C++ Custom exception throw () in constructor -

so read aren't supposed have other basic types in custom exception class because otherwise might throw exception within exception (like dream within dream). , should throw value , catch ref.

i have exception class header:

class deepthroatexception : public std::runtime_error {   public:   deepthroatexception(const char* err); // set err member err    private:   // error description   const char* err; }; 

but dont since introduces issue memory management, invisible naked eye , need use mine detector. change std::string if possible.

but there issue in first paragraph above, thought doing this:

#include <string> class deepthroatexception : public std::runtime_error {   public:   deepthroatexception(std::string err) throw(); // set err member err, no throw    private:   // error description   std::string err; }; 

is ok do?

using std::string can give bad time std::bad_alloc. problem inherent std::runtime_error, constructors can take std::string argument:

explicit runtime_error( const std::string& what_arg ); explicit runtime_error( const char* what_arg ); 

it's way because copying exceptions shall never throw, implementation allocate string , copy argument's content it. if don't want second exception being thrown, mark constructor noexcept , make sure never fails, , if ever do, program shut down immediately.

you can inherit std::runtime_error behavior constructing string constructor so:

deepthroatexception(const std::string& err) noexcept :     std::runtime_error(err) {     // ... } 

at point, can remove err data member, runtime_error give internal string can refer what().