os/exec: Cmd.Wait Cmd.StderrPipe data-loss race condition go1.22.3 240525 darwin-arm64 14.5 about go

[haraldrudell]

I wrote a fast writer draining the OS-pipe within microseconds. Problem persists
— FastWriter receives many chunks, the longest 16,571 bytes, the large one in less than 118μs, smaller in less than 20μs
— FastWriter receives additional small chunks after the big chunk

Apple baselessly asserts macOS the best operating system in the world, where writing to a terminal window could erratically take 2 seconds

[ianlancetaylor]

This behavior is documented. See https://pkg.go.dev/os/exec#Cmd.StderrPipe. I'm not sure there is anything to do here.

[haraldrudell]

There is therefore an additional synchronizing wait required:
— in between successful [exec.Cmd.Start] and [exec.Cmd.Wait] where
— any stream obtained via [exec.Cmd.StderrPipe] [exec.Cmd.StdoutPipe] has to be read until io.EOF

the [exec.Cmd.Wait] subsequent to that does not await anything, it does cleanup

[haraldrudell]

worksforme