http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53429
Bug #: 53429 Summary: complex::{imag,real} should be marked alwaysinline to guarantee libstdc++ binary compatibility between C++98 and C++11 Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: jyass...@gcc.gnu.org The non-const overloads of std::complex::real and std::complex::imag go from returning _Tp& to _Tp in C++98 vs C++11: http://gcc.gnu.org/viewcvs/trunk/libstdc%2B%2B-v3/include/std/complex?view=markup. libstdc++ includes explicit instantiations of operator<< and operator>> with complex arguments: http://gcc.gnu.org/viewcvs/trunk/libstdc%2B%2B-v3/src/c%2B%2B98/complex_io.cc?view=markup. These operator<< and operator>> overloads call complex::real() and complex::imag(). If those calls are inlined (which is likely), so that no weak definition of real() and imag() is exposed to users of the library, then I believe all is well. However, if the compiler decides not to inline them, then people linking libstdc++ from the other version of the language may wind up with two conflicting weak definitions of the symbols. I think marking them as alwaysinline would guarantee compatibility.