Here are the known bugs in MLton 20051202, listed in reverse chronological order of date reported.

Bug in the Real<N>.fmt, Real<N>.fromString, Real<N>.scan, and Real<N>.toString functions of the Basis Library implementation. These functions were using TO_NEAREST semantics, but should obey the current rounding mode. (Only Real<N>.fmt StringCvt.EXACT, Real<N>.fromDecimal, and Real<N>.toDecimal are specified to override the current rounding mode with TO_NEAREST semantics.)
Thanks to Sean McLaughlin for the bug report.
Fixed by revision r5827.

Bug in the treatment of floatingpoint operations. Floatingpoint operations depend on the current rounding mode, but were being treated as pure.
Thanks to Sean McLaughlin for the bug report.
Fixed by revision r5794.

Bug in the Real32.toInt function of the Basis Library implementation could lead incorrect results when applied to a Real32.real value numerically close to valOf(Int.maxInt).
Fixed by revision r5764.

The Socket structure of the Basis Library implementation used andb rather than orb to unmarshal socket options (for Socket.Ctl.get<OPT> functions).
Thanks to Anders Petersson for the bug report and patch.
Fixed by revision r5735.

Bug in the Date structure of the Basis Library implementation yielded some functions that would erroneously raise Date when applied to a year before 1900.
Thanks to Joe Hurd for the bug report.
Fixed by revision r5732.

Bug in monomorphisation pass could exhibit the error Type error: type mismatch.
Thanks to Vesa Karvonen for the bug report.
Fixed by revision r5731.

The PackReal<N>.toBytes function in the Basis Library implementation incorrectly shared (and mutated) the result vector.
Thanks to Eric McCorkle for the bug report and patch.
Fixed by revision r5281.

Bug in elaboration of FFI forms. Using a unary FFI types (e.g., array, ref, vector) in places where MLton.Pointer.t was required would lead to an internal error TypeError.
Fixed by revision r4890.

The MONO_VECTOR signature of the Basis Library implementation incorrectly omits the specification of find.
Fixed by revision r4707.

The optimizer reports an internal error (TypeError) when an imported C function is called but not used.
Thanks to "jq" for the bug report.
Fixed by revision r4690.

Bug in pass to flatten data structures.
Thanks to Joe Hurd for the bug report.
Fixed by revision r4662.

The native codegen’s implementation of the Ccalling convention failed to widen 16bit arguments to 32bits.
Fixed by revision r4631.

The PACK_REAL structures of the Basis Library implementation used byte, rather than element, indexing.
Fixed by revision r4411.

MLton.share could cause a segmentation fault.
Fixed by revision r4400.

The SSA simplifier could eliminate an irredundant test.
Fixed by revision r4370.

A program with a very large number of functors could exhibit the error ElaborateEnv.functorClosure: firstTycons.
Fixed by revision r4344.