Saxon

Logged by T Hata in https://saxonica.plan.io/boards/3/topics/7053:

Errors in unpacking binary integers with high bit set:

<unpack b="8000000000000000">
   <signed>
      <int size="0">0</int>
      <int size="1">-128</int>
      <int size="2">-32768</int>
      <int size="3">-8388608</int>
      <int size="4">-1</int>
      <int size="5">-256</int>
      <int size="6">-65536</int>
      <int size="7">-16777216</int>
      <int size="8">-1</int>
   </signed>
   <unsigned>
      <int size="0">0</int>
      <int size="1">128</int>
      <int size="2">32768</int>
      <int size="3">8388608</int>
      <int size="4">2147483648</int>
      <int size="5">549755813888</int>
      <int size="6">140737488355328</int>
      <int size="7">36028797018963968</int>
      <int size="8">-9223372036854775808</int>
   </unsigned>
</unpack>

It turns out that internally an int constant, rather than a long is used during sign extension calculation, which accounts for the error at 32-bit negative. The issue at 64 bit results from the sign extension or problems of holding an unsigned long with the top bit set. This has been changed so that Big representations are used above 7 byte unpacks.

Note that one of the EXPath QT3 tests, EXPath-binary-unpack-unsigned-integer-012, which unpacks all 64 bits set, has an incorrect assertion of value == -1, whereas it should be 18446744073709551615