Avoid allocating in pre_exec closure#340
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jamesmcm merged 1 commit intojamesmcm:masterfrom Nov 17, 2025
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Thanks, good catch! (and for documenting it upstream). This might also make a good Clippy lint. |
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// The closure now ONLY contains async-signal-safe syscall wrappers.is misleading, since allocations are not async-signal-safe. There are three sources of allocation:std::io::Error::other(see Document Error::{new,other} as to be avoided in pre_exec rust-lang/rust#148971)format!CString::newI've moved out
CString::newsimilarly to other strings, hopefully that's idiomatic for your project.Error::otherandformat!are trickier. Error messages are not transferred acrosspre_execboundary, so whatever error messages you wrote were never visible. I replaced error handling with?, which uses the non-allocatingimpl From<nix::Error> for std::io::Error, under assumption that if error messages weren't transmitted before, it's fine to ignore them now.Another possible alternative would be to use
.expect, effectively transmitting the error via stderr. I couldn't make a judgement on whether that's correct for use case, so I refrained from doing that.