c++ - How to inherit from std::runtime_error? -

for example:

#include <stdexcept> class { }; class err : public a, public std::runtime_error("") { }; int main() {    err x;    return 0; } 

with ("") after runtime_error get:

error: expected '{' before '(' token error: expected unqualified-id before string constant error: expected ')' before string constant 

else (without ("")) get

in constructor 'err::err()': error: no matching function call 'std::runtime_error::runtime_error()' 

what's going wrong?

(you can test here: http://www.compileonline.com/compile_cpp_online.php)

this correct syntax:

class err : public a, public std::runtime_error 

and not:

class err : public a, public std::runtime_error("") 

as doing above. if want pass empty string constructor of std::runtime_error, way:

class err : public a, public std::runtime_error { public:     err() : std::runtime_error("") { } //        ^^^^^^^^^^^^^^^^^^^^^^^^ }; 

here live example show code compiling.