强制内联函数在其他翻译单元 [英] force inline function in other translation unit

问题描述

在gcc手册的这一部分是pretty模糊，反复尝试后，我无法理解的forceinline属性的用法。

This part of the gcc manual is pretty obscure and i can't understand the usage of the forceinline attribute after repeated attempts.

我定义对象和特定功能来操纵该对象。很少有这些功能可以使用原子操作，我想编译器内联这些函数。但是我不想写这些函数在头文件，并用静态内联就像在Linux内核中声明它们。

I'm defining an object and certain functions to manipulate that object. Few of those functions can use atomic instructions and i want the compiler to inline those functions. However i do not want to write those functions in the header file and declare them with "static inline" like in the linux kernel.

有没有办法迫使GCC从另一个转换单元内联函数？

Is there a way to force gcc to inline functions from another translation unit ?

推荐答案

您可以使用 always_inline 属性，例如：

you can use the always_inline attribute, for example:

void foo () __attribute__((always_inline));

从文档

always_inline
      一般来说，除非指定优化功能不内联。对于函数声明为内联，此属性的内联
  即使没有指定优化级别的功能。

always_inline Generally, functions are not inlined unless optimization is specified. For functions declared inline, this attribute inlines the function even if no optimization level was specified.

注1 ：有没有必要使用在线如果您使用 always_inline 属性

Note1: There's no need to use inline if you use the always_inline attribute

注2 ：如果函数不能被内联，你会得到一个警告，例如，如果在编译时的定义不可用，但是，在一个更​​高的优化GCC还可以内联入呼叫者，有一个为太具体的开关：

Note2: If the function could not be inlined you will get a warning, if for example the definition is not available when compiling, however, at a higher optimization gcc can still inline it into the caller, there's a specific switch for that too:

-funit-at-a-time

从文档：

优化级别-O2以上，特别是，使
  单位在-A-时间模式，其中的允许编译器要考虑的信息
  编译函数时从文件后面的功能获得。
  编译一次多个文件到一个输出文件
  单位在-A-时间模式可让编译器使用从获得的信息
  所有的文件汇编他们每个人当

Optimization levels -O2 and above, in particular, enable unit-at-a-time mode, which allows the compiler to consider information gained from later functions in the file when compiling a function. Compiling multiple files at once to a single output file in unit-at-a-time mode allows the compiler to use information gained from all of the files when compiling each of them.

注3 ：
这是没有必要有一个明确的原型，因此您可以在功能确定指标使用属性：

Note3: It is not necessary to have an explicit prototype so you can use the attribute on the function defintion:

__attribute__((always_inline)) void foo() {
   //some code
}

另请参阅此讨论，它回答大家的一些问题。

Also see this discussion, it answers some of your questions.

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