[llvm-bugs] [Bug 30581] New: Inconsistent value of ATOMIC_LLONG_LOCK_FREE vs __atomic_always_lock_free(sizeof(long long), 0) on 32-bit x86

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30581

            Bug ID: 30581
           Summary: Inconsistent value of ATOMIC_LLONG_LOCK_FREE vs
                    __atomic_always_lock_free(sizeof(long long), 0) on
                    32-bit x86
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: mgorny at gentoo.org
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Consider the following test program:

  #include <iostream>

  int main()
  {
    // for comparison
    std::cerr << __GCC_ATOMIC_LONG_LOCK_FREE << std::endl;
    std::cerr << __atomic_always_lock_free(sizeof(long), 0) << std::endl;
    std::cerr << __GCC_ATOMIC_LLONG_LOCK_FREE << std::endl;
    std::cerr << __atomic_always_lock_free(sizeof(long long), 0) << std::endl;

    return 0;
  }


$ clang++ -m32 test.cxx
$ ./a.out 
2
1
1
1


So, ATOMIC_LLONG_LOCK_FREE indicates that the time is *sometimes* lock-free yet
__atomic_always_lock_free() indicates it's *always* lock-free.

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