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c++clangc++14variable-templates
Tory Webster
Tory Webster

Reputation: 365

Clang auto variable template bug

I went to see if you could use auto in a variable template declaration.

template <typename T>
auto F = T{};

Fine, but as soon as you try to use it, clang craps.

int f = F<int>; // error: cannot initialize a variable of type 'int' with an lvalue of type 'auto'
auto f = F<int>; // Stacktrace
decltype(F<int>) f = F<int>; // StackFace
std::cout << std::is_same<int, decltype(F<int>)>::value; // false
std::cout << typeid(decltype(F<int>)).name(); // Stacktrace
std::cout << std::is_same<decltype(F<int>), decltype(F<int>)>::value; // true

Any combination of decltype(auto), auto doesn't work even though it says that auto is an lvalue. 

int f = static_cast<int>(F<int>); // error: static_cast from 'auto' to 'int' is not allowed

I've never seen auto act this way before. Is it because of variable templates or because of how clang treats auto?

Upvotes: 4

Views: 330

Answers (1)

Kevin Ushey
Kevin Ushey

Reputation: 21315

This seems to be addressed in the latest version of clang; putting that into a file and calling 

clang++ -std=c++1y test.cpp

gives me no errors.

kevinushey@Kevin-MBP:~$ clang++ -v
clang version 3.5 (trunk 201469)
Target: x86_64-apple-darwin13.0.0
Thread model: posix

Upvotes: 1

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