Synthetic Separation Logic

Synthesis of Heap-Manipulating Programs from Separation Logic Specifications

Theory Behind the Tool

The details of Synthetic Separation Logic cand be found in the accompanying draft paper.

Usage

The easiest way to try out examples is via the online demo.

Otherwise, check the building instructions below.

Setup and Build

Requirements

• Java SE Development Kit 8
• Scala Build Tool, sbt (version >=1.1.6)
• Z3 SMT solver
• Scala (version >= 2.12.6) - to run the standalone artifact

Building and Testing the Project

To compile and run the entire test suite (and see some cool synthesis results), execute from the root folder of the project:

sbt test

Compiling the Executables

Just run the following from your command line:

sbt assembly

As the result, an executable JAR-file will be produced, so you can run it as explained below.

Synthesizing Programs from SL Specifications

Alternatively, once you have built the artifact via sbt assembly, you can run it as a standalone application (given that the runnable scala is in your path).

Case Studies

At the moment, many interesting case studies can be found in the folder $PROJECT_ROOT/examples. More examples and benchmarks related to the paper on SSL are in the folders paper-examples and paper-benchmarks under $PROJECT_ROOT/src/test/resources/synthesis.

Each set of case studies is in a single folder (e.g., copy). The definitions of inductive predicates and auxiliary function specifications (lemmas) are given in the single .def-file, typically present in each such folder. For instance, in examples, it is predicates.def, whose contents are as follows:

predicate lseg(loc x, set s) {
|  x == 0        => { s =i {} ; emp }
|  not (x == 0)  => { s =i {v} ++ s1 ; [x, 2] ** x :-> v ** (x + 1) :-> nxt ** lseg(nxt, s1) }
}

predicate lseg2(loc x, set s) {
|  x == 0        => { s =i {} ; emp }
|  not (x == 0)  => { s =i {v} ++ s1 ; [x, 3] ** x :-> v ** (x + 1) :-> v + 1 ** (x + 2) :-> nxt ** lseg2(nxt, s1) }
}

...

The remaining files (*.syn) are the actual examples, each structured in the following format:

<A textual comment about what capability of the synthesizer is being assessed.>
#####
<Hoare-style specification of the synthesized procedure in SL>
#####
<Optional expected result>

For example, examples/listcopy.syn is defined as follows:

Copy a linked list

#####

{true ; r :-> x ** lseg(x, 0, S)}
void listcopy(loc r)
{true ; r :-> y ** lseg(x, 0, S) ** lseg(y, 0, S) }

#####

Trying the Synthesis with the Case Studies

To run the synthesis for a specific case study from a specific folder, execute the following script:

suslik [options] folder goalName

where the necessary arguments and options are

  folder                   a folder with the predicate definitions, lemmas, and synthesis goal file
  goalName                 a test case name (the file under the specified folder, called goalName.syn)
  -r, --trace <value>      print the entire derivation trace; default: true
  -t, --timeout <value>    timeout for the derivation; default (in milliseconds): 300000 (5 min)
  -d, --depth <value>      derivation depth; default: 100
  -a, --assert <value>     check that the synthesized result against the expected one; default: true
  -c, --maxCloseDepth <value>
                           maximum unfolding depth in the post-condition; default: 1
  -o, --maxOpenDepth <value>
                           maximum unfolding depth in the pre-condition; default: 1
  -b, --branchAbduction <value>
                           abduce conditional branches; default: false
  --commute <value>        only try commutative rule applications in one order; default: true
  --phased <value>         split rules into unfolding and flat phases; default: true
  --fail <value>           enable early failure rules; default: true
  --invert <value>         enable invertible rules; default: true
  -s, --printStats <value> print synthesis stats; default: true
  -e, --printEnv <value>   print synthesis context; default: false
  -f, --printFail <value>  print failed rule applications; default: false
  -g, --tags <value>       print predicate application tags in derivations; default: false
  -l, --log <value>        log results to a csv file; default: true
  --help                   prints this usage text

Once the synthesis is done execution statistics will be available in stats.csv.

For instance, to synthesize $PROJECT_ROOT/examples/listcopy.syn and see the derivation trace, run

suslik examples listcopy

to get the following result:

void listcopy (loc r) {
  let x2 = *r;
  if (x2 == 0) {
  } else {
    let v2 = *x2;
    let nxt2 = *(x2 + 1);
    *r = nxt2;
    listcopy(r);
    let y12 = *r;
    let y2 = malloc(2);
    *(x2 + 1) = y12;
    *r = y2;
    *(y2 + 1) = nxt2;
    *y2 = v2;
  }
}

If you are going to synthesize case studies from the provided set, you may only type the folder under $PROJECT_ROOT/src/test/resources/synthesis/ (i.e., without the full prefix of the path), e.g.:

suslik paper-examples 17-listcopy -r true

or

suslik examples swap -r false -t 800