[LLVMbugs] [Bug 20293] New: The return type of std::pow(std::complex<float>, int) should be std::complex<float>

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=20293

            Bug ID: 20293
           Summary: The return type of std::pow(std::complex<float>, int)
                    should be std::complex<float>
           Product: libc++
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: kariya_mitsuru at hotmail.com
                CC: llvmbugs at cs.uiuc.edu, mclow.lists at gmail.com
    Classification: Unclassified

With libc++, the return type of std::pow(std::complex<float>, int) is
std::complex<double>.
However, in C++03 mode, the return type of std::pow(std::complex<float>, int)
should be
std::complex<float>.


According to C++03 standard 26.2.7[lib.complex.value.ops], std::pow have an
overload
function template "template<class T> std::complex<T> std::pow(const
std::complex<T>&, int)".
So I think that the return type of std::pow(std::complex<float>, int) should be
std::complex<float> in C++03 mode.


The sample code below can show whether the return type is std::complex<float>.

===========================================================================================
#include <iostream>
#include <typeinfo>
#include <complex>

int main()
{
  std::cout << std::boolalpha
            << (typeid(std::pow(std::complex<float>(1), 1)) ==
typeid(std::complex<float>))
            << std::endl;
}
===========================================================================================
cf. http://melpon.org/wandbox/permlink/GT7RQffV1BXEOImC


Additionally, in C++03, the 2nd argument of std::pow can cause implicit
conversions.
(Because it is the trivial int type.)

Therefore, I think that the sample code below should be compiled successfully
in C++03 mode.

===========================================================================================
#include <complex>

struct S {
  operator int() { return 1; }
};

int main()
{
  std::complex<float> d = std::pow(std::complex<float>(0), S());
}
===========================================================================================
cf. http://melpon.org/wandbox/permlink/G0CEVjhnaTEMfbNs

Note that the 2nd sample should be compiled successfully with double and long
double too.

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