自动类型归纳函数返回值

Question

I am watching Scott Meyers's online video and have a different result with his presentation. Here is the code:

auto LookupValue(int i) {
    static vector<int> values = {1, 2, 3, 4, 5};
    return values[i];
}

I got a waring for the return line with the information: 'Returning 'int&' from a function returning 'void''. Why the returning value deduce to void?

Here is my testbed:

fetag@MacgicBox ~$ clang --version
Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

just a quick update: I test the return value as follows, and the compile DO set the return type with integral and should be returned by value, because of only the last line output with 1, the others are all 0.

cout << is_lvalue_reference<decltype(LookupValue(2))>::value << endl;
cout << is_rvalue_reference<decltype(LookupValue(2))>::value << endl;
cout << is_reference<decltype(LookupValue(2))>::value << endl;
cout << is_pointer<decltype(LookupValue(2))>::value << endl;
cout << is_void<decltype(LookupValue(2))>::value << endl;
cout << is_integral<decltype(LookupValue(2))>::value << endl;

Update conclusion: Finally, this is a bug of the parse component of CLion, and they promise to fix it in the next release. Here is the bug report and feedback:

https://youtrack.jetbrains.com/issue/CPP-9906

Answer 1

Why the returning value deduce to void?

The compiler made a mistake. It should deduce int, not void.

... Or the example isn't complete.