Python 3.8 doesn't build on 11.0

[mistydemeo]

• ran brew update and can still reproduce the problem?
• ran brew doctor, fixed all issues and can still reproduce the problem?
• ran brew gist-logs <formula> (where <formula> is the name of the formula that failed) and included the output link?
• if brew gist-logs didn't work: ran brew config and brew doctor and included their output with your issue?

What you were trying to do (and why)

python@3.8 was in the dependency tree of software I was installing, but failed to build from source on Big Sur.

What happened (include command output)

Installation fails; logs here: https://gist.github.com/mistydemeo/658ea7401c00b2b8dccee9f067ac2c0e

Specifically, the error is here:

clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.16.sdk -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.16.sdk/usr/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX10.16.sdk/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers   -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration  -I./Include/internal  -I. -I./Include    -DPy_BUILD_CORE_BUILTIN  -DPy_BUILD_CORE_BUILTIN -I./Include/internal -c ./Modules/posixmodule.c -o Modules/posixmodule.o
./Modules/posixmodule.c:9141:20: error: variable has incomplete type 'struct sf_hdtr'
    struct sf_hdtr sf;
                   ^
./Modules/posixmodule.c:9141:12: note: forward declaration of 'struct sf_hdtr'
    struct sf_hdtr sf;
           ^
1 error generated.

This happened on macOS 11.0 beta 1 for Intel using the CLT.

What you expected to happen

Build succeeds.

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

1. brew install python@3.8

[soheil]

This is also causing brew install node to fail since python 3.8 is a dependency.

[soheil]

PR to remove python 3.8 dependency for node #56795

[claui]

A little info about struct sf_hdtr: man sendfile

[goranmoomin]

In fact, this applies to usual python as well.

[Bo98]

This is being handled upstream. It's still early days of the beta.

[claui]

This is being handled upstream.

@Bo98 Are you referring to python/cpython#21113?

[Bo98]

Ah yes. I wasn't aware that the pull request had already been created so I didn't have anything to link.

That indeed should fix the issue.

[ndaemy]

Is there any way to fix this problem temporary?

[claui]

Is there any way to fix this problem temporary?

Nothing that Homebrew would be able to support.
I’m afraid you’re on your own here. But as @Bo98 said: please remember that macOS BS is in a very early beta.
Issues like the one at hand are to be expected.

[Bo98]

If you have Homebrew installed to /usr/local, then the existing Catalina bottles can be used and thus you do not need to worry about the build issues.

We may apply upstream's patch to the formula once it is merged.

But please try to get used to there being issues in the Big Sur betas. Python is not the only thing broken (CMake is another, for example) and we already know that there will be further breakages as the betas progress (such as 10.16 becoming 11.0).

[mistydemeo]

Can confirm that PR will fix it; I'll backport that to us once it's merged upstream, but we can hold out until then.

[Bo98]

The patch managed to just sneak in to 3.7.8 which will be released in the next few days.

We can apply python/cpython#21154 for 3.8 until 3.8.4 releases in mid-July.