PPC, that led to this is flawed as there is no LTO for PPC code on Darwin.

ld64 doesn’t support gcc’s LTO according to Iain.

​https://github.com/iains/darwin-toolchains-start-here/discussions/37#discussioncomment-3285847