Fix integer overflow in >>/2 and <</2
This commit is contained in:
Emilie Burgun
@@ -629,103 +629,110 @@ pub(crate) fn int_floor_div(
|
||||
idiv(n1, n2, arena)
|
||||
}
|
||||
|
||||
pub(crate) fn shr(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, MachineStubGen> {
|
||||
pub(crate) fn shr(lhs: Number, rhs: Number, arena: &mut Arena) -> Result<Number, MachineStubGen> {
|
||||
let stub_gen = || {
|
||||
let shr_atom = atom!(">>");
|
||||
functor_stub(shr_atom, 2)
|
||||
};
|
||||
|
||||
if n2.is_integer() && n2.is_negative() {
|
||||
return shl(n1, neg(n2, arena), arena);
|
||||
if rhs.is_integer() && rhs.is_negative() {
|
||||
return shl(lhs, neg(rhs, arena), arena);
|
||||
}
|
||||
|
||||
match (n1, n2) {
|
||||
(Number::Fixnum(n1), Number::Fixnum(n2)) => {
|
||||
let n1_i = n1.get_num();
|
||||
let n2_i = n2.get_num();
|
||||
match lhs {
|
||||
Number::Fixnum(lhs) => {
|
||||
let rhs = match rhs {
|
||||
Number::Fixnum(fix) => fix.get_num().try_into().unwrap_or(u32::MAX),
|
||||
Number::Integer(int) => (&*int).try_into().unwrap_or(u32::MAX),
|
||||
other => {
|
||||
return Err(numerical_type_error(ValidType::Integer, other, stub_gen));
|
||||
}
|
||||
};
|
||||
|
||||
// FIXME(arithmetic_overflow)
|
||||
// what should this do for too large n2,
|
||||
// - logical right shift should probably turn to 0
|
||||
// - arithmetic right shift should maybe differ for negative numbers
|
||||
//
|
||||
// note: negaitve n2 is already handled above
|
||||
#[allow(arithmetic_overflow)]
|
||||
if let Ok(n2) = usize::try_from(n2_i) {
|
||||
Ok(Number::arena_from(n1_i >> n2, arena))
|
||||
} else {
|
||||
Ok(Number::arena_from(n1_i >> usize::MAX, arena))
|
||||
}
|
||||
let res = lhs.get_num().checked_shr(rhs).unwrap_or(0);
|
||||
Ok(Number::arena_from(res, arena))
|
||||
}
|
||||
(Number::Fixnum(n1), Number::Integer(n2)) => {
|
||||
let n1 = Integer::from(n1.get_num());
|
||||
Number::Integer(lhs) => {
|
||||
// Note: bigints require `log(n)` bits of space. If `rhs > usize::MAX`,
|
||||
// then this clamping only becomes an issue when `lhs < 2 ^ (usize::MAX)`:
|
||||
// - on 32-bit systems, `lhs` would need to be 512MiB big (1/8th of the addressable memory)
|
||||
// - on 64-bit systems, `lhs` would need to be 2EiB big (!!!)
|
||||
let rhs = match rhs {
|
||||
Number::Fixnum(fix) => fix.get_num().try_into().unwrap_or(usize::MAX),
|
||||
Number::Integer(int) => (&*int).try_into().unwrap_or(usize::MAX),
|
||||
other => {
|
||||
return Err(numerical_type_error(ValidType::Integer, other, stub_gen));
|
||||
}
|
||||
};
|
||||
|
||||
let result: Result<usize, _> = (&*n2).try_into();
|
||||
|
||||
match result {
|
||||
Ok(n2) => Ok(Number::arena_from(n1 >> n2, arena)),
|
||||
Err(_) => Ok(Number::arena_from(n1 >> usize::MAX, arena)),
|
||||
}
|
||||
Ok(Number::arena_from(Integer::from(&*lhs >> rhs), arena))
|
||||
}
|
||||
(Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
|
||||
Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena)),
|
||||
_ => Ok(Number::arena_from(Integer::from(&*n1 >> usize::MAX), arena)),
|
||||
},
|
||||
(Number::Integer(n1), Number::Integer(n2)) => {
|
||||
let result: Result<usize, _> = (&*n2).try_into();
|
||||
|
||||
match result {
|
||||
Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena)),
|
||||
Err(_) => Ok(Number::arena_from(Integer::from(&*n1 >> usize::MAX), arena)),
|
||||
}
|
||||
}
|
||||
(Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
|
||||
(Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
|
||||
(n1, _) => Err(numerical_type_error(ValidType::Integer, n1, stub_gen)),
|
||||
other => Err(numerical_type_error(ValidType::Integer, other, stub_gen)),
|
||||
}
|
||||
}
|
||||
|
||||
pub(crate) fn shl(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, MachineStubGen> {
|
||||
pub(crate) fn shl(lhs: Number, rhs: Number, arena: &mut Arena) -> Result<Number, MachineStubGen> {
|
||||
let stub_gen = || {
|
||||
let shl_atom = atom!("<<");
|
||||
functor_stub(shl_atom, 2)
|
||||
};
|
||||
|
||||
if n2.is_integer() && n2.is_negative() {
|
||||
return shr(n1, neg(n2, arena), arena);
|
||||
if rhs.is_integer() && rhs.is_negative() {
|
||||
return shr(lhs, neg(rhs, arena), arena);
|
||||
}
|
||||
|
||||
match (n1, n2) {
|
||||
(Number::Fixnum(n1), Number::Fixnum(n2)) => {
|
||||
let n1_i = n1.get_num();
|
||||
let n2_i = n2.get_num();
|
||||
let rhs = match rhs {
|
||||
Number::Fixnum(fix) => fix.get_num().try_into().unwrap_or(usize::MAX),
|
||||
Number::Integer(int) => (&*int).try_into().unwrap_or(usize::MAX),
|
||||
other => {
|
||||
return Err(numerical_type_error(ValidType::Integer, other, stub_gen));
|
||||
}
|
||||
};
|
||||
|
||||
if let Ok(n2) = usize::try_from(n2_i) {
|
||||
Ok(Number::arena_from(n1_i << n2, arena))
|
||||
match lhs {
|
||||
Number::Fixnum(lhs) => {
|
||||
let lhs = lhs.get_num();
|
||||
|
||||
if let Some(res) = checked_signed_shl(lhs, rhs) {
|
||||
Ok(Number::arena_from(res, arena))
|
||||
} else {
|
||||
let n1 = Integer::from(n1_i);
|
||||
Ok(Number::arena_from(n1 << usize::MAX, arena))
|
||||
let lhs = Integer::from(lhs);
|
||||
Ok(Number::arena_from(
|
||||
Integer::from(lhs << (rhs as usize)),
|
||||
arena,
|
||||
))
|
||||
}
|
||||
}
|
||||
(Number::Fixnum(n1), Number::Integer(n2)) => {
|
||||
let n1 = Integer::from(n1.get_num());
|
||||
Number::Integer(lhs) => Ok(Number::arena_from(
|
||||
Integer::from(&*lhs << (rhs as usize)),
|
||||
arena,
|
||||
)),
|
||||
other => Err(numerical_type_error(ValidType::Integer, other, stub_gen)),
|
||||
}
|
||||
}
|
||||
|
||||
match (&*n2).try_into() as Result<usize, _> {
|
||||
Ok(n2) => Ok(Number::arena_from(n1 << n2, arena)),
|
||||
_ => Ok(Number::arena_from(n1 << usize::MAX, arena)),
|
||||
}
|
||||
/// Returns `x << shift`, checking for overflow and for values of `shift` that are too big.
|
||||
#[inline]
|
||||
fn checked_signed_shl(x: i64, shift: usize) -> Option<i64> {
|
||||
if shift == 0 {
|
||||
return Some(x);
|
||||
}
|
||||
|
||||
if x >= 0 {
|
||||
// Note: for unsigned integers, the condition would usually be spelled
|
||||
// `shift <= x.leading_zeros()`, but since the MSB for signed integers
|
||||
// controls the sign, we need to make sure that `shift` is at most
|
||||
// `x.leading_zeros() - 1`.
|
||||
if shift < x.leading_zeros() as usize {
|
||||
Some(x << shift)
|
||||
} else {
|
||||
None
|
||||
}
|
||||
(Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
|
||||
Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 << n2), arena)),
|
||||
_ => Ok(Number::arena_from(Integer::from(&*n1 << usize::MAX), arena)),
|
||||
},
|
||||
(Number::Integer(n1), Number::Integer(n2)) => match (&*n2).try_into() as Result<usize, _> {
|
||||
Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 << n2), arena)),
|
||||
_ => Ok(Number::arena_from(Integer::from(&*n1 << usize::MAX), arena)),
|
||||
},
|
||||
(Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
|
||||
(Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
|
||||
(n1, _) => Err(numerical_type_error(ValidType::Integer, n1, stub_gen)),
|
||||
} else {
|
||||
let y = x.checked_neg()?;
|
||||
// FIXME: incorrectly rejects `-2 ^ 62 << 1`. This is currently a non-issue,
|
||||
// since the bitshift is then done as a `Number::Integer`
|
||||
checked_signed_shl(y, shift).and_then(|res| res.checked_neg())
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
Reference in New Issue
Block a user