diff options
| -rw-r--r-- | library/std/src/sys/windows/process.rs | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/library/std/src/sys/windows/process.rs b/library/std/src/sys/windows/process.rs index aff1b1c15ca..cc29d1a72fb 100644 --- a/library/std/src/sys/windows/process.rs +++ b/library/std/src/sys/windows/process.rs @@ -527,10 +527,25 @@ impl Stdio { }, Stdio::MakePipe => { - // If stdin then make synchronous + // Handles that are passed to a child process must be synchronous + // because they will be read synchronously (see #95759). + // Therefore we prefer to make both ends of a pipe synchronous + // just in case our end of the pipe is passed to another process. + // + // However, we may need to read from both the child's stdout and + // stderr simultaneously when waiting for output. This requires + // async reads so as to avoid blocking either pipe. + // + // The solution used here is to make handles synchronous + // except for our side of the stdout and sterr pipes. + // If our side of those pipes do end up being given to another + // process then we use a "pipe relay" to synchronize access + // (see `Stdio::AsyncPipe` below). let pipes = if stdio_id == c::STD_INPUT_HANDLE { + // For stdin both sides of the pipe are synchronous. Pipes::new_synchronous(false, true)? } else { + // For stdout/stderr our side of the pipe is async and their side is synchronous. pipe::anon_pipe(true, true)? }; *pipe = Some(pipes.ours); @@ -567,6 +582,9 @@ impl Stdio { impl From<AnonPipe> for Stdio { fn from(pipe: AnonPipe) -> Stdio { + // Note that it's very important we don't give async handles to child processes. + // Therefore if the pipe is asynchronous we must have a way to turn it synchronous. + // See #95759. match pipe { AnonPipe::Sync(handle) => Stdio::Handle(handle), AnonPipe::Async(handle) => Stdio::AsyncPipe(handle), |