Strange test failure when running with valgrind

[John W. Eaton]

The following test, and a similar one with int64 instead of uint64, 
fails when running Octave with valgrind:

  a = 1.9*2^61; b = uint64 (a); b++; assert (b > a);

The test does not fail when Octave is running normally (without valgrind).

Any ideas about why could that be?

When the test fails, it appears that b == a, though b++ does appear to 
increment the initial value of b, and b appears to be the same value in 
both cases (with and without valgrind).

jwe