diff options
| -rw-r--r-- | src/libexpr/eval.cc | 8 | ||||
| -rw-r--r-- | src/libexpr/eval.hh | 2 |
2 files changed, 9 insertions, 1 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 2b9b96559..cd9c64594 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -23,6 +23,8 @@ EvalState::EvalState() initNixExprHelpers(); addPrimOps(); + + allowUnsafeEquality = getEnv("NIX_NO_UNSAFE_EQ", "") == ""; } @@ -661,9 +663,13 @@ LocalNoInline(bool areEqual(EvalState & state, Expr e1, Expr e2)) /* Functions are incomparable. */ if (sym1 == symFunction || sym1 == symPrimOp) return false; - if (sym1 == symAttrs) + if (!state.allowUnsafeEquality && sym1 == symAttrs) throw EvalError("comparison of attribute sets is not implemented"); + /* !!! This allows comparisons of infinite data structures to + succeed, such as `let x = [x]; in x == x'. This is + undesirable, since equivalent (?) terms such as `let x = [x]; y + = [y]; in x == y' don't terminate. */ if (e1 == e2) return true; if (sym1 == symList) { diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh index 5699d455c..fed6d3472 100644 --- a/src/libexpr/eval.hh +++ b/src/libexpr/eval.hh @@ -38,6 +38,8 @@ struct EvalState unsigned int nrEvaluated; unsigned int nrCached; + bool allowUnsafeEquality; + EvalState(); void addPrimOps(); |