Revert #131060 "Drop conditionally applied cargo -Zon-broken-pipe=kill flags"

[jieyouxu]

In #131059 we found out that -Zon-broken-pipe=kill is actually load-bearing¹ for
(at least) rustc and rustdoc to have the kill-process-on-broken-pipe behavior, e.g. rustc --print=sysroot | false will ICE and rustdoc --print=sysroot | false will panic on a broken pipe.

This PR reverts 5a7058c (reverts PR #131060) in favor of a future
fix to unconditionally apply -Zon-broken-pipe=kill to tool builds and also not drop the
-Zon-broken-pipe=kill flag for rustc binary builds.

I could not figure out how to write a regression test for the rustc --print=sysroot | false
behavior on Unix, so this is a plain revert for now.

This revert will unfortunately reintroduce #130980 until we fix it again with the different approach.

See more details at #131059 (comment) and in the timeline below.

Timeline of kill-process-on-broken-pipe behavior changes

See unix_sigpipe tracking issue #97889 for more context around unix sigpipe handling.

• From the very beginning since 2014, Rust binaries by default use sig_ign. This meant that if
  output pipe is broken yet the program tries to use println! and such, there will be a broken
  pipe panic from std. This lead to ICEs from e.g. rustc --help | false #34376.
• #49606 mitigated #34376 by adding an explicit signal handler to rustc_driver register a
  sigpipe handler with SIG_DFL which will cause the binary using rustc_driver to terminate if
  rustc_driver::set_sigpipe_handler() is called. rustc's main binary wrapper uses
  rustc_driver::set_sigpipe_handler(), and so does rustdoc.
• A more universal way to set sigpipe behavior for Unix was introduced as part of #97889, i.e. # [unix_sigpipe = "sig_dfl"] attribute.
• #102587 migrated rustc to use #[unix_sigpipe = "sig_dfl"] instead of
  rustc_driver::set_sigpipe_handler.
• #103495 migrated rustdoc to use #[unix_sigpipe = "sig_dfl"] instead of
  rustc_driver::set_sigpipe_handler. rustc_driver::set_sigpipe_handler was removed.
• Following concerns about sigpipe setting UI in #97889, the UI for specifying sigpipe behavior
  was changed in #124480 from #[unix_sigpipe = "sig_dfl"] attribute to the commmand line flag
  -Zon-broken-pipe=kill.
  • In the same PR, #[unix_sigpipe = "sig_dfl"] were removed from rustc and rustdoc main
    binary crate entry points in favor of the command line flag. Kill-process-on-broken-pipe
    behavior was preserved by adding -Zon-broken-pipe=kill for rustdoc tool build step and
    rustc during compile steps.
• [fix broken build cache caused by rustdoc builds #126934] added -Zon-broken-pipe=kill for tool builds except for cargo to help with some miri
  tests because at the time the PR was written, this would lead to a couple of cargo test failures.
  Conditionally setting RUSTFLAGS can lead to tool build invalidation, e.g. building cargo
  without -Zon-broken-pipe=kill but clippy with the flag can lead to invalidation of the tool
  build cache. This is not a problem at the time, because nothing (not even miri) tests built stage
  1 cargo (all used initial cargo).
• In #130634 we found out that run-make tests like compiler-builtins needed stage 1 cargo, not
  just beta bootstrap cargo, because there can be changes that are present in stage 1 cargo but
  absent in beta cargo, which was blocking a beta backport.
• #130642 and later #130739 now build stage 1 cargo. And as previously mentioned, since
  -Zon-broken-pipe=kill was specifically not set for cargo, this caused tool build cache
  invalidation meaning rebuilds of stage 1 even if nothing in source was changed due to differing
  RUSTFLAGS since run-make also builds rustdoc and such #130980.

r? @onur-ozkan (or bootstrap)

Footnotes

1. https://github.com/rust-lang/rust/issues/131059#issuecomment-2385822033 ↩

[onur-ozkan]

@bors r+

[bors]

📌 Commit 1c7e824 has been approved by onur-ozkan

It is now in the queue for this repository.