Martin Weinelt
2ba40b5669
We run pytest with `--forked` in nixpkgs, to reduce side effects that can occur when multiple tests mutate their environment in incompatible ways. Forking on macOS 10.13 and later is unsafe when an application does work between calls to fork() and its followup exec(). This may lead to crashes when calls into the Objective-C runtime are issued, which will in turn coredump the Python interpreter. One good reproducer for this scenario is when the urllib module tries to lookup proxy configurations in `urllib.request.getproxies()` through `get_proxies_macos_sysconf` into the native `_scproxy` module. This is a class of issues that is of course not limited to the urllib module. The general recommendation is to use `spawn` instead of `fork`, but we don't have any influence on upstream developers to do one or the other. One often cited workaround would be to disable fork safety entirely on calls to `initialize()`, which is probably a better solution than running without multithreading (slow) or without the `--forked` (prone to side effects) mode. This currently happens on aarch64-linux only, where we use more recent 11.0 SDK version, while x86_64-darwin has been stuck on 10.12 for a while now. https://github.com/python/cpython/issues/77906#issuecomment-1093788352 http://www.sealiesoftware.com/blog/archive/2017/6/5/Objective-C_and_fork_in_macOS_1013.html Closes: #194290
27 lines
946 B
Bash
27 lines
946 B
Bash
pytestXdistHook() {
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pytestFlagsArray+=(
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"--numprocesses=$NIX_BUILD_CORES"
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"--forked"
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)
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# Using --forked on darwin leads to crashes when fork safety is
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# enabled. This often happens when urllib tries to request proxy
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# settings on MacOS through `urllib.request.getproxies()`
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# - https://github.com/python/cpython/issues/77906
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if [[ "$OSTYPE" == "darwin"* ]]; then
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export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
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fi
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}
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# the flags should be added before pytestCheckHook runs so
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# until we have dependency mechanism in generic builder, we need to use this ugly hack.
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if [ -z "${dontUsePytestXdist-}" ] && [ -z "${dontUsePytestCheck-}" ]; then
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if [[ " ${preDistPhases:-} " =~ " pytestCheckPhase " ]]; then
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preDistPhases+=" "
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preDistPhases="${preDistPhases/ pytestCheckPhase / pytestXdistHook pytestCheckPhase }"
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else
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preDistPhases+=" pytestXdistHook"
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fi
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fi
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