CODEWITHSUNDEEP
c++overloadingrvalue-reference
olist
olist

Reputation: 1039

const/non-const rvalue reference in overload resolution

#include <iostream>
#include <string>

using namespace std;

void func(string &&a) { cout << "#1" << endl; }
void func(const string &&a) { cout << "#2" << endl; }
void func(int &&a) { cout << "#3" << endl; }
void func(const int &&a) { cout << "#4" << endl; }

int main()
{
  func(string("1"));                // call func(string &&) 
  func((const string)string("1"));  // call func(const string &&)
  func(1);                          // call func(int &&)
  func((const int)1);               // call func(int &&) not func(const int &&)

  return 0;
}

From the C++ standard:

Standard conversion sequence S1 is a better conversion sequence than standard conversion sequence S2 if
...
S1 and S2 are reference bindings (8.5.3), and the types to which the references refer are the same type except for top-level cv-qualifiers, and the type to which the reference initialized by S2 refers is more cv-qualified than the type to which the reference initialized by S1 refers.

It seems that the last call doesn't behave as expected. Who can explain it for me?

Upvotes: 2

Views: 166

Answers (1)

cpplearner
cpplearner

Reputation: 15823

The type of (const int)1 is adjusted to int before overload resolution.

[expr]/6:

If a prvalue initially has the type “cv T”, where T is a cv-unqualified non-class, non-array type, the type of the expression is adjusted to T prior to any further analysis.

Upvotes: 1

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