复合文字标准C ++？ [英] Are compound literals Standard C++?

问题描述

复合字面是一个C99结构。即使我可以在C ++中这样做：

Compound Literals are a C99 construct. Even though I can do this in C++ :

#include <iostream>
using namespace std;

int main() {
    for (auto i : (float[2]) {2.7, 3.1}) cout << i << endl;
}

似乎例如MSVC支持它附加信息。然而所有的编译器我可以得到我的手，编译上面提到的代码。

It seems that for example MSVC supports it as an extension. Yet all compilers I can get my hands on, compile the above mentioned code.

因此是C ++ 14中的一项功能吗？是否有不同的标准术语（在我看来，只是创建一个临时使用支撑的初始化）？

So is this a feature available in C++14 ? Is there a different standard term (It looks to me like just creating a temporary using braced initialization) ?

侧注：复合文字（或任何我应该称为上述内容）是包扩展上下文（

Side Note : "Compound Literals" (or whatever I should call the above) are a pack expansion context ( just to mention a functionality )

推荐答案

这是一个扩展， gcc 和 clang 支持。 gcc文档说：

This is an extension that both gcc and clang support. The gcc document says:

作为扩展，GCC支持C90模式和C ++中的复合文字，虽然语义在C ++ 。

As an extension, GCC supports compound literals in C90 mode and in C++, though the semantics are somewhat different in C++.

如果您使用 -pedantic 您应该会收到警告，例如 clang 说（ 查看实时 ）：

if you build with -pedantic you should receive a warning, for example clang says (see it live):

警告：复合文字是C99特定功能[-Wc99-extensions]

warning: compound literals are a C99-specific feature [-Wc99-extensions]

请注意，C ++中的语义差异并不重要，在C99中定义的代码在C ++中有这个扩展的未定义的行为：

Note, the semantic differences in C++ are not minor and code that would be well-defined in C99 can have undefined behavior in C++ with this extension:

在C ++中，复合字面值指定一个临时对象，其完全表达式的结束。因此，取得复合字面值的子对象的地址的定义良好的
C代码可以在C ++中未定义
。

In C++, a compound literal designates a temporary object, which only lives until the end of its full-expression. As a result, well-defined C code that takes the address of a subobject of a compound literal can be undefined in C++.

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