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rustc: check for signed division/remainder overflow.

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This commit is contained in:
Eduard Burtescu 2015-01-29 13:43:55 +02:00
parent cb3c9a1e88
commit bd9c67e181
1 changed files with 35 additions and 7 deletions
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42
src/librustc/middle/const_eval.rs
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@ -27,6 +27,7 @@ use syntax::{ast_map, ast_util, codemap};
use std::cmp::Ordering;
use std::collections::hash_map::Entry::Vacant;
use std::{i8, i16, i32, i64};
use std::rc::Rc;
fn lookup_const<'a>(tcx: &'a ty::ctxt, e: &Expr) -> Option<&'a Expr> {
@ -263,19 +264,46 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
}
}
(Ok(const_int(a)), Ok(const_int(b))) => {
let is_a_min_value = |&:| {
let int_ty = match ty::expr_ty_opt(tcx, e).map(|ty| &ty.sty) {
Some(&ty::ty_int(int_ty)) => int_ty,
_ => return false
};
let int_ty = if let ast::TyIs(_) = int_ty {
tcx.sess.target.int_type
} else {
int_ty
};
match int_ty {
ast::TyI8 => (a as i8) == i8::MIN,
ast::TyI16 => (a as i16) == i16::MIN,
ast::TyI32 => (a as i32) == i32::MIN,
ast::TyI64 => (a as i64) == i64::MIN,
ast::TyIs(_) => unreachable!()
}
};
match op.node {
ast::BiAdd => Ok(const_int(a + b)),
ast::BiSub => Ok(const_int(a - b)),
ast::BiMul => Ok(const_int(a * b)),
ast::BiDiv if b == 0 => {
Err("attempted to divide by zero".to_string())
ast::BiDiv => {
if b == 0 {
Err("attempted to divide by zero".to_string())
} else if b == -1 && is_a_min_value() {
Err("attempted to divide with overflow".to_string())
} else {
Ok(const_int(a / b))
}
}
ast::BiDiv => Ok(const_int(a / b)),
ast::BiRem if b == 0 => {
Err("attempted remainder with a divisor of \
zero".to_string())
ast::BiRem => {
if b == 0 {
Err("attempted remainder with a divisor of zero".to_string())
} else if b == -1 && is_a_min_value() {
Err("attempted remainder with overflow".to_string())
} else {
Ok(const_int(a % b))
}
}
ast::BiRem => Ok(const_int(a % b)),
ast::BiAnd | ast::BiBitAnd => Ok(const_int(a & b)),
ast::BiOr | ast::BiBitOr => Ok(const_int(a | b)),
ast::BiBitXor => Ok(const_int(a ^ b)),