[llvm-bugs] [Bug 32064] New: __atomic_is_lock_free incompatible with GCC

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https://bugs.llvm.org/show_bug.cgi?id=32064

            Bug ID: 32064
           Summary: __atomic_is_lock_free incompatible with GCC
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: t.p.northover at gmail.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

The pre-C11 function, __atomic_is_lock_free takes a second argument that
determines the alignment of the type/value in some way.

GCC appears to do this by looking at the value and libstdc++ passes "(void
*)-alignof(Type)". Clang, however, looks at the alignment of the pointee type
("void" in this case).

This results in a real libcall, which may not actually be available (I think).
Either way, it's not what GCC does.

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