[all-commits] [llvm/llvm-project] 030897: [Support] Don't tie errs() to outs() by default

[Fangrui Song via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 030897523d43e3296f69d25a71a140d9e5793c6a
      https://github.com/llvm/llvm-project/commit/030897523d43e3296f69d25a71a140d9e5793c6a
  Author: Fangrui Song <maskray at google.com>
  Date:   2020-06-11 (Thu, 11 Jun 2020)

  Changed paths:
    M llvm/lib/Support/raw_ostream.cpp
    M llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp

  Log Message:
  -----------
  [Support] Don't tie errs() to outs() by default

This reverts part of D81156.

Accessing errs() concurrently was safe before and racy after D81156.
(`errs() << 'a'` is always racy)

Accessing outs() and errs() concurrently was safe before and racy after D81156.

Don't tie errs() to outs() by default to fix the fallout.
llvm-dwarfdump is single-threaded and opting in the tie behavior is safe.