Avoid retaining all rustc output in memory.

src/cargo/core/compiler/job_queue.rs

@@ -113,7 +113,7 @@ impl<'a> JobState<'a> {
  &self,
  cmd: &ProcessBuilder,
  prefix: Option<String>,
- print_output: bool,
+ capture_output: bool,
  ) -> CargoResult<Output> {
  let prefix = prefix.unwrap_or_else(|| String::new());
  cmd.exec_with_streaming(
@@ -125,7 +125,7 @@ impl<'a> JobState<'a> {
  let _ = self.tx.send(Message::Stderr(format!("{}{}", prefix, err)));
  Ok(())
  },
- print_output,
+ capture_output,
  )
  }
 }

src/cargo/util/process_builder.rs

@@ -202,7 +202,7 @@ impl ProcessBuilder {
  &self,
  on_stdout_line: &mut FnMut(&str) -> CargoResult<()>,
  on_stderr_line: &mut FnMut(&str) -> CargoResult<()>,
- print_output: bool,
+ capture_output: bool,
  ) -> CargoResult<Output> {
  let mut stdout = Vec::new();
  let mut stderr = Vec::new();
@@ -226,23 +226,33 @@ impl ProcessBuilder {
  None => return,
  }
  };
- let data = data.drain(..idx);
- let dst = if is_out { &mut stdout } else { &mut stderr };
- let start = dst.len();
- dst.extend(data);
- for line in String::from_utf8_lossy(&dst[start..]).lines() {
- if callback_error.is_some() {
- break;
- }
- let callback_result = if is_out {
- on_stdout_line(line)
+ { // scope for new_lines
+ let new_lines = if capture_output {
+ let dst = if is_out { &mut stdout } else { &mut stderr };
+ let start = dst.len();
+ let data = data.drain(..idx);
+ dst.extend(data);
+ &dst[start..]
  } else {
- on_stderr_line(line)
+ &data[..idx]
  };
- if let Err(e) = callback_result {
- callback_error = Some(e);
+ for line in String::from_utf8_lossy(new_lines).lines() {
+ if callback_error.is_some() {
+ break;
+ }
+ let callback_result = if is_out {
+ on_stdout_line(line)
+ } else {
+ on_stderr_line(line)
+ };
+ if let Err(e) = callback_result {
+ callback_error = Some(e);
+ }
  }
  }
+ if !capture_output {
+ data.drain(..idx);
+ }
  })?;
  child.wait()
  })()
@@ -260,7 +270,7 @@ impl ProcessBuilder {
  };
 
  {
- let to_print = if print_output { Some(&output) } else { None };
+ let to_print = if capture_output { Some(&output) } else { None };
  if !output.status.success() {
  return Err(process_error(
  &format!("process didn't exit successfully: {}", self),

tests/testsuite/support/mod.rs

@@ -770,7 +770,7 @@ impl Execs {
  process.exec_with_streaming(
  &mut |out| Ok(println!("{}", out)),
  &mut |err| Ok(eprintln!("{}", err)),
- false,
+ true,
  )
  } else {
  process.exec_with_output()