[all-commits] [llvm/llvm-project] c6d95c: [libc++] Fix initialization-order-fiasco with iost...

[Vitaly Buka via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c6d95c441a29a45782ff72d6cb82839b86fd0e4a
      https://github.com/llvm/llvm-project/commit/c6d95c441a29a45782ff72d6cb82839b86fd0e4a
  Author: Vitaly Buka <vitalybuka at google.com>
  Date:   2025-02-15 (Sat, 15 Feb 2025)

  Changed paths:
    M libcxx/src/iostream.cpp
    A libcxx/test/std/input.output/iostreams.base/ios.base/ios.types/ios_Init/ios_Init.global.pass.cpp

  Log Message:
  -----------
  [libc++] Fix initialization-order-fiasco with iostream.cpp constructors (#126995)

Asan reports it after #124103.

It's know case of false positive for Asan.

https://github.com/google/sanitizers/wiki/AddressSanitizerInitializationOrderFiasco#false-positives

It's can be avoided with `constexpr` constructors.

In general order global constructors in different
modules is undefined. If global constructor uses
external global, they can be not constructed yet.

However, implementation may contain workaround for
that, or the state of non-constructed global can
be still valid.

Asan will still falsely report such cases, as it
has no machinery to detect correctness of such
cases.

We need to fix/workaround the issue in libc++, as
it will affect many libc++ with Asan users.



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