C++ type deduction of overloaded function

Asked Aug 09 '19 at 23:38

Active Aug 10 '19 at 00:55

Viewed 115 times

Is this legal code?

#include <utility>
#include <iostream>

int main() {
    const auto func2 = std::swap<int>;
}

This code seems legal to me. But the compilers don't agree with each other. GCC is happy with it, but clang gives an error.

prog.cc:8:16: error: variable 'func2' with type 'const auto' has incompatible initializer of type '<overloaded function type>'
const auto func2 = std::swap<int>;
           ^       ~~~~~~~~~~~~~~

So, I'm confused. Can anyone explain?

I'm using clang 9.0.0 on wandbox:

clang++ prog.cc -Wall -Wextra -I/opt/wandbox/boost-1.70.0/clang-6.0.1/include -std=c++17

edited Aug 10 '19 at 00:55

asked Aug 09 '19 at 23:38

Yang Yang

3

I believe it's undefined behavior to take the address of a standard function. – David G Aug 09 '19 at 23:40
@0x499602D2 but why the compiler is not happy with that?? – TonySalimi Aug 09 '19 at 23:52
Is that the entire error message? Often the compiler follows the error message with some notes that give more details. – Pete Becker Aug 10 '19 at 00:47
@PeteBecker. Now it has the entire error message. – Yang Yang Aug 10 '19 at 00:53
@0x499602D2 It is "unspecified (possibly ill-formed)", except for some I/O manipulators. – 1201ProgramAlarm Aug 10 '19 at 00:55
This seems to be an issue with the latest clang and ``. – 1201ProgramAlarm Aug 10 '19 at 01:01
Okay; the compiler really isn’t helping here. – Pete Becker Aug 10 '19 at 01:06
3

[Can I take the address of a function defined in standard library?](https://stackoverflow.com/q/55687044/995714) – phuclv Aug 10 '19 at 01:07
Note there is more than one `swap` overload. In particular, we have the array overload. – L. F. Aug 10 '19 at 08:15
Per phuclv, possible duplicate of [Can I take the address of a function defined in standard library?](https://stackoverflow.com/questions/55687044/can-i-take-the-address-of-a-function-defined-in-standard-library) – Davis Herring Aug 10 '19 at 14:28
The funny thing is, that it happily compiles with clang-HEAD (or 8/7/6) on godbolt: https://godbolt.org/z/3spfoa. – ead Aug 10 '19 at 20:27

C++ type deduction of overloaded function

0 Answers0