std.process.Child: prevent racing children from inheriting one another's pipes #20075
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…r's pipes The added comment explains the issue here relatively well. The new progress API made this bug obvious because it became visibly clear that certain Compile steps were seemingly "hanging" until other steps completed. As it turned out, these child processes had raced to spawn, and hence one had inherited the other's stdio pipes, meaning the `poll` call in `std.Build.Step.evalZigProcess` was not identifying the child stdout as closed until an unrelated process terminated.
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This is @mlugg's commit from #20059 rebased to work on master branch + #20049.
The added comment explains the issue here relatively well. The new
progress API made this bug obvious because it became visibly clear that
certain Compile steps were seemingly "hanging" until other steps
completed. As it turned out, these child processes had raced to spawn,
and hence one had inherited the other's stdio pipes, meaning the
pollcall in
std.Build.Step.evalZigProcesswas not identifying the childstdout as closed until an unrelated process terminated.