tree ef205286802df2674a4e78710c0fdedb04036f2c
parent 25d202fc1545f4aaba821df75a8bf3fb57284da1
author jmmv <jmmv@google.com> 1550763242 -0800
committer Copybara-Service <copybara-worker@google.com> 1550763344 -0800

Use posix_spawn to start the Bazel server.

Introduce a new "daemonize" helper tool that takes the heavy-lifting
of starting the Bazel server process as a daemon.  This tool is pure
C and does not have any big dependencies like gRPC so we can ensure
it's thread-free.  As a result, the code in this tool doesn't have
to take a lot of care when running fork(), which results in easier
to read code overall.

Then, change the Bazel client to simply use posix_spawn to invoke
this helper tool, which in turn runs the Bazel server as a daemon.
The code in the Bazel client becomes simpler as well as we don't
have to worry about the implications of using fork() from a threaded
process.

The switch to posix_spawn is necessary to address
https://github.com/bazelbuild/bazel/issues/7446 because the only way
to customize the QoS of a process in macOS is by using this API.
Such a change will come separately.

This change is intended to be a no-op.  However, this fixes a bug
introduced in unknown commit by which we violated the requirement of
not doing any memory management from a child process started with
fork().  (I don't think this bug ever manifested itself, but it was
there -- which is funny because this piece of code went to great
extents to not do the wrong thing... and a one-line change let
hell break loose.)

RELNOTES: None.
PiperOrigin-RevId: 234991943