What is the meaning of auto main()-int?

Question

I happened to come across the below code snippet in a video on C++11, where the author uses ``` auto main()->int ``` I didn't understand this. I tried to compile in `g++` using `-std=c++11` and it works. Can somebody explain to me what is going on here? I tried to search using "auto main()->int" but didn't find any help.

Accepted Answer

C++11 introduced a notation for trailing return types: If a function declaration is introduced with `auto`, the return type will be specified after the parameters and a `->` sequence. That is, all that does is to declare `main()` to return `int`.

The significance of trailing return types is primarily for function template where it is now possible to use parameters to the function together with `decltype()` to determine the return type. For example:

```
template <typename M, typename N>
auto multiply(M const& m, N const& n) -> decltype(m * n);
```

This declares the function `multiply()` to return the type produced by `m * n`. Putting the use of `decltype()` in front of `multiply()` would be invalid because `m` and `n` are not, yet, declared.

Although it is primarily useful for function template, the same notation can also be used for other function. With C++14 the trailing return type can even be omitted when the function is introduced with `auto` under some conditions.

What is the meaning of auto main()->int?

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