Why does assigning stringstream::str().c_str() to a const char* result in a runtime error?

Conversion Confusion: understanding the behavior of stringstream, string, and char*

The quandary revolving around stringstream, string, and char* conversion arises from the transient nature of the string returned by stringstream.str().c_str(). This temporary string, existing only within the expression's lifespan, is susceptible to deletion upon statement completion.

As demonstrated in the provided code snippet, assigning the temporary string to a const char* leads to a runtime error, as the pointer references memory that has been released. The resulting garbage output is a manifestation of this memory referencing error.

To prevent this issue, one can either copy the temporary string to a more permanent location, such as another string object, before obtaining the C string representation. Alternatively, the temporary string's lifetime can be extended by binding it to a const reference, as shown below:

{
  const std::string& tmp = stringstream.str();
  const char* cstr = tmp.c_str();
}

This approach ensures that the string remains accessible throughout the scope of the reference.

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