Frama-C API - Base

Abstraction of the base of an addressable memory zone, together with the validity of the zone.

type cstring =
  1. | CSString of string
  2. | CSWstring of Escape.wstring

    This type abstracts over the two kinds of constant strings present in strings. It is used in a few modules below Base.

type variable_validity = private {
  1. mutable weak : bool;

    Indicate that the variable is weak, i.e. that it may represent multiple memory locations

  2. mutable min_alloc : Abstract_interp.Int.t;

    First bit guaranteed to be valid; can be -1

  3. mutable max_alloc : Abstract_interp.Int.t;

    Last possibly valid bit

  4. max_allocable : Abstract_interp.Int.t;

    Maximum valid bit after size increase


Validity for variables that might change size.

type deallocation =
  1. | Malloc
  2. | VLA
  3. | Alloca

Whether the allocated base has been obtained via calls to malloc/calloc/realloc (Malloc), alloca (Alloca), or is related to a variable-length array (VLA).

type base = private
  1. | Var of Cil_types.varinfo * validity

    Base for a standard C variable.

  2. | CLogic_Var of Cil_types.logic_var * Cil_types.typ * validity

    Base for a logic variable that has a C type.

  3. | Null

    Base for an address like (int* )0x123

  4. | String of int * cstring

    String(id, s)

    • id: unique id of the constant string (one per code location)
    • s: contents of the constant string
  5. | Allocated of Cil_types.varinfo * deallocation * validity

    Base for a variable dynamically allocated via malloc/calloc/realloc/alloca

and validity =
  1. | Empty

    For 0-sized bases

  2. | Known of Abstract_interp.Int.t * Abstract_interp.Int.t

    Valid between those two bits

  3. | Unknown of Abstract_interp.Int.t * Abstract_interp.Int.t option * Abstract_interp.Int.t

    Unknown(b,k,e) indicates: If k is None, potentially valid between b and e If k is Some k, then b <= k <= e, and the base is

    • valid between b and k;
    • potentially valid between k+1 and e: Accesses on potentially valid parts will succeed, but will also raise an alarm.
  4. | Variable of variable_validity

    Variable(min_alloc, max_alloc) means:

    • all offsets between 0 and min_alloc are valid; min_alloc can be -1, in which case no offsets are guaranteed to be valid.
    • offsets between min_alloc+1 and max_alloc are potentially valid;
    • offsets above max_alloc+1 are invalid.
  5. | Invalid

    Valid nowhere. Typically used for the NULL base, or for function pointers.

module Base : sig ... end
include Datatype.S_with_collections with type t = base
include Datatype.S with type t = base
include Datatype.S_no_copy with type t = base
val name : string

Unique name of the datatype.

val descr : t Descr.t

Datatype descriptor.

val packed_descr : Structural_descr.pack

Packed version of the descriptor.

val reprs : t list

List of representants of the descriptor.

val equal : t -> t -> bool
val compare : t -> t -> int

Comparison: same spec than

val hash : t -> int

Hash function: same spec than Hashtbl.hash.

val pretty : Stdlib.Format.formatter -> t -> unit

Pretty print each value in an user-friendly way.

val mem_project : (Project_skeleton.t -> bool) -> t -> bool

mem_project f x must return true iff there is a value p of type Project.t in x such that f p returns true.

val copy : t -> t

Deep copy: no possible sharing between x and copy x.

module Set : Datatype.Set with type elt = t
module Map : Datatype.Map with type key = t
module Hashtbl : Datatype.Hashtbl with type key = t
module Hptshape : Hptmap_sig.Shape with type key = t and type 'v map = 'v Hptmap.Shape(Base).t
module Hptset : Hptset.S with type elt = t and type 'v map = 'v
module Validity : Datatype.S with type t = validity
val pretty_addr : Stdlib.Format.formatter -> t -> unit

pretty_addr fmt base pretty-prints the name of base on fmt, with a leading ampersand if it is a variable

val typeof : t -> Cil_types.typ option

Type of the memory block that starts from the given base. Useful to give to the function Bit_utils.pretty_bits, typically.


val pretty_validity : Stdlib.Format.formatter -> validity -> unit
val validity : t -> validity
val validity_from_size : Abstract_interp.Int.t -> validity

validity_from_size size returns Empty if size is zero, or Known (0, size-1) if size > 0. size must not be negative.

  • since Aluminium-20160501
val validity_from_type : Cil_types.varinfo -> validity
type range_validity =
  1. | Invalid_range
  2. | Valid_range of option
val valid_range : validity -> range_validity

valid_range v returns Invalid_range if v is Invalid, Valid_range None if v is Empty, or Valid_range (Some (mn, mx)) otherwise, where mn and mx are the minimum and maximum (possibly) valid bounds of v.

val is_weak_validity : validity -> bool

is_weak_validity v returns true iff v is a Weak validity.

val create_variable_validity : weak:bool -> min_alloc:Abstract_interp.Int.t -> max_alloc:Abstract_interp.Int.t -> variable_validity
val update_variable_validity : variable_validity -> weak:bool -> min_alloc:Abstract_interp.Int.t -> max_alloc:Abstract_interp.Int.t -> unit

Update the corresponding fields of the variable validity. Bases already weak cannot be made 'strong' through this function, and the validity bounds can only grow.

Finding bases

val of_varinfo : Cil_types.varinfo -> t
val of_string_exp : Cil_types.exp -> t
val of_c_logic_var : Cil_types.logic_var -> t

Must only be called on logic variables that have a C type

Origin of the variable underlying a base

exception Not_a_C_variable
val to_varinfo : t -> Cil_types.varinfo
  • returns

    the variable's varinfo if the base corresponds to a C variable (in particular, not a logic variable).

val is_formal_or_local : t -> Cil_types.fundec -> bool
val is_any_formal_or_local : t -> bool
val is_any_local : t -> bool
val is_global : t -> bool
val is_formal_of_prototype : t -> Cil_types.varinfo -> bool
val is_local : t -> Cil_types.fundec -> bool
val is_formal : t -> Cil_types.fundec -> bool
val is_block_local : t -> Cil_types.block -> bool
val is_function : t -> bool

NULL base

val null : t
val is_null : t -> bool
val null_set : Hptset.t

Set containing only the base null.

val min_valid_absolute_address : unit -> Abstract_interp.Int.t
val max_valid_absolute_address : unit -> Abstract_interp.Int.t

Bounds for option absolute-valid-range

Size of a base

val bits_sizeof : t -> Int_Base.t
type access =
  1. | Read of Abstract_interp.Int.t
  2. | Write of Abstract_interp.Int.t
  3. | No_access

Access kind: read/write of k bits, or no access. Without any access, an offset must point into or just beyond the base ("one past the last element of the array object", non-array object being viewed as array of one element).

val is_valid_offset : access -> t -> Ival.t -> bool

is_valid_offset access b offset holds iff the ival offset (expressed in bits) is completely valid for the access of base b (it only represents valid offsets for such an access). Returns false if offset may be invalid for such an access.

val valid_offset : ?bitfield:bool -> access -> t -> Ival.t

Computes all offsets that may be valid for an access of base t. For bases with variable or unknown validity, the result may not satisfy is_valid_offset, as some offsets may be valid or invalid. bitfield is true by default: the computed offset may be offsets of bitfields. If it is set to false, the computed offsets are byte aligned (they are all congruent to 0 modulo 8).


val is_read_only : t -> bool

Is the base valid as a read/write location, or only for reading. The const attribute is not currently taken into account.

val is_weak : t -> bool

Is the given base a weak one (in the sens that its validity is Weak). Only possible for Allocated bases.

val id : t -> int
val is_aligned_by : t -> Abstract_interp.Int.t -> bool

Registering bases

This is only useful to create an initial memory state for analysis, and is never needed for normal users.

val register_allocated_var : Cil_types.varinfo -> deallocation -> validity -> t

Allocated variables are variables not present in the source of the program, but instead created through dynamic allocation. Their field vsource is set to false.

val register_memory_var : Cil_types.varinfo -> validity -> t

Memory variables are variables not present in the source of the program. They are created only to fill the contents of another variable. Their field vsource is set to false.

Substituting bases

This is used to efficiently replace some bases by others in locations or in memory states, for instance in Locations or Lmap_sig.

type substitution = base

Type used for the substitution between bases.

val substitution_from_list : (base * base) list -> substitution

Creates a substitution from an association list.