dvecompile: implement maybe check using exception handling (setjmp).

tools/dvecompile.h

@@ -119,7 +119,7 @@ struct dve_compiler: public dve_explicit_system_t
     void write_bound_check_C(dve_expression_t & expr, std::ostream & ostr, std::string state_name);
     void write_maybe_check_C(dve_expression_t & expr, std::ostream & ostr, std::string state_name);
 
-    void write_C(dve_expression_t & expr, std::ostream & ostr, std::string state_name);
+    void write_C(dve_expression_t & expr, std::ostream & ostr, std::string state_name, bool wrap);
 
     bool m_if_disjoint;
     bool m_if_empty;
@@ -146,7 +146,7 @@ struct dve_compiler: public dve_explicit_system_t
     void if_cexpr_clause( dve_expression_t *expr, std::string state ) {
         if (!expr)
             return;
-        if_clause( cexpr( *expr, state ) );
+        if_clause( cexpr( *expr, state, false ) );
     }
 
     void if_end() {
@@ -200,10 +200,10 @@ struct dve_compiler: public dve_explicit_system_t
     }
 
     std::string cmaybe( dve_expression_t &expr, std::string state );
-    std::string cexpr( dve_expression_t &expr, std::string state );
+    std::string cexpr( dve_expression_t &expr, std::string state, bool wrap );
     void print_cexpr( dve_expression_t &expr, std::string state )
     {
-        line( cexpr( expr, state ) + ";" );
+        line( cexpr( expr, state, false ) + ";" );
     }
 
     void new_label() {