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+++ This bug was initially created as a clone of Bug #2034494 +++

LLVM currently hard-codes the size of struct pthread in the sanitizers, in ThreadDescriptorSize in compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp.

Starting with glibc 2.34 and this commit

commit fef400a2f976d1fd6a4639e6980f6c50ee13fbf5
Author: Florian Weimer <fweimer>
Date:   Mon Jun 28 14:33:53 2021 +0200

    nptl: Export libthread_db-used symbols under GLIBC_PRIVATE
    
    This allows distributions to strip debugging information from
    libc.so.6 without impacting the debugging experience.
    
    Reviewed-by: Carlos O'Donell <carlos>

it is possible to determine sizeof (struct pthread) using dl(v)sym, like this:

  const unsigned int *psize = dlvsym(RTLD_DEFAULT, "_thread_db_sizeof_pthread",
                                     "GLIBC_PRIVATE");
  if (psize != nullptr) {
    val = *psize;
    atomic_store_relaxed(&thread_descriptor_size, val);
    return val;
  }

I'm not sure if upstream will take this change, but we should definitely make it downstream, to avoid mysterious sanitizer problems if we need to change struct pthread in glibc.

Upstream patch review: https://reviews.llvm.org/D119007