c++ - What does c_str() method from string class returns? -

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i want access starting address of array maintained string class.

string str="hey"; char* pointer=(char*)str.c_str();

  1. is pointer pointing address of array(maintained string class)? or string class create new array dynamic memory , copy existing string , return it's address?

  2. if not right way, how access starting address of array maintained string class?

in c++11 standard it's explicitly stated .c_str() (as newer .data()) shall return pointer internal buffer used std::string.

any modification of std::string after obtaining pointer via .c_str() may result in said char * returned became invalid (that - if std::string internally had reallocate space).

in previous c++ standards implementation allowed return anything. standard not require user deallocate result, i've never seen implementation returning newly allocated. @ least gnu gcc's , msvc++'s stl string internally zero-terminated char arrays, returned c_str().

so it's safe assume (with normal c++ caution) in version of c++ in it's implementation .c_str() return internal buffer.

in other words - should never ever keep value of .c_str() unless 100% sure it's won't change it's size anytime in future (unless it's const, is).

p.s. btw, should never ever char* pointer=(char*)str.c_str();. it's const char * , shall not modify contents, partly because above - may end-up overwriting memory of other object or corrupting internal state of std::string, in case implementation doing fancy, indexing characters faster .find()(newer seen that, hey - that's encapsulation!)


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