[PATCH] D81525: [Support] Ensure errs() is constructed after outs() and don't rerun tie when errs() is called

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 269864.
MaskRay retitled this revision from "[Support] Initialize outs() errs() nulls() once" to "[Support] Ensure errs() is constructed after outs() and don't rerun tie when errs() is called".
MaskRay edited the summary of this revision.
MaskRay added a comment.

Avoid global constructors

Add comments from labath


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D81525/new/

https://reviews.llvm.org/D81525

Files:
  llvm/lib/Support/raw_ostream.cpp


Index: llvm/lib/Support/raw_ostream.cpp
===================================================================
--- llvm/lib/Support/raw_ostream.cpp
+++ llvm/lib/Support/raw_ostream.cpp
@@ -876,10 +876,17 @@
 }
 
 raw_fd_ostream &llvm::errs() {
-  // Set standard error to be unbuffered and tied to outs() by default.
-  static raw_fd_ostream S(STDERR_FILENO, false, true);
-  S.tie(&outs());
-  return S;
+  // Ensure outs() is constructed before the unbuffered stderr stream so that
+  // outs() will be destructed after outs() and the TiedStream field of Init.S
+  // will not become dangling. The tie call is called once, thus the user can
+  // opt out the behavior.
+  static struct InitializeAndTie {
+    raw_fd_ostream S;
+    InitializeAndTie(raw_ostream &TieTo) : S(STDERR_FILENO, false, true) {
+      S.tie(&TieTo);
+    }
+  } Init(outs());
+  return Init.S;
 }
 
 /// nulls() - This returns a reference to a raw_ostream which discards output.


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