On Jul 21, 2009, at 9:54 AM, Thorsten Ottosen wrote:
Sebastian Redl skrev:
Is c_str() allowed to be > O(1) ? Yes. In particular, this implementation is valid: template <...> class basic_string { Ch *real_data; mutable Ch *cstr_data; // ...
Phil Endecott wrote: public: const Ch *c_str() const { if (!cstr_data) { cstr_data = allocate(size() + 1); copy(cstr_data, size()); cstr_data[size()] = 0; } return cstr_data; } void any_modifying_function() { if(cstr_data) { deallocate(cstr_data); cstr_data = 0; } } };
But does *any* implementation actually do that? The problem is AFAIK that str[size] is valid when str is a const object.
Fwiw, the C++0X string will (probably) require the trailing null for non-const strings too: http://home.roadrunner.com/~hinnant/issue_review/lwg-active.html#876 (see A 2) And the committee knows of no implementations this will break. -Howard