https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61795
--- Comment #2 from Mitsuru Kariya <kariya_mitsuru at hotmail dot com> --- I think that this behaviour is caused by r201253 (for PR57974, Comment 11). DR844 was fixed by r136694 but reverted by r201253. diff r135878 r136694 https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/std/complex?r1=135878&r2=136694 diff r199924 r201253 https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/std/complex?r1=199924&r2=201253 Moreover, I think that I mistook. > Note that this problem does not occur in std::complex<double> and > std::complex<long double> because there is no difference between > C++03 and C++11. This is not true. In C++03, the 2nd argument of std::pow can cause implicit conversions. (Because it is the trivial int type.) However, I believe that it should cause no implicit conversion in C++11. (I think so from C++11 standard text quoted above.) Therefore, I think that the sample code below should be compiled successfully in C++03 mode but should cause compilation error in C++11 mode. =================================================================== #include <complex> struct S { operator int() { return 1; } }; int main() { std::complex<double> d = std::pow(std::complex<double>(0), S()); } ===================================================================