diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp index 27a6011b5..d7bde6e23 100644 --- a/src/smt/smt_context.cpp +++ b/src/smt/smt_context.cpp @@ -75,6 +75,7 @@ namespace smt { m_phase_default(false), m_conflict(null_b_justification), m_not_l(null_literal), + m_empty_clause(false), m_conflict_resolution(mk_conflict_resolution(m, *this, m_dyn_ack_manager, p, m_assigned_literals, m_watches)), m_unsat_proof(m), m_dyn_ack_manager(*this, p), @@ -2395,9 +2396,10 @@ namespace smt { m_unsat_proof = nullptr; } m_base_scopes.shrink(new_lvl); + m_empty_clause = false; } else { - m_conflict = null_b_justification; + m_conflict = m_empty_clause ? b_justification::mk_axiom() : null_b_justification; m_not_l = null_literal; } del_clauses(m_aux_clauses, s.m_aux_clauses_lim); diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h index d3735f199..ace0eaed0 100644 --- a/src/smt/smt_context.h +++ b/src/smt/smt_context.h @@ -188,9 +188,12 @@ namespace smt { // A conflict is usually a single justification. That is, a justification // for false. If m_not_l is not null_literal, then m_conflict is a - // justification for l, and the conflict is union of m_no_l and m_conflict; + // justification for l, and the conflict is union of m_not_l and m_conflict; + // m_empty_clause is set to ensure that an empty clause generated in deep scope + // levels survives to the base level. b_justification m_conflict; literal m_not_l; + bool m_empty_clause; scoped_ptr m_conflict_resolution; proof_ref m_unsat_proof; diff --git a/src/smt/smt_internalizer.cpp b/src/smt/smt_internalizer.cpp index efca6c042..b12bcc2ee 100644 --- a/src/smt/smt_internalizer.cpp +++ b/src/smt/smt_internalizer.cpp @@ -1351,6 +1351,7 @@ namespace smt { m_justifications.push_back(j); TRACE("mk_clause", tout << "empty clause... setting conflict\n";); set_conflict(j == nullptr ? b_justification::mk_axiom() : b_justification(j)); + m_empty_clause = true; SASSERT(inconsistent()); return nullptr; case 1: