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Ensure that grandchildren cannot keep an exited child alive. - #152
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ltratt merged 1 commit intoSep 24, 2026
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snare previously only checked for a child's exit when its stderr and stdout were closed. This works fine except when the child has handed stderr's and/or stdout's file handles to grandchildren which have (for whatever reason) not exited. The fix is conceptually simple but has annoying details: we already use SIGCHLD to inform us when a (we don't know which!) child process has died. So we now use `try_wait` to see if a child has exited without worrying about whether stderr/stdout have `HUP`ed. That then means that there may be data in both file handles that we haven't read, which we need to deal with. But in the "grandchildren are alive" situation, reading from them may never reach EOF, so we only read the data that's available: fortunately, for the "normal" situation this does the right thing. While testing this I ran into a bug in rust + OpenBSD which it turns out is fixed in rust-nightly but not in 1.98.1, so I went down that rathole, and the fix for that ends up in here. Oh well.
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snare previously only checked for a child's exit when its stderr and stdout were closed. This works fine except when the child has handed stderr's and/or stdout's file handles to grandchildren which have (for whatever reason) not exited.
The fix is conceptually simple but has annoying details: we already use SIGCHLD to inform us when a (we don't know which!) child process has died. So we now use
try_waitto see if a child has exited without worrying about whether stderr/stdout haveHUPed. That then means that there may be data in both file handles that we haven't read, which we need to deal with. But in the "grandchildren are alive" situation, reading from them may never reach EOF, so we only read the data that's available: fortunately, for the "normal" situation this does the right thing.While testing this I ran into a bug in rust + OpenBSD which it turns out is fixed in rust-nightly but not in 1.98.1, so I went down that rathole, and the fix for that ends up in here. Oh well.