merge with master

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

examples/dotnet/Program.cs

@@ -2106,6 +2106,7 @@ namespace test_mapi
             Console.WriteLine("OK, model: {0}", s.Model.ToString());
         }
 
+
         public static void TranslationExample()
         {
             Context ctx1 = new Context();

examples/java/JavaExample.java

@@ -1482,7 +1482,7 @@ class JavaExample
         BoolExpr ca = commAxiom(ctx, g);
 
         BoolExpr thm = ctx.parseSMTLIB2String(
-                "(assert (forall ((x Int) (y Int)) (=> (= x y) (= (gg x 0) (gg 0 y)))))",
+                "(declare-fun (Int Int) Int) (assert (forall ((x Int) (y Int)) (=> (= x y) (= (gg x 0) (gg 0 y)))))",
                 null, null, new Symbol[] { ctx.mkSymbol("gg") },
                 new FuncDecl[] { g })[0];
         System.out.println("formula: " + thm);
@@ -2303,7 +2303,7 @@ class JavaExample
                 p.simplifierExample(ctx);
                 p.finiteDomainExample(ctx);
                 p.floatingPointExample1(ctx);
-                p.floatingPointExample2(ctx);
+                // core dumps: p.floatingPointExample2(ctx);
             }
 
             { // These examples need proof generation turned on.
@@ -2314,7 +2314,7 @@ class JavaExample
                 p.proveExample2(ctx);
                 p.arrayExample2(ctx);
                 p.tupleExample(ctx);
-                p.parserExample3(ctx);
+                // throws p.parserExample3(ctx);
                 p.enumExample(ctx);
                 p.listExample(ctx);
                 p.treeExample(ctx);

src/api/dotnet/Context.cs

@@ -2777,25 +2777,25 @@ namespace Microsoft.Z3
         /// <summary>
         /// Create an at-most-k constraint.
         /// </summary>
-        public BoolExpr MkAtMost(BoolExpr[] args, uint k)
+        public BoolExpr MkAtMost(IEnumerable<BoolExpr> args, uint k)
         {
            Contract.Requires(args != null);
            Contract.Requires(Contract.Result<BoolExpr[]>() != null);
            CheckContextMatch<BoolExpr>(args);
-           return new BoolExpr(this, Native.Z3_mk_atmost(nCtx, (uint) args.Length,
+           return new BoolExpr(this, Native.Z3_mk_atmost(nCtx, (uint) args.Count(),
-                                                          AST.ArrayToNative(args), k));
+                                                          AST.EnumToNative(args), k));
         }
 
         /// <summary>
         /// Create an at-least-k constraint.
         /// </summary>
-        public BoolExpr MkAtLeast(BoolExpr[] args, uint k)
+        public BoolExpr MkAtLeast(IEnumerable<BoolExpr> args, uint k)
         {
            Contract.Requires(args != null);
            Contract.Requires(Contract.Result<BoolExpr[]>() != null);
            CheckContextMatch<BoolExpr>(args);
-           return new BoolExpr(this, Native.Z3_mk_atleast(nCtx, (uint) args.Length,
+           return new BoolExpr(this, Native.Z3_mk_atleast(nCtx, (uint) args.Count(),
-                                                          AST.ArrayToNative(args), k));
+                                                          AST.EnumToNative(args), k));
         }
 
         /// <summary>

src/api/java/Model.java

@@ -91,11 +91,11 @@ public class Model extends Z3Object {
                     return null;
                 else
                 {
-                    if (!Native.isAsArray(getContext().nCtx(), n))
+                    if (Native.isAsArray(getContext().nCtx(), n)) {
-                        throw new Z3Exception(
+                      long fd = Native.getAsArrayFuncDecl(getContext().nCtx(), n);
-                                "Argument was not an array constant");
+                      return getFuncInterp(new FuncDecl(getContext(), fd));
-                    long fd = Native.getAsArrayFuncDecl(getContext().nCtx(), n);
+                    }
-                    return getFuncInterp(new FuncDecl(getContext(), fd));
+		    return null;
                 }
             } else
             {

src/ast/bv_decl_plugin.h

@@ -354,6 +354,8 @@ public:
     MATCH_BINARY(is_bv_mul);
     MATCH_BINARY(is_bv_sle);
     MATCH_BINARY(is_bv_ule);
+    MATCH_BINARY(is_bv_ashr);
+    MATCH_BINARY(is_bv_lshr);
     MATCH_BINARY(is_bv_shl);
     MATCH_BINARY(is_bv_urem);
     MATCH_BINARY(is_bv_srem);

src/ast/pb_decl_plugin.cpp

@@ -92,7 +92,7 @@ func_decl * pb_decl_plugin::mk_func_decl(decl_kind k, unsigned num_parameters, p
 }
 
 void pb_decl_plugin::get_op_names(svector<builtin_name> & op_names, symbol const & logic) {
-    if (logic == symbol::null || logic == "QF_FD" || logic == "ALL") {
+    if (logic == symbol::null || logic == "QF_FD" || logic == "ALL" || logic == "HORN") {
         op_names.push_back(builtin_name(m_at_most_sym.bare_str(), OP_AT_MOST_K));
         op_names.push_back(builtin_name(m_at_least_sym.bare_str(), OP_AT_LEAST_K));
         op_names.push_back(builtin_name(m_pble_sym.bare_str(), OP_PB_LE));

src/cmd_context/basic_cmds.cpp

@@ -59,7 +59,7 @@ public:
         if (c == nullptr) {
             std::string err_msg("unknown command '");
             err_msg = err_msg + s.bare_str() + "'";
-            throw cmd_exception(err_msg);
+            throw cmd_exception(std::move(err_msg));
         }
         m_cmds.push_back(s);
     }
@@ -384,7 +384,7 @@ class set_option_cmd : public set_get_option_cmd {
             std::string msg = "error setting '";
             msg += opt_name.str();
             msg += "', option value cannot be modified after initialization";
-            throw cmd_exception(msg);
+            throw cmd_exception(std::move(msg));
         }
     }
 

src/cmd_context/check_logic.cpp

@@ -17,6 +17,7 @@ Revision History:
 
 --*/
 #include "cmd_context/check_logic.h"
+#include "solver/smt_logics.h"
 #include "ast/arith_decl_plugin.h"
 #include "ast/array_decl_plugin.h"
 #include "ast/bv_decl_plugin.h"
@@ -453,7 +454,7 @@ struct check_logic::imp {
         else if (fid == m_dt_util.get_family_id() && m_dt) {
             // nothing to check
         }
-        else if (fid == m_pb_util.get_family_id() && m_logic == "QF_FD") {
+        else if (fid == m_pb_util.get_family_id() && smt_logics::logic_has_pb(m_logic)) {
             // nothing to check
         }
         else {

src/cmd_context/cmd_context.cpp

@@ -369,7 +369,7 @@ void stream_ref::set(char const * name) {
             std::string msg = "failed to set output stream '";
             msg += name;
             msg += "'";
-            throw cmd_exception(msg);
+            throw cmd_exception(std::move(msg));
         }
         SASSERT(m_stream);
     }

src/muz/fp/horn_tactic.cpp

@@ -211,7 +211,7 @@ class horn_tactic : public tactic {
                 default:
                     msg << "formula is not in Horn fragment: " << mk_pp(g->form(i), m) << "\n";
                     TRACE("horn", tout << msg.str(););
-                    throw tactic_exception(msg.str().c_str());
+                    throw tactic_exception(msg.str());
                 }
             }
 

src/parsers/smt2/smt2parser.cpp

@@ -909,7 +909,7 @@ namespace smt2 {
                     std::string err_msg = "invalid datatype declaration, unknown sort '";
                     err_msg += missing.str();
                     err_msg += "'";
-                    throw parser_exception(err_msg, line, pos);
+                    throw parser_exception(std::move(err_msg), line, pos);
                 }
                 dts->commit(pm());
                 m_ctx.insert_aux_pdecl(dts.get());
@@ -989,7 +989,7 @@ namespace smt2 {
                 std::string err_msg = "invalid datatype declaration, unknown sort '";
                 err_msg += missing.str();
                 err_msg += "'";
-                throw parser_exception(err_msg, line, pos);
+                throw parser_exception(std::move(err_msg), line, pos);
             }
         }
 
@@ -999,7 +999,7 @@ namespace smt2 {
                 std::string err_msg = "invalid datatype declaration, repeated accessor identifier '";
                 err_msg += duplicated.str();
                 err_msg += "'";
-                throw parser_exception(err_msg, line, pos);
+                throw parser_exception(std::move(err_msg), line, pos);
             }
         }
 

src/qe/nlqsat.cpp

@@ -844,8 +844,7 @@ namespace qe {
                 break;
             case l_undef:
                 result.push_back(in.get());
-                std::string s = "search failed";
+                throw tactic_exception("search failed");
-                throw tactic_exception(s.c_str()); 
             }        
         }
 

src/qe/qsat.cpp

@@ -1279,7 +1279,7 @@ namespace qe {
                 if (s == "ok" || s == "unknown") {
                     s = m_fa.s().reason_unknown();
                 }
-                throw tactic_exception(s.c_str()); 
+                throw tactic_exception(std::move(s));
             }        
         }
         
@@ -1344,7 +1344,7 @@ namespace qe {
                     s = m_fa.s().reason_unknown();
                 }
 
-                throw tactic_exception(s.c_str()); 
+                throw tactic_exception(std::move(s));
             }        
             return l_true;
         }

src/sat/tactic/goal2sat.cpp

@@ -92,7 +92,7 @@ struct goal2sat::imp {
 
     void throw_op_not_handled(std::string const& s) {
         std::string s0 = "operator " + s + " not supported, apply simplifier before invoking translator";
-        throw tactic_exception(s0.c_str());
+        throw tactic_exception(std::move(s0));
     }
     
     void mk_clause(sat::literal l) {

src/smt/tactic/smt_tactic.cpp

@@ -39,7 +39,6 @@ class smt_tactic : public tactic {
     smt_params                   m_params;
     params_ref                   m_params_ref;
     statistics                   m_stats;
-    std::string                  m_failure;
     smt::kernel *                m_ctx;
     symbol                       m_logic;
     progress_callback *          m_callback;
@@ -259,7 +258,7 @@ public:
                 if (m_fail_if_inconclusive && !m_candidate_models) {
                     std::stringstream strm;
                     strm << "smt tactic failed to show goal to be sat/unsat " << m_ctx->last_failure_as_string();
-                    throw tactic_exception(strm.str().c_str());
+                    throw tactic_exception(strm.str());
                 }
                 result.push_back(in.get());
                 if (m_candidate_models) {
@@ -281,8 +280,7 @@ public:
                         break;
                     }
                 }
-                m_failure = m_ctx->last_failure_as_string();
+                throw tactic_exception(m_ctx->last_failure_as_string());
-                throw tactic_exception(m_failure.c_str());
             }
         }
         catch (rewriter_exception & ex) {

src/smt/theory_pb.cpp

@@ -752,9 +752,10 @@ namespace smt {
     class theory_pb::card_justification : public justification {
         card& m_card;
         family_id m_fid;
+        literal m_lit;
     public:
-        card_justification(card& c, family_id fid)
+        card_justification(card& c, literal lit, family_id fid)
-            : justification(true), m_card(c), m_fid(fid) {}
+            : justification(true), m_card(c), m_fid(fid), m_lit(lit) {}
 
         card& get_card() { return m_card; }
 
@@ -769,7 +770,28 @@ namespace smt {
             return m_fid;
         }
         
-        virtual proof* mk_proof(smt::conflict_resolution& cr) { return 0; }
+        virtual proof* mk_proof(smt::conflict_resolution& cr) { 
+            ptr_buffer<proof> prs;
+            ast_manager& m = cr.get_context().get_manager(); 
+            expr_ref fact(m);
+            cr.get_context().literal2expr(m_lit, fact);
+            bool all_valid = true;
+            proof* pr = nullptr;
+            pr = cr.get_proof(m_card.lit());
+            all_valid &= pr != nullptr;
+            prs.push_back(pr);
+            for (unsigned i = m_card.k(); i < m_card.size(); ++i) {
+                pr = cr.get_proof(~m_card.lit(i));
+                all_valid &= pr != nullptr;
+                prs.push_back(pr);
+            }
+            if (!all_valid) {
+                return nullptr;
+            }
+            else {
+                return m.mk_th_lemma(m_fid, fact, prs.size(), prs.c_ptr());
+            }
+        }
 
 
     };
@@ -959,7 +981,7 @@ namespace smt {
         m_stats.m_num_propagations++;
         TRACE("pb", tout << "#prop: " << c.num_propagations() << " - " << c.lit() << " => " << l << "\n";);
         SASSERT(validate_unit_propagation(c));
-        ctx.assign(l, ctx.mk_justification(card_justification(c, get_id())));
+        ctx.assign(l, ctx.mk_justification(card_justification(c, l, get_id())));
     }
 
     void theory_pb::clear_watch(card& c) {

src/smt/theory_seq.cpp

@@ -5036,7 +5036,7 @@ expr* theory_seq::coalesce_chars(expr* const& e) {
         if (bvu.is_bv(s)) {
             expr_ref result(m);
             expr * args[1] = {s};
-            if (m_seq_rewrite.mk_app_core(to_app(e)->get_decl(), 1, args, result)) {
+            if (BR_FAILED != m_seq_rewrite.mk_app_core(to_app(e)->get_decl(), 1, args, result)) {
                 if (!ctx.e_internalized(result))
                     ctx.internalize(result, false);
                 return result;

src/solver/parallel_tactic.cpp

@@ -635,7 +635,7 @@ private:
             t.join();
         m_manager.limit().reset_cancel();
         if (m_exn_code == -1) 
-            throw default_exception(m_exn_msg);
+            throw default_exception(std::move(m_exn_msg));
         if (m_exn_code != 0) 
             throw z3_error(m_exn_code);            
         if (!m_models.empty()) {

src/solver/smt_logics.cpp

@@ -150,7 +150,7 @@ bool smt_logics::logic_has_horn(symbol const& s) {
 }
 
 bool smt_logics::logic_has_pb(symbol const& s) {
-    return s == "QF_FD" || s == "ALL";
+    return s == "QF_FD" || s == "ALL" || logic_has_horn(s);
 }
 
 bool smt_logics::logic_has_datatype(symbol const& s) {

src/tactic/arith/pb2bv_tactic.cpp

@@ -968,7 +968,7 @@ private:
         void throw_tactic(expr* e) {
             std::stringstream strm;
             strm << "goal is in a fragment unsupported by pb2bv. Offending expression: " << mk_pp(e, m);
-            throw tactic_exception(strm.str().c_str());
+            throw tactic_exception(strm.str());
         }
     };
 

src/tactic/core/reduce_invertible_tactic.cpp

@@ -30,7 +30,9 @@ Notes:
 #include "tactic/core/reduce_invertible_tactic.h"
 #include "tactic/core/collect_occs.h"
 #include "tactic/generic_model_converter.h"
+#include <cstdint>
 
+namespace {
 class reduce_invertible_tactic : public tactic {
     ast_manager& m;
     bv_util      m_bv;
@@ -60,7 +62,8 @@ public:
         generic_model_converter_ref mc;
         occs(*g, vars);
         expr_safe_replace sub(m);
-        expr_ref p(m), new_v(m);
+        expr_ref new_v(m);
+        expr * p;
         for (expr* v : vars) {
             if (is_invertible(v, p, new_v, &mc)) {
                 mark_inverted(p);
@@ -75,8 +78,8 @@ public:
             expr_ref f_new(m);
             sub(f, f_new);
             rw(f_new, f_new);
-            proof_ref new_pr(m);
             if (f == f_new) continue;
+            proof_ref new_pr(m);
             if (g->proofs_enabled()) {
                 proof * pr = g->pr(idx);
                 new_pr     = m.mk_modus_ponens(pr, new_pr);
@@ -120,11 +123,20 @@ private:
         }
     }
 
-    // store up to two parents of expression.
+    // store one parent of expression, or null if multiple
     struct parents {
-        parents(): m_p1(nullptr), m_p2(nullptr) {}
+        parents(): m_p(0) {}
-        expr* m_p1;
+        uintptr_t m_p;
-        expr* m_p2;
+
+        void set(expr * e) {
+            SASSERT((uintptr_t)e != 1);
+            if (!m_p) m_p = (uintptr_t)e;
+            else m_p = 1;
+        }
+
+        expr * get() const {
+          return m_p == 1 ? nullptr : (expr*)m_p;
+        }
     };
     svector<parents> m_parents;
     struct parent_collector {
@@ -132,9 +144,8 @@ private:
         parent_collector(reduce_invertible_tactic& c):c(c) {}
         void operator()(app* n) {
             for (expr* arg : *n) {
-                c.m_parents.reserve(arg->get_id() + 1, parents());
+                c.m_parents.reserve(arg->get_id() + 1);
-                parents& p = c.m_parents[arg->get_id()];
+                c.m_parents[arg->get_id()].set(n);
-                if (!p.m_p1) p.m_p1 = n; else p.m_p2 = n;
             }
         }
         void operator()(expr*) {}
@@ -156,11 +167,13 @@ private:
 
     // TBD: could be made to be recursive, by walking multiple layers of parents.
     
-    bool is_invertible(expr* v, expr_ref& p, expr_ref& new_v, generic_model_converter_ref* mc) {
+    bool is_invertible(expr* v, expr*& p, expr_ref& new_v, generic_model_converter_ref* mc) {
-        p = m_parents[v->get_id()].m_p1;
+        p = m_parents[v->get_id()].get();
-        if (m_parents[v->get_id()].m_p2 || !p) return false;
+        SASSERT(p);
+
         if (m_inverted.is_marked(p)) return false;
         if (mc && !is_ground(p)) return false;
+
         if (m_bv.is_bv_add(p)) {
             if (mc) {
                 ensure_mc(mc);
@@ -175,6 +188,24 @@ private:
             new_v = v;
             return true;
         }
+
+        expr *a, *b;
+        // shift(a, b), where both a,b are single use. Set b = 0 and return a
+        // FIXME: needs to check that both variables are grounded by same quantifier
+        if (m_bv.is_bv_shl(p, a, b) ||
+            m_bv.is_bv_ashr(p, a, b) ||
+            m_bv.is_bv_lshr(p, a, b)) {
+            if (!m_parents[(v == a ? b : a)->get_id()].get())
+                return false;
+
+            if (mc) {
+                ensure_mc(mc);
+                (*mc)->add(b, m_bv.mk_numeral(rational::zero(), get_sort(b)));
+            }
+            new_v = a;
+            return true;
+        }
+
         if (m_bv.is_bv_mul(p)) {
             expr_ref rest(m);
             for (expr* arg : *to_app(p)) {
@@ -365,7 +396,8 @@ private:
             expr_safe_replace sub(m);
             t.m_parents.reset();
             t.m_inverted.reset();
-            expr_ref p(m), new_v(m);
+            expr_ref new_v(m);
+            expr * p;
             
             {
                 parent_collector proc(t);           
@@ -409,11 +441,9 @@ private:
             rewriter_tpl<reduce_q_rw_cfg>(t.m, false, m_cfg),
             m_cfg(t) {}
     };
-
-
 };
+}
 
 tactic * mk_reduce_invertible_tactic(ast_manager & m, params_ref const &) {
     return alloc(reduce_invertible_tactic, m);
 }
-

src/tactic/tactic.cpp

@@ -206,7 +206,7 @@ void fail_if_proof_generation(char const * tactic_name, goal_ref const & in) {
     if (in->proofs_enabled()) {
         std::string msg = tactic_name;
         msg += " does not support proof production";
-        throw tactic_exception(msg.c_str());
+        throw tactic_exception(std::move(msg));
     }
 }
 
@@ -214,7 +214,7 @@ void fail_if_unsat_core_generation(char const * tactic_name, goal_ref const & in
     if (in->unsat_core_enabled()) {
         std::string msg = tactic_name;
         msg += " does not support unsat core production";
-        throw tactic_exception(msg.c_str());
+        throw tactic_exception(std::move(msg));
     }
 }
 
@@ -222,6 +222,6 @@ void fail_if_model_generation(char const * tactic_name, goal_ref const & in) {
     if (in->models_enabled()) {
         std::string msg = tactic_name;
         msg += " does not generate models";
-        throw tactic_exception(msg.c_str());
+        throw tactic_exception(std::move(msg));
     }
 }

src/tactic/tactic_exception.h

@@ -26,7 +26,7 @@ class tactic_exception : public z3_exception {
 protected:
     std::string m_msg;
 public:
-    tactic_exception(char const * msg):m_msg(msg) {}
+    tactic_exception(std::string && msg) : m_msg(std::move(msg)) {}
     ~tactic_exception() override {}
     char const * msg() const override { return m_msg.c_str(); }
 };

src/tactic/tactical.cpp

@@ -463,9 +463,9 @@ public:
         if (finished_id == UINT_MAX) {
             switch (ex_kind) {
             case ERROR_EX: throw z3_error(error_code);
-            case TACTIC_EX: throw tactic_exception(ex_msg.c_str());
+            case TACTIC_EX: throw tactic_exception(std::move(ex_msg));
             default:
-                throw default_exception(ex_msg.c_str());
+                throw default_exception(std::move(ex_msg));
             }
         }
     }    
@@ -660,9 +660,9 @@ public:
             if (failed) {
                 switch (ex_kind) {
                 case ERROR_EX: throw z3_error(error_code);
-                case TACTIC_EX: throw tactic_exception(ex_msg.c_str());
+                case TACTIC_EX: throw tactic_exception(std::move(ex_msg));
                 default:
-                    throw default_exception(ex_msg.c_str());
+                    throw default_exception(std::move(ex_msg));
                 }
             }
 

src/util/cmd_context_types.h

@@ -55,8 +55,8 @@ class cmd_exception : public default_exception {
     }
 public:
     cmd_exception(char const * msg):default_exception(msg), m_line(-1), m_pos(-1) {}
-    cmd_exception(std::string const & msg):default_exception(msg), m_line(-1), m_pos(-1) {}
+    cmd_exception(std::string && msg):default_exception(std::move(msg)), m_line(-1), m_pos(-1) {}
-    cmd_exception(std::string const & msg, int line, int pos):default_exception(msg), m_line(line), m_pos(pos) {}
+    cmd_exception(std::string && msg, int line, int pos):default_exception(std::move(msg)), m_line(line), m_pos(pos) {}
     cmd_exception(char const * msg, symbol const & s): 
         default_exception(compose(msg,s)),m_line(-1),m_pos(-1) {}
     cmd_exception(char const * msg, symbol const & s, int line, int pos): 

src/util/gparams.cpp

@@ -356,7 +356,7 @@ public:
             }
         }
         if (error)
-            throw exception(error_msg);
+            throw exception(std::move(error_msg));
     }
 
     std::string get_value(params_ref const & ps, symbol const & p) {
@@ -417,7 +417,7 @@ public:
             }
         }
         if (error)
-            throw exception(error_msg);
+            throw exception(std::move(error_msg));
         return r;
     }
 
@@ -509,7 +509,7 @@ public:
             }
         }
         if (error)
-            throw exception(error_msg);
+            throw exception(std::move(error_msg));
     }
 
     void display_parameter(std::ostream & out, char const * name) {
@@ -550,7 +550,7 @@ public:
             }
         }
         if (error)
-            throw exception(error_msg);
+            throw exception(std::move(error_msg));
     }
 };
 

src/util/lp/lp_utils.h

@@ -49,6 +49,7 @@ bool contains(const std::unordered_map<A, B> & map, const A& key) {
 #endif
 
 namespace lp {
+
 inline void throw_exception(const std::string & str) {
     throw default_exception(str);
 }

src/util/timeout.cpp

@@ -27,9 +27,10 @@ Revision History:
 #include "util/event_handler.h"
 #include "util/scoped_timer.h"
 
-scoped_timer * g_timeout = nullptr;
+static scoped_timer * g_timeout = nullptr;
-void (* g_on_timeout)() = nullptr;
+static void (* g_on_timeout)() = nullptr;
 
+namespace {
 class g_timeout_eh : public event_handler {
 public:
     void operator()(event_handler_caller_t caller_id) override {
@@ -46,6 +47,7 @@ public:
         }
     }
 };
+}
 
 void set_timeout(long ms) {
     if (g_timeout) 

src/util/z3_exception.cpp

@@ -67,9 +67,6 @@ default_exception::default_exception(fmt, char const* msg, ...) {
     m_msg = out.str();
 }
 
-default_exception::default_exception(std::string const & msg): m_msg(msg) {
-}
-
 char const * default_exception::msg() const { 
     return m_msg.c_str(); 
 }

src/util/z3_exception.h

@@ -41,7 +41,7 @@ class default_exception : public z3_exception {
     std::string m_msg;
 public:
     struct fmt {};
-    default_exception(std::string const& msg);
+    default_exception(std::string && msg) : m_msg(std::move(msg)) {}
     default_exception(fmt, char const* msg, ...);
     ~default_exception() override {}
     char const * msg() const override;