ANSI/ISO C Specification Language
|Paradigm||declarative with few imperative features.|
|Designed by||Commissariat à l'Énergie Atomique and INRIA|
|Developer||Commissariat à l'Énergie Atomique and INRIA|
|2008 / December 2008|
The ANSI/ISO C Specification Language (ACSL) is a specification language for C programs, using Hoare style pre- and postconditions and invariants, that follows the design by contract paradigm. Specifications are written as C annotation comments to the C program, which hence can be compiled with any C compiler.
The current verification tool for ACSL is Frama-C.
In 1983, the American National Standards Institute (ANSI) commissioned a committee, X3J11, to standardize the C language. The first standard for C was published by ANSI. Although this document was subsequently adopted by International Organization for Standardization (ISO) and subsequent revisions published by ISO have been adopted by ANSI, the name ANSI C continues to be used.
ACSL is a Behavioral Interface Specification Language (BISL). It aims at specifying behavioral properties of C source code. The main inspiration for this language comes from the specification language of the Caduceus tool for deductive verification of behavioral properties of C programs. The specification language of Caduceus is itself inspired from JML which aims at similar goals for Java source code.
One difference with JML, is that ACSL aims at static verification and deductive verification whereas JML aims both at runtime assertion checking and static verification using for instance the ESC/Java tool.
Let us consider the following example for the prototype of a function named
/*@ requires \valid(p);
@ assigns *p;
@ ensures *p == \old(*p) + 1;
void incrstar (int *p);
The contract is given by the comment which starts with
/*@. Its meaning is as follows:
- the first line is a precondition: it states that function
incrstarmust be called with a pointer
pthat points to a safely allocated memory location.
- Second line is a frame clause, stating that function
incrstardoes not modify any memory location but the one pointed to by
- Finally, the
ensuresclause is a postcondition, which specifies that the value
*pis incremented by one.
Most of the features of ACSL are supported by Frama-C.
- Example of ACSL usage Sufficient Preconditions for Modular Assertion Checking in VMCAI 2008 pages 188-202.
- Fraunhofer FOKUS maintains ACSL By Example, a collection of ACSL specification for simple algorithms in C 
- Report mentioning the use of ACSL in teaching , Петренко Ольга Леонидовна and Хорошилов Алексей Владимирович.
- At Technikum Wien ACSL and Frama-C are taught in a course on design and verification.