Mark Dickinson <[email protected]> added the comment:
Thanks for the details. So the relevant code (see the float_hex function in
Objects/floatobject.c) looks like this:
if (x == 0.0) {
if(copysign(1.0, x) == -1.0)
return PyString_FromString("-0x0.0p+0");
else
return PyString_FromString("0x0.0p+0");
}
This *should* produce the correct string for -0.0 (because -0.0 compares equal
to 0.0, and then copysign(1.0, x) should be -1.0); I'm reasonably confident
that the C code is correct, since the tests pass on all the other platforms
that get tested regularly.
So a buggy system copysign function looks like a possibility. Another more
likely possibility occurs to me, though: and that's that there's a buggy
compiler optimization going on: the compiler sees that we're in an 'x == 0.0'
branch, and decides that it can substitute '0.0' for 'x' everywhere in the 'if'
block. But this is just guessing.
Do you still get these failures in a debug build of Python (i.e., by passing
--with-pydebug to the configure script)?
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