On Fri, Aug 28, 2015 at 8:59 AM, Jonathan Wakely <jwak...@redhat.com> wrote: > There seems to be no need to construct a std::string here, just pass a > const char* (see below).
To be honest, I wasn't considering performance for a bit, since exceptions are already considered slow by me :P. But yes, we can do less allocations. > I wonder if we want to make this more efficient by adding a private > member to regex_error that would allow information to be appended to > the string, rather then creating a new regex_error with a new string. I can add a helper function to _Scanner to construct the exception object for only once. For functions that can't access this helper, use return value for error handling. > I suggest adding another overload that takes a const char* rather than > std::string. The reason is that when using the new ABI this function > will take a std::__cxx11::string, so calling it will allocate memory > for the string data, then that string is passed to the regex_error > constructor which has to convert it internally to an old std::string, > which has to allocate a second time. First, to make it clear: due to _M_get_location_string(), we need dynamic allocation. So is it good to have an owned raw pointer stored in runtime_error, pointing to a heap allocated char chunk, which will be deallocated in regex_error's dtor? -- Regards, Tim Shen
