gmalecha / coq-smt-check

Invoke SMT solvers from Coq to check obligations

coq-smt-check

This is a simple way to invoke an SMT solver on Coq goals. It does NOT generate proof objects. It is meant purely for sanity checking goals.

The main tactic is 'smt solve' which invokes an smt on the current goal. The core of the plugin is the conversion from Coq to SMT2 format. At the moment, the conversion handles the following:

• boolean connectives, /, /, not
• equality
• variables
• real numbers, +, -, /, constants

If your problem fits in this fragment (it can contain other facts as well), then you can run:

smt solve.

If the solver solves the goal then the tactic will succeed. If the solver returns an unsat core then the tactic will act like

clear - <unsat core>.

otherwise it will simply act like idtac (doing nothing to the goal). If the solver fails to solve the goal then the tactic will fail and display the sat model if the solver returns one. A common way to use the tactic is something like the following:

smt solve; admit.

which will admit the goal only if it is solved by the SMT solver.

You can also specify the solver to use in the tactic using the syntax:

smt solve calling "<solver-name>".

Where `' is, e.g. z3 or cvc4.

See the test-suite directory for examples.

Solvers

Currently, the code supports Z3 and CVC4. You need to set the solver using

Set SMT Solver "z3".

or

Set SMT Solver "cvc4".

You can toggle debugging globally using:

Set SMT Debug.
Unset SMT Debug.

Implementing Your Own Solver

You can implement your own solver interface using a Coq Plugin. At the high level, you should call:

SmtTactic.register_smt_solver : <name> -> (<options> -> <solver>) -> unit

and then set up the solver appropriately. Note that solver names can NOT contain colons (:). The string passed will be split on the first colon (if one exists) and the rest of the string will be passed as options above.

Install from OPAM

Make sure you added the Coq repository:

opam repo add coq-released https://coq.inria.fr/opam/released

and run:

opam install coq-smt-check

Contributors

This plugin was started by Vignesh Gowada at UCSD as part of the VeriDrone project. It was updated and is currently maintained by Gregory Malecha.

External contributions are always welcome.