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Fix potential overflow bug. #227

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May 6, 2016
Merged

Fix potential overflow bug. #227

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9 changes: 6 additions & 3 deletions src/dfa.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,9 +66,12 @@ use sparse::SparseSet;
pub fn can_exec(insts: &Program) -> bool {
use prog::Inst::*;
// If for some reason we manage to allocate a regex program with more
// than u32::MAX instructions, then we can't execute the DFA because we
// use 32 bit instruction pointers for memory savings.
if insts.len() > ::std::u32::MAX as usize {
// than i32::MAX instructions, then we can't execute the DFA because we
// use 32 bit instruction pointer deltas for memory savings.
// If i32::MAX is the largest positive delta,
// then -i32::MAX == i32::MIN + 1 is the largest negative delta,
// and we are OK to use 32 bits.
if insts.len() > ::std::i32::MAX as usize {
return false;
}
for inst in insts {
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