I'm not sure this is a bug, but I was advised to post here.
Some tests fails in x64 Interix, see shell output in attached file. There is one tests which core dumps, a few fails due to missing encodings and some tests fails integer conversion.
I think the integer conversion failures are the most important at first.
Note that type long is 64bit in my system.
$ uname -a
Interix max2008 6.0 10.0.6030.0 genuineintel Intel64_Family_15_Model_6_Stepping_5
Which means NT POSIX subsystem (SUA) with Interix SDK 6.0 on a x64 Windows 2008 machine.
This system has LP64 (long type is 64bit)
GNU make, GNU m4, Interix Korn shell and cc script as compiler (wraps MS x64 Compiler 15.00.21022.08).