[llvm-bugs] [Bug 45549] New: std::type_index equality broken with LIBCPP_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45549

            Bug ID: 45549
           Summary: std::type_index equality broken with
                    LIBCPP_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF
           Product: libc++
           Version: 9.0
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ryan.brown at ableton.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com

When using LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF, distinct classes with
the same name, each in a different TU and anonymous namespace, are considered
equal by std::type_index.

LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF is used in the libc++ shipped with
Xcode as of Xcode 11.4. The bug does not occur in Xcode 11.3.1, the previous
version. LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT was introduced in 2405bd689
for LLVM 9.0.0.

See https://gist.github.com/ryb-ableton/1805b61e2d0976de4ba04c2aa2f5992b for a
minimal test case.

May be related to https://bugs.llvm.org/show_bug.cgi?id=34907

----------------

Steps to reproduce on Linux/x86:

  1. Build and install libc++ 9.0 or 10.0 by passing
-DLIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF to cmake
  2. Download and extract a zip of the Gist linked above
  3. Run "bash ./build_and_run"

Steps to reproduce on macOS:

  1. Install and select Xcode 11.4, which uses
LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT=OFF by default
  2. Download and extract a zip of the Gist linked above
  3. Run "bash ./build_and_run"

Actual Output:

  Assertion failed: (registry[0] != registry[1]), function main, file main.cpp,
line 13.
  ./run: line 4: 39942 Abort trap: 6           ./test
  Failure

Expected Output:

  Success

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