diff options
| -rw-r--r-- | src/librustc/middle/const_eval.rs | 42 |
1 files changed, 35 insertions, 7 deletions
diff --git a/src/librustc/middle/const_eval.rs b/src/librustc/middle/const_eval.rs index 72600347334..3d03cd946c4 100644 --- a/src/librustc/middle/const_eval.rs +++ b/src/librustc/middle/const_eval.rs @@ -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)), |