py-matplotlib: automated build failures on High Sierra, Mojave, Catalina

[thomasrussellmurphy (Thomas Russell Murphy)]

Current port health shows these three platforms failing from the last update: ​https://ports.macports.org/port/py39-matplotlib/details/

I'm also seeing a build failure locally on my 10.14.6 machine and can provide an additional log if desired.

[reneeotten (Renee Otten)]

It looks like the problem is:

building 'matplotlib.backends._macosx' extension
creating build/temp.macosx-10.14-x86_64-cpython-39/matplotlib.backends._macosx
creating build/temp.macosx-10.14-x86_64-cpython-39/matplotlib.backends._macosx/src
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_python_py-matplotlib/py39-matplotlib/work/compwrap/cc/usr/bin/clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -arch x86_64 -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -I/opt/local/Library/Frameworks/Python.framework/Versions/3.9/include/python3.9 -c src/_macosx.m -o build/temp.macosx-10.14-x86_64-cpython-39/matplotlib.backends._macosx/src/_macosx.o -Werror -fvisibility=hidden -flto
src/_macosx.m:48:49: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
static struct sigaction originalSigintAction = {0};
                                                ^
                                                {}
src/_macosx.m:61:42: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
        struct sigaction customAction = {0};
                                         ^
                                         {}
2 errors generated.

I cannot tell if this is really an error that should be fixed upstream (I kind of doubt it) or it's just something that some versions of Clang complain about... The latter case explains why it build on most systems, but not all.

I notice as well that the build is using -Werror as an flag/option, which is AFAIK not really we typically use in MacPorts. So I could/would look into where that is added in the build and just remove it or -perhaps better- replace it by -Wextra as is being done in some other ports.

I will take a look but cannot promise on when I'll get to it.

[thomasrussellmurphy (Thomas Russell Murphy)]

Thanks for your attention. This is a blocker to upgrading/installing gnuradio on the affected OSs and other radio-encoding/decoding related ports that still default to python39 ports.

[reneeotten (Renee Otten)]

In 6b60208ca52dc75b9c9ce8cd6bd85e9ccb689e02/macports-ports (master):

py-matplotlib: update to 3.8.2

• disable use of -Werror

Closes: #68710

[jmroot (Joshua Root)]

Replying to reneeotten:

I cannot tell if this is really an error that should be fixed upstream (I kind of doubt it) or it's just something that some versions of Clang complain about...

Doing what the warning suggests is a good idea for clarity, but like many other warnings, it's not something that will result in incorrect code behaviour. It would be nice to have an option to control the use of -Werror so upstream can keep using it when developing and in their CI builds, but leave it disabled by default for end user builds. If the idea hasn't already been brought up and rejected, it would be worth suggesting.