diff options
Diffstat (limited to 'src/Interpreter.ml')
| -rw-r--r-- | src/Interpreter.ml | 62 |
1 files changed, 27 insertions, 35 deletions
diff --git a/src/Interpreter.ml b/src/Interpreter.ml index a123f046..192dfe25 100644 --- a/src/Interpreter.ml +++ b/src/Interpreter.ml @@ -1267,38 +1267,34 @@ let give_back (config : C.config) (l : V.BorrowId.id) (bc : g_borrow_content) (** Convert an [avalue] to a [value]. This function is used when ending abstractions: whenever we end a borrow - in an abstraction, we converted the borrowed [avalue] to a [value], then give - back this [value] to the context. - - There are two possibilities: - - either the borrowed [avalue] contains ended regions, in which case we return ⊥ - - or it doesn't contain ⊥, in which case we simply return a newly introduced - symbolic value. - We return a new context because we may have to introduce a symbolic value. - - The `ended_regions` parameter is for the regions contained in the current - abstraction. + in an abstraction, we converted the borrowed [avalue] to a fresh symbolic + [value], then give back this [value] to the context. + + Note that some regions may have ended in the symbolic value we generate. + For instance, consider the following function signature: + ``` + fn f<'a>(x : &'a mut &'a mut u32); + ``` + When ending the abstraction, the value given back for the outer borrow + should be ⊥. In practice, we will give back a symbolic value which can't + be expanded (because expanding this symbolic value would require expanding + a reference whose region has already ended). *) -let convert_avalue_to_value (ended_regions : T.RegionId.set_t) - (av : V.typed_avalue) (ctx : C.eval_ctx) : C.eval_ctx * V.typed_value = +let convert_avalue_to_value (av : V.typed_avalue) (ctx : C.eval_ctx) : + C.eval_ctx * V.typed_value = (* Convert the type *) let ty = Subst.erase_regions av.V.ty in - (* Check if the avalue contains ended regions *) - if rty_regions_intersect av.V.ty ended_regions then - (* Contains ended regions: return ⊥ *) - (ctx, { V.value = V.Bottom; V.ty }) - else - (* Doesn't contain ended regions: return a symbolic value *) - let ctx, sv_id = C.fresh_symbolic_value_id ctx in - let svalue : V.symbolic_value = { V.sv_id; sv_ty = av.V.ty } in - let value : V.symbolic_proj_comp = - (* Note that the set of ended regions is empty: we shouldn't have to take - * into account any ended regions at this point, otherwise we would be in - * the first case where we should return ⊥ *) - { V.svalue; V.rset_ended = T.RegionId.Set.empty } - in - let value = V.Symbolic value in - (ctx, { V.value; V.ty }) + (* Generate the fresh a symbolic value *) + let ctx, sv_id = C.fresh_symbolic_value_id ctx in + let svalue : V.symbolic_value = { V.sv_id; sv_ty = av.V.ty } in + let value : V.symbolic_proj_comp = + (* Note that the set of ended regions is empty: we shouldn't have to take + * into account any ended regions at this point, otherwise we would be in + * the first case where we should return ⊥ *) + { V.svalue; V.rset_ended = T.RegionId.Set.empty } + in + let value = V.Symbolic value in + (ctx, { V.value; V.ty }) (** End a borrow identified by its borrow id in a context @@ -1564,12 +1560,8 @@ and end_abstraction_borrows (config : C.config) (abs_id : V.AbstractionId.id) let ctx = match bc with | V.AMutBorrow (bid, av) -> - (* First, convert the avalue to a value (by introducing the proper - * symbolic values). Note that we should probably use the regions owned - * by the abstraction for the ended_regions parameter, but for safety - * I'm using the accumulated regions (which include the ancestors' - * regions). Think a bit about that... *) - let ctx, v = convert_avalue_to_value abs.acc_regions av ctx in + (* First, convert the avalue to a (fresh symbolic) value *) + let ctx, v = convert_avalue_to_value av ctx in give_back_value config bid v ctx | V.ASharedBorrow bid -> give_back_shared config bid ctx | V.AProjSharedBorrow _ -> |