restrict关键字在C ++中的意思是什么？ [英] What does the restrict keyword mean in C++?

问题描述

我总是不确定，restrict关键字在C ++中是什么意思？

I was always unsure, what does the restrict keyword mean in C++?

是否意味着给这个函数的两个或更多的指针不重叠？
还有什么意思？

Does it mean the two or more pointer given to the function does not overlap? What else does it mean?

推荐答案

在他的论文中，内存优化，Christer Ericson说，虽然 restrict 不是C ++标准的一部分，它由许多编译器支持，并建议在可用时使用：

In his paper, Memory Optimization, Christer Ericson says that while restrict is not part of the C++ standard yet, that it is supported by many compilers and he recommends it's usage when available:

限制关键字

restrict keyword

！新到1999年的ANSI / ISO C标准

! New to 1999 ANSI/ISO C standard

！不是在C ++标准中，但由许多C ++编译器支持

! Not in C++ standard yet, but supported by many C++ compilers

！

限制合格的指针（或引用）...

A restrict-qualified pointer (or reference)...

！ ...基本上是一个
承诺的编译器，对于
范围的指针，目标的指针将只有
通过该指针访问（和指针复制
从它）。

! ...is basically a promise to the compiler that for the scope of the pointer, the target of the pointer will only be accessed through that pointer (and pointers copied from it).

在支持它的C ++编译器中，它应该可能与C中的一样。

In C++ compilers that support it it should probably behave the same as in C.

有关详情，请参阅此SO职位：现实用法C99'restrict'关键字？

See this SO post for details: Realistic usage of the C99 ‘restrict’ keyword?

花半个小时浏览埃里克森的论文，这很有趣，值得花时间。

Take half an hour to skim through Ericson's paper, it's interesting and worth the time.

编辑

我还发现IBM的 AIX C / C ++编译器支持 __ restrict __ 关键字。

I also found that IBM's AIX C/C++ compiler supports the __restrict__ keyword.

g ++似乎也支持这一点，因为下面的程序在g ++上完全编译：

g++ also seems to support this as the following program compiles cleanly on g++:

#include <stdio.h>

int foo(int * __restrict__ a, int * __restrict__ b) {
    return *a + *b;
}

int main(void) {
    int a = 1, b = 1, c;

    c = foo(&a, &b);

    printf("c == %d\n", c);

    return 0;
}

我还发现了一个关于使用限制：

了解限制关键字

Edit2

我遇到了一篇文章，具体讨论了在C ++程序中使用restrict：

I ran across an article which specifically discusses the use of restrict in C++ programs:

Load-hit-stores and the __restrict keyword

此外，Microsoft Visual C ++ 也支持 __ restrict 关键字 。

Also, Microsoft Visual C++ also supports the __restrict keyword.

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