std::string vs. char*

Question

does std::string store data differently than a char* on either stack or heap or is it just derived from char* into a class?

Answer 1

char*

• Is the size of one pointer for your CPU architecture.
• May be a value returned from malloc or calloc or new or new[].
  • If so, must be passed to free or delete or delete[] when you're done.
  • If so, the characters are stored on the heap.
• May result from "decomposition" of a char[ N ] (constant N) array or string literal.
  • Generically, no way to tell if a char* argument points to stack, heap, or global space.
• Is not a class type. It participates in expressions but has no member functions.
• Nevertheless implements the RandomAccessIterator interface for use with and such.

std::string

• Is the size of several pointers, often three.
• Constructs itself when created: no need for new or delete.
  • Owns a copy of the string, if the string may be altered.
  • Can copy this string from a char*.
  • By default, internally uses new[] much as you would to obtain a char*.
• Provides for implicit conversion which makes transparent the construction from a char* or literal.
• Is a class type. Defines other operators for expressions such as catenation.
  • Defines c_str() which returns a char* for temporary use.
• Implements std::string::iterator type with begin() and end().
  • string::iterator is flexible: an implementation may make it a range-checked super-safe debugging helper or simply a super-efficient char* at the flip of a switch.