How Can I Extend the Lifetime of Temporary Objects in C Using Const References?

Binding Temporary Objects to Const References

In C , temporary objects typically expire at the end of the expression in which they appear, potentially leading to dangling references. However, the language offers a unique feature that allows extending the lifetime of temporaries when bound to const references.

The following code demonstrates this concept:

<code class="cpp">string foo() {
  return string("123");
}

int main() {
  const string& val = foo();
  printf("%s\n", val.c_str());
  return 0;
}</code>

Despite foo() returning a temporary string, the assignment to the const reference val prolongs the temporary's lifetime until the reference itself expires. This is intended behavior as per the C standard, ensuring that val always points to a valid object.

However, it's important to note that this exception only applies to stack-based references. References that are members of objects do not extend the lifetime of their bound temporary objects. For more details on this feature, refer to Herb Sutter's "GotW #88: A Candidate For the “Most Important const”."

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