From 50d11b90caf6545556fc090858c694e19f3c7683 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Tue, 12 May 2009 11:06:24 +0000 Subject: * Allow unsafe (unspecified) comparisons between attrsets unless NIX_NO_UNSAFE_EQ is set, for now. --- src/libexpr/eval.cc | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'src/libexpr/eval.cc') diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 2b9b96559d7d..cd9c64594747 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) { -- cgit 1.4.1