python3x: -Wno-unused-result in _sysconfigdata__darwin_darwin.py unrecognized by gcc 4.2

[chrstphrchvz (Christopher Chavez)]

python37, python38, and python39 ports build using -Wno-unused-result; this argument gets saved in CFLAGS and other variables in _sysconfigdata__darwin_darwin.py, and is used again when building ports for Python modules. On macOS 10.6, Python itself is built using an alternative compiler (e.g. MacPorts' clang 3.7 or clang 9.0) which recognizes -Wno-unused-result, but modules (e.g. py3x-cchardet) might try to build using a system compiler (e.g. gcc 4.2) which doesn't recognize the option:

/usr/bin/gcc-4.2 -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -isysroot/ -Isrc/ext/uchardet/src -I/opt/local/Library/Frameworks/Python.framework/Versions/3.9/include/python3.9 -c src/cchardet/_cchardet.cpp -o build/temp.macosx-10.6-x86_64-3.9/src/cchardet/_cchardet.o
cc1plus: error: unrecognized command line option "-Wno-unused-result"

Possibly related to #56458. (I personally am not using macOS 10.6.)

[kencu (Ken)]

other than bootstrapping, or a few ports needed to bootstrap clang-9.0, like clang-3.7, every build on 10.6.8 should be using clang-9.0 to build.

I think the question might be how could py3x-cchardet be using the ancient gcc-4.2 and let's fix that if possible.

(I am using 10.6, all day, every day, and have never seen any such error with thousands of ports installed, by the way.)

[chrstphrchvz (Christopher Chavez)]

py38-fann2 is another example:

/usr/bin/gcc-4.2 -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -isysroot/ -DSWIG_COMPILE -I./include -I../include -Iinclude -I/opt/local/Library/Frameworks/Python.framework/Versions/3.8/include/python3.8 -c fann2/fann2_wrap.cxx -o build/temp.macosx-10.6-x86_64-3.8/fann2/fann2_wrap.o
cc1plus: error: unrecognized command line option "-Wno-unused-result"

Replying to kencu:

other than bootstrapping, or a few ports needed to bootstrap clang-9.0, like clang-3.7, every build on 10.6.8 should be using clang-9.0 to build.

Why is this not the case on the 10.6 builders?

[chrstphrchvz (Christopher Chavez)]

python39 is affected; python35 and python36 are not affected.

py37-pycryptodome and py38-pycryptodome are additional examples of ports failing to build on 10.6 because of this issue.

[chrstphrchvz (Christopher Chavez)]

In 2e5437a827f9ce39f7322bbcf00b7ca6f0063998/macports-ports (master):

py-cchardet: drop noarch, workaround GCC error

Port installs architecture-specific shared library built from
Cythonized code.

Avoid unrecognized command line option "-Wno-unused-result" error
See: #61299

py27-cchardet: fix distname

[kencu (Ken)]

I see that you pushed this through, although you don't use 10.6 or any older systems, you say.

blacklisting all gcc compilers is not the right fix for this problem.

[jmroot (Joshua Root)]

Just removing noarch would have caused the right compiler to be picked.

[kencu (Ken)]

Chris -- can you fix these again please?

[chrstphrchvz (Christopher Chavez)]

Replying to jmroot:

Just removing noarch would have caused the right compiler to be picked.

Thanks for pointing this out. Even though the examples I noticed so far all used noarch inappropriately, that being the cause of this issue was not obvious to me. I'm fine with this being closed.

[chrstphrchvz (Christopher Chavez)]

In 2fcfce40f95637821c0a5c286eeb5097bd640dfd/macports-ports (master):

py-cchardet: do not blacklist compilers (​https://github.com/macports/macports-ports/pull/8722)

Removing noarch was sufficient
See: #61299#comment:7

[kencu (Ken)]

thank you