c++ - No dangling reference for std::min in libc++ -

it known (or should be) binding result of std::min const reference bad idea, whenever 1 of arguments of std::min rvalue, since const reference binding not propagated through function return. following code

#include <iostream> #include <algorithm>  int main() {     int n = 42;     const int& r = std::min(n - 1, n + 1); // r dangling after line     std::cout << r; } 

should produce undefined behaviour since r dangling. , indeed, when compiling gcc5.2 -wall -o3 compiler spits

warning: <anonymous> used uninitialized in function [-wuninitialized]

however, compiling clang (llvm 7.0.0) using same flags (even including -wextra) not emit warning, , program seems "work", i.e. displays 41.

question: clang using "safe" version of std::min? version uses sfinae return value whenever 1 of arguments rvalue? or not required emit diagnostic , program "happens" produce "right" result in ub scenario?

it ub. libc++ not protect in way.