Spurious loss of deterministic behavior after generating some amount of Bits32s about idris-tf-random HOT 5 CLOSED

I found something that might be involved
https://github.com/idris-lang/Idris-dev/blob/master/rts/idris_bitstring.c
on line 585 the zero-extending conversion from B8 to B64 gives the VAL the wrong type code, BITS16.
Because the value in the info union is still right, this explains why the bug went unnoticed. I am looking for ways to use this to cause an incorrect result with a program, but tf-random may have already done this.

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Probably the wrong place for this, but just to follow up, having bits64 copied into a bits16 value may have the effect of a gc operation moving only part of the info union, losing information at an unpredictable time in the future.

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idris-lang/Idris-dev#1599

Though after making this change locally and rebuilding everything, it turns out my test program does not use the broken function at all. So the bug is still happening. The search continues.

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http://lpaste.net/112176

This is my first attempt to use printf's to check the running program.

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Thank you very much for working this out!

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