assert(header->exceptionDestructor == &deleteException);

#if defined _LIBCPPABI_VERSION // detect libc++abi

    // First, the libcxxabi commit

    // <http://llvm.org/viewvc/llvm-project?view=revision&revision=303175>

    // "[libcxxabi] Align unwindHeader on a double-word boundary" towards

    // LLVM 5.0 changed the size of __cxa_exception by adding

    //

    //   __attribute__((aligned))

    //

    // to the final member unwindHeader, on x86-64 effectively adding a hole of

    // size 8 in front of that member (changing its offset from 88 to 96,

    // sizeof(__cxa_exception) from 120 to 128, and alignof(__cxa_exception)

    // from 8 to 16); the "header1" hack below to dynamically determine whether we run against a

    // LLVM 5 libcxxabi is to look at the exceptionDestructor member, which must

    // point to this function (the use of __cxa_exception in fillUnoException is

    // unaffected, as it only accesses members towards the start of the struct,

    // through a pointer known to actually point at the start).  The libcxxabi commit

    // <https://github.com/llvm/llvm-project/commit/9ef1daa46edb80c47d0486148c0afc4e0d83ddcf>

    // "Insert padding before the __cxa_exception header to ensure the thrown" in LLVM 6

    // removes the need for this hack, so the "header1" hack can be removed again once we can be

    // sure that we only run against libcxxabi from LLVM >= 6.

    //

    // Second, the libcxxabi commit

    // <https://github.com/llvm/llvm-project/commit/674ec1eb16678b8addc02a4b0534ab383d22fa77>

    // "[libcxxabi] Insert padding in __cxa_exception struct for compatibility" in LLVM 10 changed

    // the layout of the start of __cxa_exception to

    //

    //  [8 byte  void *reserve]

    //   8 byte  size_t referenceCount

    //

    // so the "header2" hack below to dynamically determine whether we run against a LLVM >= 10

    // libcxxabi is to look whether the exceptionDestructor (with its known value) has increased its

    // offset by 8.  As described in the definition of __cxa_exception

    // (bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx), the "header2" hack (together with the

    // "#if 0" in the definition of __cxa_exception and the corresponding hack in fillUnoException)

    // can be dropped once we can be sure that we only run against new libcxxabi that has the

    // reserve member.

    if (header->exceptionDestructor != &deleteException) {

        auto const header1 = reinterpret_cast<__cxa_exception const *>(

            reinterpret_cast<char const *>(header) - 8);

        if (header1->exceptionDestructor == &deleteException) {

            header = header1;

        } else {

            auto const header2 = reinterpret_cast<__cxa_exception const *>(

                reinterpret_cast<char const *>(header) + 8);

            if (header2->exceptionDestructor == &deleteException) {

                header = header2;

            } else {

                assert(false);

            }

        }

    }

#endif

    assert(header->exceptionDestructor == &deleteException);