package frama-c

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Validity
Finding bases
Origin of the variable underlying a base
NULL base
Size of a base
Misc
Registering bases
Substituting bases

Platform dedicated to the analysis of source code written in C

Install

dune-project

Dependency

frama-c.com Readme Edit opam file Versions (25)

Authors

Maintainers

F

frama-ci-bot@frama-c.com

Sources

frama-c-29.0-Copper.tar.gz

sha256=d2fbb3b8d0ff83945872e9e6fa258e934a706360e698dae3b4d5f971addf7493

doc/frama-c.kernel/Frama_c_kernel/Base/index.html

Module `Frama_c_kernel.Base`

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

type cstring =

| CSString of string
| 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 {

mutable weak : bool;
(*
Indicate that the variable is weak, i.e. that it may represent multiple memory locations
*)
mutable min_alloc : Abstract_interp.Int.t;
(*
First bit guaranteed to be valid; can be -1
*)
mutable max_alloc : Abstract_interp.Int.t;
(*
Last possibly valid bit
*)
max_allocable : Abstract_interp.Int.t;
(*
Maximum valid bit after size increase
*)

}

Validity for variables that might change size.

type deallocation =

| Malloc
| VLA
| 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

| Var of Cil_types.varinfo * validity
(*
Base for a standard C variable.
*)
| CLogic_Var of Cil_types.logic_var * Cil_types.typ * validity
(*
Base for a logic variable that has a C type.
*)
| Null
(*
Base for an address like (int* )0x123
*)
| String of int * cstring
(*
String(id, s)
- id: unique id of the constant string (one per code location)
- s: contents of the constant string
*)
| Allocated of Cil_types.varinfo * deallocation * validity
(*
Base for a variable dynamically allocated via malloc/calloc/realloc/alloca
*)

and validity =

| Empty
(*
For 0-sized bases
*)
| Known of Abstract_interp.Int.t * Abstract_interp.Int.t
(*
Valid between those two bits
*)
| 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.
*)
| 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.
*)
| 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

include Datatype.Ty with type t = base

type t = base

see https://frama-c.com/download/frama-c-plugin-development-guide.pdf

val ty : t Type.t

see https://frama-c.com/download/frama-c-plugin-development-guide.pdf

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

Equality: same spec than Stdlib.(=).

see https://frama-c.com/download/frama-c-plugin-development-guide.pdf

val compare : t -> t -> int

Comparison: same spec than Stdlib.compare.

val hash : t -> int

Hash function: same spec than Hashtbl.hash.

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

Pretty print each value in an user-friendly way.

see https://frama-c.com/download/frama-c-plugin-development-guide.pdf

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 Hptshape.map

module SetLattice : Lattice_type.Lattice_Set with module O = Hptset

module Validity : Datatype.S with type t = validity

val pretty_addr : 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.

Validity

val pretty_validity : 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 =

| Invalid_range
| Valid_range of Int_Intervals_sig.itv 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).

raises Not_a_C_variable
otherwise.

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 =

| Read of Abstract_interp.Int.t
| Write of Abstract_interp.Int.t
| 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).

Misc

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 Hptshape.map

Type used for the substitution between bases.

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

Creates a substitution from an association list.