buildbot failure in LLVM on llvm-clang-x86_64-expensive-checks-ubuntu

[Evgeny Leviant via llvm-commits]

I've investigated this and it seems we have issue in APInt move ctor:

#ifdef EXPENSIVE_CHECKS
    // Some std::shuffle implementations still do self-assignment.
    if (this == &that)
      return *this;
#endif
    assert(this != &that && "Self-move not supported");

It seems that libstdc++ implementation of std::shuffle may also do self
assignment. Here is a piece from iter_swap:

  if ((__urange % 2) == 0)
  {
    __distr_type __d{0, 1};
    std::iter_swap(__i++, __first + __d(__g));
  }

Here __g is a uniformly distributed random value. When size of a range
is 2 possibility of __i being equal to __first + __d(__g) is 50%

This is reproducible on Ubuntu 18.04.
________________________________________
От: llvm.buildmaster at lab.llvm.org <llvm.buildmaster at lab.llvm.org>
Отправлено: 20 августа 2020 г. 13:10
Кому: David Stenberg; Evgeny Leviant; George Rimar
Копия: gkistanova at gmail.com
Тема: buildbot failure in LLVM on llvm-clang-x86_64-expensive-checks-ubuntu

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The Buildbot has detected a new failure on builder llvm-clang-x86_64-expensive-checks-ubuntu while building llvm.
Full details are available at:
 http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-ubuntu/builds/8341

Buildbot URL: http://lab.llvm.org:8011/

Buildslave for this Build: as-builder-4

Build Reason: scheduler
Build Source Stamp: [branch master] 455d5a8a065b4b93df11d1696dc1546c403465a5
Blamelist: David Stenberg <david.stenberg at ericsson.com>,Evgeny Leviant <eleviant at accesssoftek.com>,Georgii Rymar <grimar at accesssoftek.com>

BUILD FAILED: failed test-check-all

sincerely,
 -The Buildbot