Optimize some functions in std::process #31618
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☔ The latest upstream changes (presumably #31825) made this pull request unmergeable. Please resolve the merge conflicts. |
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☔ The latest upstream changes (presumably #31858) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors r+ Glad to see that thread go. |
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💔 Test failed - auto-win-msvc-64-opt |
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bors
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Mar 10, 2016
Optimize some functions in std::process * Be sure that `read_to_end` gets directed towards `read_to_end_uninitialized` for all handles * When spawning a child that guaranteed doesn't need a stdin, don't actually create a stdin pipe for that process, instead just redirect it to /dev/null * When calling `wait_with_output`, don't spawn threads to read out the pipes of the child. Instead drain all pipes on the calling thread and *then* wait on the process. Functionally, it is intended that nothing changes as part of this PR --- Note that this was the same as #31613, and even after that it turned out that fixing Windows was easier than I thought! To copy a comment from over there: > As some rationale for this as well, it's always bothered me that we've spawned threads in the standard library for this (seems a bit overkill), and I've also been curious lately as to our why our build times for Windows are so much higher than Unix (on the buildbots we have). I have done basically 0 investigation into why, but I figured it can't help to try to optimize Command::output which I believe is called quite a few times during the test suite.
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alexcrichton
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This regression was accidentally introduced in rust-lang#31618, and it's just flipping a boolean! Closes rust-lang#32254
This was referenced Mar 15, 2016
Manishearth
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…uron std: Fix inheriting stdin on status() This regression was accidentally introduced in rust-lang#31618, and it's just flipping a boolean! Closes rust-lang#32254
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…uron std: Fix inheriting stdin on status() This regression was accidentally introduced in rust-lang#31618, and it's just flipping a boolean! Closes rust-lang#32254
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This commit fixes a mistake introduced in rust-lang#31618 where overlapped handles were leaked to child processes on Windows. On Windows once a handle is in overlapped mode it should always have I/O executed with an instance of `OVERLAPPED`. Most child processes, however, are not prepared to have their stdio handles in overlapped mode as they don't use `OVERLAPPED` on reads/writes to the handle. Now we haven't had any odd behavior in Rust up to this point, and the original bug was introduced almost a year ago. I believe this is because it turns out that if you *don't* pass an `OVERLAPPED` then the system will [supply one for you][link]. In this case everything will go awry if you concurrently operate on the handle. In Rust, however, the stdio handles are always locked, and there's no way to not use them unlocked in libstd. Due to that change we've always had synchronized access to these handles, which means that Rust programs typically "just work". Conversely, though, this commit fixes the test case included, which exhibits behavior that other programs Rust spawns may attempt to execute. Namely, the stdio handles may be concurrently used and having them in overlapped mode wreaks havoc. [link]: https://blogs.msdn.microsoft.com/oldnewthing/20121012-00/?p=6343 Closes rust-lang#38811
nikomatsakis
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Jan 6, 2017
This commit fixes a mistake introduced in rust-lang#31618 where overlapped handles were leaked to child processes on Windows. On Windows once a handle is in overlapped mode it should always have I/O executed with an instance of `OVERLAPPED`. Most child processes, however, are not prepared to have their stdio handles in overlapped mode as they don't use `OVERLAPPED` on reads/writes to the handle. Now we haven't had any odd behavior in Rust up to this point, and the original bug was introduced almost a year ago. I believe this is because it turns out that if you *don't* pass an `OVERLAPPED` then the system will [supply one for you][link]. In this case everything will go awry if you concurrently operate on the handle. In Rust, however, the stdio handles are always locked, and there's no way to not use them unlocked in libstd. Due to that change we've always had synchronized access to these handles, which means that Rust programs typically "just work". Conversely, though, this commit fixes the test case included, which exhibits behavior that other programs Rust spawns may attempt to execute. Namely, the stdio handles may be concurrently used and having them in overlapped mode wreaks havoc. [link]: https://blogs.msdn.microsoft.com/oldnewthing/20121012-00/?p=6343 Closes rust-lang#38811
bors
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std: Don't pass overlapped handles to processes This commit fixes a mistake introduced in #31618 where overlapped handles were leaked to child processes on Windows. On Windows once a handle is in overlapped mode it should always have I/O executed with an instance of `OVERLAPPED`. Most child processes, however, are not prepared to have their stdio handles in overlapped mode as they don't use `OVERLAPPED` on reads/writes to the handle. Now we haven't had any odd behavior in Rust up to this point, and the original bug was introduced almost a year ago. I believe this is because it turns out that if you *don't* pass an `OVERLAPPED` then the system will [supply one for you][link]. In this case everything will go awry if you concurrently operate on the handle. In Rust, however, the stdio handles are always locked, and there's no way to not use them unlocked in libstd. Due to that change we've always had synchronized access to these handles, which means that Rust programs typically "just work". Conversely, though, this commit fixes the test case included, which exhibits behavior that other programs Rust spawns may attempt to execute. Namely, the stdio handles may be concurrently used and having them in overlapped mode wreaks havoc. [link]: https://blogs.msdn.microsoft.com/oldnewthing/20121012-00/?p=6343 Closes #38811
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read_to_endgets directed towardsread_to_end_uninitializedfor all handleswait_with_output, don't spawn threads to read out the pipes of the child. Instead drain all pipes on the calling thread and then wait on the process.Functionally, it is intended that nothing changes as part of this PR
Note that this was the same as #31613, and even after that it turned out that fixing Windows was easier than I thought! To copy a comment from over there: