diff options
Diffstat (limited to 'cparser/Ceval.ml')
| -rw-r--r-- | cparser/Ceval.ml | 92 |
1 files changed, 91 insertions, 1 deletions
diff --git a/cparser/Ceval.ml b/cparser/Ceval.ml index c3d7eeeb..f479ad5c 100644 --- a/cparser/Ceval.ml +++ b/cparser/Ceval.ml @@ -13,7 +13,7 @@ (* *) (* *********************************************************************) -(* Evaluation of compile-time constants *) +(* Evaluation and recognition of compile-time constants *) open C open Cutil @@ -279,3 +279,93 @@ let constant_expr env ty e = | TEnum(_, _), I n -> Some(CInt(n, enum_ikind, "")) | _ -> None with Notconst -> None + +(* Recognition of constant initializers and constant expressions. + This is just a check: no evaluation of the constants is done. + Reference: ISO C99 section 6.6 *) + +let rec is_constant_init env = function + | Init_single e -> is_constant_expr env e + | Init_array il -> List.for_all (is_constant_init env) il + | Init_struct(id, fil) -> + List.for_all (fun (f, i) -> is_constant_init env i) fil + | Init_union(id, f, i) -> is_constant_init env i + +and is_constant_expr env e = + match e.edesc with + | EConst cst -> true + | ESizeof ty -> true + | EAlignof ty -> true + | EVar id -> + begin match Env.find_ident env id with + | Env.II_ident _ -> is_constant_rval_of_lval env e + | Env.II_enum _ -> true (* an enum value is a constant *) + | exception Env.Error _ -> false (* should not happen *) + end + | EUnop(op, e1) -> + begin match op with + | Ominus | Oplus | Olognot | Onot -> is_constant_expr env e1 + | Oderef | Odot _ | Oarrow _ -> is_constant_rval_of_lval env e + | Oaddrof -> is_constant_lval env e1 + | Opreincr | Opredecr | Opostincr | Opostdecr -> false + (* Constant expressions shall not contain increment or decrement *) + end + | EBinop(op, e1, e2, _) -> + begin match op with + | Oadd | Osub | Omul | Odiv | Omod + | Oand | Oor | Oxor | Oshl | Oshr + | Oeq | One | Olt | Ogt | Ole | Oge + | Ocomma | Ologand | Ologor -> + is_constant_expr env e1 && is_constant_expr env e2 + (* ISO C99 says that constant expressions shall not contain comma + operators. However, clang accepts them, and they are harmless. *) + | Oindex -> + is_constant_rval_of_lval env e + | Oassign + | Oadd_assign | Osub_assign | Omul_assign | Odiv_assign | Omod_assign + | Oand_assign | Oor_assign | Oxor_assign | Oshl_assign | Oshr_assign -> + false + (* constant expressions shall not contain assignments *) + end + | EConditional(e1, e2, e3) -> + is_constant_expr env e1 && is_constant_expr env e2 + && is_constant_expr env e3 + | ECast(ty, e1) -> + is_constant_expr env e1 + | ECompound(ty, i) -> + is_constant_init env i + | ECall(fn, args) -> + false + (* constant expressions shall not contain function calls *) + +and is_constant_rval_of_lval env e = + (* The value of an object shall not be accessed by use of the . -> * [] + operators. This is the case if the object has array or function type. + A scalar type or a composite type implies a memory access. *) + match unroll env e.etyp with + | TArray _ | TFun _ -> is_constant_lval env e + | _ -> false + +and is_constant_lval env e = + match e.edesc with + | EVar id -> + begin match Env.find_ident env id with + | Env.II_ident(sto, _) -> + begin match sto with + | Storage_default | Storage_extern | Storage_static -> true + | Storage_auto | Storage_register -> false + end + | Env.II_enum _ -> false (* should not happen *) + | exception Env.Error _ -> false (* should not happen *) + end + | EUnop(Oderef, e1) -> is_constant_expr env e1 + | EUnop(Odot f, e1) -> is_constant_lval env e1 + | EUnop(Oarrow f, e1) -> is_constant_expr env e1 + | EBinop(Oindex, e1, e2, _) -> + is_constant_expr env e1 && is_constant_expr env e2 + | ECompound(ty, i) -> + is_constant_init env i + | _ -> false + + + |