C（99）和C ++（11）之间不兼容的区别是什么？ [英] What are the incompatible differences between C(99) and C++(11)?
问题描述
此问题是由回复的帖子触发的由Herb Sutter 解释，MS决定不支持/不制作C99编译器，而无论如何都要使用C ++（11）标准中的C（99）功能。
This question was triggered by replie(s) to a post by Herb Sutter where he explained MS's decision to not support/make a C99 compiler but just go with the C(99) features that are in the C++(11) standard anyway.
一个评论员回答：
（...）C很重要，至少应引起一点注意。
(...) C is important and deserves at least a little bit of attention.
有很多现有代码是有效的C，但不是
有效的C ++。该代码不太可能被重写（...）
There is a LOT of existing code out there that is valid C but is not valid C++. That code is not likely to be rewritten (...)
由于我只在MS C ++中编程，所以我真的不知道纯 C很好，即我不了解我正在使用的C ++语言的哪些细节不在C（99）中，而且我几乎看不出某些C99代码无法按原样在C ++中工作的线索编译器。
Since I only program in MS C++, I really don't know "pure" C that well, i.e. I have no ready picture of what details of the C++-language I'm using are not in C(99) and I have little clues where some C99 code would not work as-is in a C++ compiler.
请注意，我了解C99仅 restrict 关键字，对我来说似乎具有非常狭窄的应用程序，并且关于可变长度数组（我不确定它们的广泛性或重要性）。
Note that I know about the C99 only restrict keyword which to me seems to have very narrow application and about variable-length-arrays (of which I'm not sure how widespread or important they are).
此外，我对是否有任何重要的语义差异或陷阱，即C（99）代码将在C ++（11）下进行编译，但是在C ++编译器中所做的事情与在C编译器中有所不同。
Also, I'm very interested whether there are any important semantic differences or gotchas, that is, C(99) code that will compile under C++(11) but do something differently with the C++ compiler than with the C compiler.
快速链接：答案中的外部资源：
Quick links: External resources from the answers:
- Wikipedia页面
- David R. Tribble的比较（从2001年开始）
- C ++ 11标准：http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/ n3376.pdf （第C.1节）
- Wikipedia page
- David R. Tribble's comparison (from 2001)
- C++11 standard: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3376.pdf (section C.1)
推荐答案
如果您从C和C ++的公共子集开始，有时称为clean C（不是完全C90），则必须考虑三种不兼容类型：
If you start from the common subset of C and C++, sometimes called clean C (which is not quite C90), you have to consider 3 types of incompatibilities:
-
使合法C非法C ++的其他C ++功能
例如C ++关键字，可以用作C中的标识符或C中的隐式转换，但需要在C ++中进行显式转换。
Examples for this are C++ keywords which can be used as identifiers in C or conversions which are implicit in C but require an explicit cast in C++.
这可能是Microsoft仍然完全提供C前端的主要原因：否则，必须重写不能作为C ++编译的旧代码。
This is probably the main reason why Microsoft still ships a C frontend at all: otherwise, legacy code that doesn't compile as C++ would have to be rewritten.
不属于C ++的其他C功能
在C ++被派生之后，C语言并没有停止发展。例如可变长度数组，指定的初始化程序和 restrict 。这些功能可能非常方便，但不是任何C ++标准的一部分，其中一些可能永远都不会使用。
The C language did not stop evolving after C++ was forked. Some examples are variable-length arrays, designated initializers and restrict. These features can be quite handy, but aren't part of any C++ standard, and some of them will probably never make it in.
功能
An example for this would be the linkage of const objects or inline functions.
这样的例子是 const的链接对象或内联函数。
A list of incompatibilities between C99 and C++98 can be found here (which has already been mentioned by Mat).
C99和C ++ 98之间的不兼容列表可在此处找到（Mat已经提到过）
While C++11 and C11 got closer on some fronts (variadic macros are now available in C++, variable-length arrays are now an optional C language feature), the list of incompatibilities has grown as well (eg generic selections in C and the auto type-specifier in C++).
尽管C ++ 11和C11在某些方面越来越紧密（可变宏数组现在在C ++中可用，可变长度数组现在是C语言的可选功能），不兼容列表也在增加（例如，C语言中的泛型选择和C ++语言中的 auto 类型说明符）。
As an aside, while Microsoft has taken some heat for the decision to abandon C (which is not a recent one), as far as I know no one in the open source community has actually taken steps to do something about it: It would be quite possible to provide many features of modern C via a C-to-C++ compiler, especially if you consider that some of them are trivial to implement. This is actually possible right now using Comeau C/C++, which does support C99.
但是，这并不是一个紧迫的问题：就我个人而言，我对使用它非常满意Windows上的GCC和Clang，以及MSVC的专有替代品，例如Pelles C或Intel的编译器。
However, it's not really a pressing issue: Personally, I'm quite comfortable with using GCC and Clang on Windows, and there are proprietary alternatives to MSVC as well, eg Pelles C or Intel's compiler.
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