diff --git a/src/ast/datatype_decl_plugin.cpp b/src/ast/datatype_decl_plugin.cpp
index 284c4df93..9cb685ccc 100644
--- a/src/ast/datatype_decl_plugin.cpp
+++ b/src/ast/datatype_decl_plugin.cpp
@@ -231,7 +231,7 @@ namespace datatype {
                 }
                 return s;
             }
-            catch (invalid_datatype) {
+            catch (const invalid_datatype &) {
                 m_manager->raise_exception("invalid datatype");
                 return nullptr;
             }
diff --git a/src/ast/for_each_expr.cpp b/src/ast/for_each_expr.cpp
index d46388801..311133e05 100644
--- a/src/ast/for_each_expr.cpp
+++ b/src/ast/for_each_expr.cpp
@@ -58,7 +58,7 @@ bool has_skolem_functions(expr * n) {
     try {
         for_each_expr(p, n);
     }
-    catch (has_skolem_functions_ns::found) {
+    catch (const has_skolem_functions_ns::found &) {
         return true;
     }
     return false;
diff --git a/src/ast/occurs.cpp b/src/ast/occurs.cpp
index c76e73748..9ddb2fa56 100644
--- a/src/ast/occurs.cpp
+++ b/src/ast/occurs.cpp
@@ -58,7 +58,7 @@ bool occurs(expr * n1, expr * n2) {
     try {
         quick_for_each_expr(p, n2);
     }
-    catch (occurs_namespace::found) {
+    catch (const occurs_namespace::found &) {
         return true;
     }
     return false;
@@ -69,7 +69,7 @@ bool occurs(func_decl * d, expr * n) {
     try {
         quick_for_each_expr(p, n);
     }
-    catch (occurs_namespace::found) {
+    catch (const occurs_namespace::found &) {
         return true;
     }
     return false;
diff --git a/src/cmd_context/check_logic.cpp b/src/cmd_context/check_logic.cpp
index 57e15c6a3..47c919d4a 100644
--- a/src/cmd_context/check_logic.cpp
+++ b/src/cmd_context/check_logic.cpp
@@ -476,7 +476,7 @@ struct check_logic::imp {
             quick_for_each_expr(*this, n);
             return true;
         }
-        catch (failed) {
+        catch (const failed &) {
             return false;
         }
     }
@@ -495,7 +495,7 @@ struct check_logic::imp {
             check_sort(f->get_range());
             return true;
         }
-        catch (failed) {
+        catch (const failed &) {
             return false;
         }
     }
diff --git a/src/cmd_context/cmd_context.cpp b/src/cmd_context/cmd_context.cpp
index 8a23f80a0..7b7f81561 100644
--- a/src/cmd_context/cmd_context.cpp
+++ b/src/cmd_context/cmd_context.cpp
@@ -1833,7 +1833,7 @@ void cmd_context::validate_model() {
                     for_each_expr(contains_underspecified, a);
                     for_each_expr(contains_underspecified, r);
                 }
-                catch (contains_underspecified_op_proc::found) {
+                catch (const contains_underspecified_op_proc::found &) {
                     continue;
                 }
                 TRACE("model_validate", model_smt2_pp(tout, *this, *md, 0););
diff --git a/src/math/polynomial/algebraic_numbers.cpp b/src/math/polynomial/algebraic_numbers.cpp
index aa4fc5a39..528c10537 100644
--- a/src/math/polynomial/algebraic_numbers.cpp
+++ b/src/math/polynomial/algebraic_numbers.cpp
@@ -1989,7 +1989,7 @@ namespace algebraic_numbers {
                     TRACE("anum_eval_sign", tout << "all variables are assigned to rationals, value of p: " << r << "\n";);
                     return qm().sign(r);
                 }
-                catch (opt_var2basic::failed) {
+                catch (const opt_var2basic::failed &) {
                     // continue
                 }
 
diff --git a/src/math/polynomial/polynomial.cpp b/src/math/polynomial/polynomial.cpp
index 24658fdcf..00a4d0593 100644
--- a/src/math/polynomial/polynomial.cpp
+++ b/src/math/polynomial/polynomial.cpp
@@ -4493,7 +4493,7 @@ namespace polynomial {
                         }
                         #endif
                     }
-                    catch (sparse_mgcd_failed) {
+                    catch (const sparse_mgcd_failed &) {
                         flet<bool> use_prs(m_use_prs_gcd, false);
                         gcd_prs(u, v, x, r);
                     }
diff --git a/src/math/subpaving/tactic/subpaving_tactic.cpp b/src/math/subpaving/tactic/subpaving_tactic.cpp
index 935fd5e19..7a3f2e7b3 100644
--- a/src/math/subpaving/tactic/subpaving_tactic.cpp
+++ b/src/math/subpaving/tactic/subpaving_tactic.cpp
@@ -183,7 +183,7 @@ class subpaving_tactic : public tactic {
                     process_clause(g.form(i));
                 }
             }
-            catch (subpaving::exception) {
+            catch (const subpaving::exception &) {
                 throw tactic_exception("failed to internalize goal into subpaving module");
             }
         }
@@ -195,7 +195,7 @@ class subpaving_tactic : public tactic {
             try {
                 (*m_ctx)();
             }
-            catch (subpaving::exception) {
+            catch (const subpaving::exception &) {
                 throw tactic_exception("failed building subpaving tree...");
             }
             if (m_display) {
diff --git a/src/muz/base/dl_rule.cpp b/src/muz/base/dl_rule.cpp
index 0dbeba5b3..fe1f101b1 100644
--- a/src/muz/base/dl_rule.cpp
+++ b/src/muz/base/dl_rule.cpp
@@ -422,7 +422,7 @@ namespace datalog {
         try {
             quick_for_each_expr(proc, fml);
         }
-        catch (contains_predicate_proc::found) {
+        catch (const contains_predicate_proc::found &) {
             return true;
         }
         return false;
diff --git a/src/muz/base/hnf.cpp b/src/muz/base/hnf.cpp
index f0cbc0620..1e6196950 100644
--- a/src/muz/base/hnf.cpp
+++ b/src/muz/base/hnf.cpp
@@ -219,7 +219,7 @@ private:
             quick_for_each_expr(m_proc, m_mark1, fml);
             m_mark1.reset();
         }
-        catch (contains_predicate_proc::found) {
+        catch (const contains_predicate_proc::found &) {
             m_mark1.reset();
             return true;
         }
diff --git a/src/muz/spacer/spacer_context.cpp b/src/muz/spacer/spacer_context.cpp
index 30b68ebf6..9a9043f2f 100644
--- a/src/muz/spacer/spacer_context.cpp
+++ b/src/muz/spacer/spacer_context.cpp
@@ -2737,7 +2737,7 @@ lbool context::solve(unsigned from_lvl)
             // }
         }
         VERIFY (validate ());
-    } catch (unknown_exception)
+    } catch (const unknown_exception &)
     {}
 
     if (m_last_result == l_true) {
diff --git a/src/muz/spacer/spacer_farkas_learner.cpp b/src/muz/spacer/spacer_farkas_learner.cpp
index d97bee49f..291226b55 100644
--- a/src/muz/spacer/spacer_farkas_learner.cpp
+++ b/src/muz/spacer/spacer_farkas_learner.cpp
@@ -95,7 +95,7 @@ bool farkas_learner::is_pure_expr(func_decl_set const& symbs, expr* e, ast_manag
     is_pure_expr_proc proc(symbs, m);
     try {
         for_each_expr(proc, e);
-    } catch (is_pure_expr_proc::non_pure) {
+    } catch (const is_pure_expr_proc::non_pure &) {
         return false;
     }
     return true;
diff --git a/src/muz/spacer/spacer_iuc_proof.cpp b/src/muz/spacer/spacer_iuc_proof.cpp
index b6a522b76..949507fb4 100644
--- a/src/muz/spacer/spacer_iuc_proof.cpp
+++ b/src/muz/spacer/spacer_iuc_proof.cpp
@@ -88,7 +88,7 @@ bool iuc_proof::is_core_pure(expr* e) const
     try {
         for_each_expr(proc, e);
     }
-    catch (is_pure_expr_proc::non_pure)
+    catch (const is_pure_expr_proc::non_pure &)
     {return false;}
 
     return true;
diff --git a/src/muz/spacer/spacer_manager.cpp b/src/muz/spacer/spacer_manager.cpp
index 856207463..817d620c9 100644
--- a/src/muz/spacer/spacer_manager.cpp
+++ b/src/muz/spacer/spacer_manager.cpp
@@ -247,7 +247,7 @@ bool has_zk_const(expr *e){
     try {
         for_each_expr(p, e);
     }
-    catch (has_zk_const_ns::found) {
+    catch (const has_zk_const_ns::found &) {
         return true;
     }
     return false;
diff --git a/src/muz/spacer/spacer_quant_generalizer.cpp b/src/muz/spacer/spacer_quant_generalizer.cpp
index a11ab4d9e..f3307a596 100644
--- a/src/muz/spacer/spacer_quant_generalizer.cpp
+++ b/src/muz/spacer/spacer_quant_generalizer.cpp
@@ -120,7 +120,7 @@ struct index_lt_proc : public std::binary_function<app*, app *, bool> {
             for (expr *e : v)
                 quick_for_each_expr(fn, visited, e);
         }
-        catch (has_nlira_functor::found ) {
+        catch (const has_nlira_functor::found &) {
             return true;
         }
         return false;
diff --git a/src/muz/spacer/spacer_util.cpp b/src/muz/spacer/spacer_util.cpp
index ec01218f1..2a5f1e2cc 100644
--- a/src/muz/spacer/spacer_util.cpp
+++ b/src/muz/spacer/spacer_util.cpp
@@ -891,7 +891,7 @@ namespace {
             for_each_expr(cs, fml);
             return false;
         }
-        catch(found) {
+        catch(const found &) {
             return true;
         }
     }
diff --git a/src/muz/tab/tab_context.cpp b/src/muz/tab/tab_context.cpp
index c60c770bf..b5be996dc 100644
--- a/src/muz/tab/tab_context.cpp
+++ b/src/muz/tab/tab_context.cpp
@@ -415,7 +415,7 @@ namespace tb {
             try {
                 quick_for_each_expr(p, t);
             }
-            catch (non_constructor) {
+            catch (const non_constructor &) {
                 return false;
             }
             return true;
diff --git a/src/muz/transforms/dl_mk_elim_term_ite.cpp b/src/muz/transforms/dl_mk_elim_term_ite.cpp
index f0d9a8843..7e0356e7e 100644
--- a/src/muz/transforms/dl_mk_elim_term_ite.cpp
+++ b/src/muz/transforms/dl_mk_elim_term_ite.cpp
@@ -57,7 +57,7 @@ namespace {
         term_ite_proc f(m);
         try {
             quick_for_each_expr(f, e);
-        } catch (term_ite_proc::found) {
+        } catch (const term_ite_proc::found &) {
             return true;
         }
         return false;
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index ff37bfa95..d9c3457fa 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -706,7 +706,7 @@ namespace opt {
                 quick_for_each_expr(proc, visited, f);
             }
         }
-        catch (is_bv::found) {
+        catch (const is_bv::found &) {
             return false;
         }
         return true;
@@ -737,7 +737,7 @@ namespace opt {
         try {
             quick_for_each_expr(proc, visited, p);
         }
-        catch (is_propositional_fn::found) {
+        catch (const is_propositional_fn::found &) {
             return false;
         }
         return true;
diff --git a/src/parsers/smt2/smt2parser.cpp b/src/parsers/smt2/smt2parser.cpp
index 1a16b817b..58b16717d 100644
--- a/src/parsers/smt2/smt2parser.cpp
+++ b/src/parsers/smt2/smt2parser.cpp
@@ -3084,7 +3084,7 @@ namespace smt2 {
                                            << ": " << ex.msg() << "\")" << std::endl;
                     exit(ex.error_code());
                 }
-                catch (stop_parser_exception) {
+                catch (const stop_parser_exception &) {
                     m_scanner.stop_caching();
                     return !found_errors;
                 }
diff --git a/src/parsers/util/simple_parser.cpp b/src/parsers/util/simple_parser.cpp
index c9d00ebcc..48c42c240 100644
--- a/src/parsers/util/simple_parser.cpp
+++ b/src/parsers/util/simple_parser.cpp
@@ -118,7 +118,7 @@ bool simple_parser::parse(std::istream & in, expr_ref & result) {
         if (!result)
             throw parser_error();
     }
-    catch (parser_error) {
+    catch (const parser_error &) {
         warning_msg("parser error");
         return false;
     } 
diff --git a/src/qe/qe_datatypes.cpp b/src/qe/qe_datatypes.cpp
index 5499d638d..7ade47458 100644
--- a/src/qe/qe_datatypes.cpp
+++ b/src/qe/qe_datatypes.cpp
@@ -61,7 +61,7 @@ namespace qe {
                     project_nonrec(model, vars, lits);
                 }
             }
-            catch (cant_project) {
+            catch (const cant_project &) {
                 TRACE("qe", tout << "can't project:" << mk_pp(var, m) << "\n";);
                 return false;
             }
diff --git a/src/qe/qe_term_graph.cpp b/src/qe/qe_term_graph.cpp
index faa9cfed8..97b044f5b 100644
--- a/src/qe/qe_term_graph.cpp
+++ b/src/qe/qe_term_graph.cpp
@@ -62,7 +62,7 @@ namespace qe {
             is_pure_ns::proc v(is_var);
             quick_for_each_expr(v, e);
         }
-        catch (is_pure_ns::found) {
+        catch (const is_pure_ns::found &) {
             return false;
         }
         return true;
diff --git a/src/sat/sat_bdd.cpp b/src/sat/sat_bdd.cpp
index bd1745765..e7b0632d8 100644
--- a/src/sat/sat_bdd.cpp
+++ b/src/sat/sat_bdd.cpp
@@ -87,7 +87,7 @@ namespace sat {
             try {
                 return apply_rec(arg1, arg2, op);
             }
-            catch (mem_out) {
+            catch (const mem_out &) {
                 try_reorder();
                 if (!first) throw;
                 first = false;
@@ -546,7 +546,7 @@ namespace sat {
             try {
                 return bdd(mk_not_rec(b.root), this);
             }
-            catch (mem_out) {
+            catch (const mem_out &) {
                 try_reorder();
                 if (!first) throw;
                 first = false;
@@ -575,7 +575,7 @@ namespace sat {
             try {
                 return bdd(mk_ite_rec(c.root, t.root, e.root), this); 
             }
-            catch (mem_out) {
+            catch (const mem_out &) {
                 try_reorder();
                 if (!first) throw;
                 first = false;
diff --git a/src/sat/sat_solver.cpp b/src/sat/sat_solver.cpp
index f48ac57a6..2032445ed 100644
--- a/src/sat/sat_solver.cpp
+++ b/src/sat/sat_solver.cpp
@@ -1147,7 +1147,7 @@ namespace sat {
 
             }
         }
-        catch (abort_solver) {
+        catch (const abort_solver &) {
             m_reason_unknown = "sat.giveup";
             return l_undef;
         }
diff --git a/src/smt/smt_model_checker.cpp b/src/smt/smt_model_checker.cpp
index 02b0e16be..58158ec06 100644
--- a/src/smt/smt_model_checker.cpp
+++ b/src/smt/smt_model_checker.cpp
@@ -261,7 +261,7 @@ namespace smt {
         try {
             for_each_expr(*this, m_visited, n);
         }
-        catch (is_model_value) {
+        catch (const is_model_value &) {
             return true;
         }
         return false;
diff --git a/src/smt/smt_model_finder.cpp b/src/smt/smt_model_finder.cpp
index b8b22b067..30ea7b18e 100644
--- a/src/smt/smt_model_finder.cpp
+++ b/src/smt/smt_model_finder.cpp
@@ -177,7 +177,7 @@ namespace smt {
                 try {
                     for_each_expr(*this, m_visited, n);
                 }
-                catch (is_model_value) {
+                catch (const is_model_value &) {
                     return true;
                 }
                 return false;
@@ -2892,7 +2892,7 @@ namespace smt {
                 try {
                     for_each_expr(oc, m_visited, def);
                 }
-                catch (occurs) {
+                catch (const occurs &) {
                     return false;
                 }
                 return true;
@@ -2981,7 +2981,7 @@ namespace smt {
                     try {
                         process(f);
                     }
-                    catch (found_satisfied_subset) {
+                    catch (const found_satisfied_subset &) {
                         set_interp();
                         copy_non_satisfied(qcandidates, new_qs);
                         return true;
diff --git a/src/smt/uses_theory.cpp b/src/smt/uses_theory.cpp
index 517951a7b..64565dc78 100644
--- a/src/smt/uses_theory.cpp
+++ b/src/smt/uses_theory.cpp
@@ -41,7 +41,7 @@ bool uses_theory(expr * n, family_id fid, expr_mark & visited) {
     try {
         for_each_expr(p, visited, n);
     }
-    catch (uses_theory_ns::found) {
+    catch (const uses_theory_ns::found &) {
         return true;
     }
     return false;
diff --git a/src/tactic/arith/bv2real_rewriter.cpp b/src/tactic/arith/bv2real_rewriter.cpp
index 5839ff7a2..67fca873e 100644
--- a/src/tactic/arith/bv2real_rewriter.cpp
+++ b/src/tactic/arith/bv2real_rewriter.cpp
@@ -89,7 +89,7 @@ bool bv2real_util::contains_bv2real(expr* e) const {
     try {
         for_each_expr(p, e);
     }
-    catch (contains_bv2real_proc::found) {
+    catch (const contains_bv2real_proc::found &) {
         return true;
     }
     return false;
diff --git a/src/tactic/arith/fix_dl_var_tactic.cpp b/src/tactic/arith/fix_dl_var_tactic.cpp
index 669ded49d..d198ce498 100644
--- a/src/tactic/arith/fix_dl_var_tactic.cpp
+++ b/src/tactic/arith/fix_dl_var_tactic.cpp
@@ -226,7 +226,7 @@ class fix_dl_var_tactic : public tactic {
                 }
                 return most_occs();
             }
-            catch (failed) {
+            catch (const failed &) {
                 return nullptr;
             }
         }
diff --git a/src/tactic/arith/lia2pb_tactic.cpp b/src/tactic/arith/lia2pb_tactic.cpp
index db1c22866..c177f35be 100644
--- a/src/tactic/arith/lia2pb_tactic.cpp
+++ b/src/tactic/arith/lia2pb_tactic.cpp
@@ -156,7 +156,7 @@ class lia2pb_tactic : public tactic {
                 }
                 return true;
             }
-            catch (failed) {
+            catch (const failed &) {
                 return false;
             }
         }
diff --git a/src/tactic/arith/pb2bv_tactic.cpp b/src/tactic/arith/pb2bv_tactic.cpp
index f36e3a6db..7a64c9f16 100644
--- a/src/tactic/arith/pb2bv_tactic.cpp
+++ b/src/tactic/arith/pb2bv_tactic.cpp
@@ -1034,7 +1034,7 @@ struct is_pb_probe : public probe {
             
             return true;
         }
-        catch (pb2bv_tactic::non_pb) {
+        catch (const pb2bv_tactic::non_pb &) {
             return false;
         }
     }
diff --git a/src/tactic/bv/bv1_blaster_tactic.cpp b/src/tactic/bv/bv1_blaster_tactic.cpp
index b81bc5687..bf9ca4101 100644
--- a/src/tactic/bv/bv1_blaster_tactic.cpp
+++ b/src/tactic/bv/bv1_blaster_tactic.cpp
@@ -371,7 +371,7 @@ class bv1_blaster_tactic : public tactic {
                     for_each_expr_core<visitor, expr_fast_mark1, false, true>(proc, visited, f);
                 }
             }
-            catch (not_target) {
+            catch (const not_target &) {
                 return false;
             }
             return true;
diff --git a/src/tactic/goal.h b/src/tactic/goal.h
index 4125fab99..fa2f16eb6 100644
--- a/src/tactic/goal.h
+++ b/src/tactic/goal.h
@@ -195,7 +195,7 @@ bool test(goal const & g, Predicate & proc) {
         for (unsigned i = 0; i < sz; i++)
             quick_for_each_expr(proc, visited, g.form(i));
     }
-    catch (typename Predicate::found) {
+    catch (const typename Predicate::found &) {
         return true;
     }
     return false;
diff --git a/src/tactic/probe.cpp b/src/tactic/probe.cpp
index dcd1dc500..432c9d123 100644
--- a/src/tactic/probe.cpp
+++ b/src/tactic/probe.cpp
@@ -524,7 +524,7 @@ public:
             }
             return false;
         }
-        catch (found) {
+        catch (const found &) {
             return true;
         }
     }
@@ -554,7 +554,7 @@ public:
             }
             return false;
         }
-        catch (found) {
+        catch (const found &) {
             return true;
         }
     }
diff --git a/src/tactic/ufbv/ufbv_rewriter.cpp b/src/tactic/ufbv/ufbv_rewriter.cpp
index ee8a4605b..66a26be00 100644
--- a/src/tactic/ufbv/ufbv_rewriter.cpp
+++ b/src/tactic/ufbv/ufbv_rewriter.cpp
@@ -870,7 +870,7 @@ bool ufbv_rewriter::match_subst::match_args(app * lhs, expr * const * args) {
                 m_cache.insert(p);
                 continue;
             }
-            catch (match_args_aux_proc::no_match) {
+            catch (const match_args_aux_proc::no_match &) {
                 return false;
             }
         }