http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55002
Bug #: 55002 Summary: trailing return type is rejected in function signature Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: leo...@volnitsky.com 7.1.6.4 auto specifier [dcl.spec.auto] note 2: The auto type-specifier may appear with a function declarator with a trailing-return-type (8.3.5) in any context where such a declarator is valid Contrived example: ------------------------------------------------------------- typedef unsigned long size_t; // overload c-array template<class T, size_t N> size_t size(T (&)[N]) { return N; } // overload - c-string template<size_t N> size_t size(char (&A)[N]) { size_t i=0; while(A[i++]); return i; } // APPLY // this works template<class T, size_t N> size_t apply (const T (&A)[N], size_t (*f) (const T (&)[N])) // this rejected -- error: parameter declared ‘auto’ //template<class T, size_t N> size_t apply (const T (&A)[N], auto (*f) -> size_t (const T (&)[N])) { return f(A); }; int main() { int A[2]; return apply(A, size); } ------------------------------------------------------------------ Without trailing return type in signature it is impossible to write apply-like function with can deduce function-type for overloaded functions.