Expose API to convert solver into SMT-LIB2 format (#267)

Expose API to convert solver into SMT-LIB2 format

z3/src/solver.rs

@@ -309,6 +309,43 @@ impl<'ctx> Solver<'ctx> {
             )
         }
     }
+
+    pub fn to_smt2(&self) -> String {
+        let name = CString::new("benchmark generated from rust API").unwrap();
+        let logic = CString::new("").unwrap();
+        let status = CString::new("unknown").unwrap();
+        let attributes = CString::new("").unwrap();
+        let assumptions = self.get_assertions();
+        let mut num_assumptions = assumptions.len() as u32;
+        let formula = if num_assumptions > 0 {
+            num_assumptions -= 1;
+            assumptions[num_assumptions as usize].z3_ast
+        } else {
+            ast::Bool::from_bool(self.ctx, true).z3_ast
+        };
+        let z3_assumptions = assumptions.iter().map(|a| a.z3_ast).collect::<Vec<_>>();
+
+        let p = unsafe {
+            Z3_benchmark_to_smtlib_string(
+                self.ctx.z3_ctx,
+                name.as_ptr(),
+                logic.as_ptr(),
+                status.as_ptr(),
+                attributes.as_ptr(),
+                num_assumptions,
+                z3_assumptions.as_ptr(),
+                formula,
+            )
+        };
+        if p.is_null() {
+            return String::new();
+        }
+        unsafe { CStr::from_ptr(p) }
+            .to_str()
+            .ok()
+            .map(|s| s.to_string())
+            .unwrap_or_else(String::new)
+    }
 }
 
 impl<'ctx> fmt::Display for Solver<'ctx> {

z3/tests/lib.rs

@@ -258,6 +258,20 @@ fn test_solver_new_from_smtlib2() {
     assert_eq!(solver.check(), SatResult::Sat);
 }
 
+#[test]
+fn test_solver_to_smtlib2() {
+    let cfg = Config::new();
+    let ctx = Context::new(&cfg);
+    let solver1 = Solver::new(&ctx);
+    let t1 = ast::Bool::from_bool(&ctx, true);
+    let t2 = ast::Bool::from_bool(&ctx, true);
+    solver1.assert(&t1._eq(&t2));
+    let s1_smt2 = solver1.to_smt2();
+    let solver2 = Solver::new(&ctx);
+    solver2.from_string(s1_smt2);
+    assert_eq!(solver2.check(), solver1.check());
+}
+
 #[test]
 fn test_solver_translate() {
     let cfg = Config::new();