__attribute __((force))的作用是什么? [英] What does the __attribute__((force)) do?

问题描述

听起来我应该可以使用Google，但找不到很好的参考. __attribute__((force))到底是做什么的?如:

 return (__attribute__((force)) uint32_t) *p

(这是针对使用clang交叉编译的ARM系统，但是即使在clang/arm特定页面中，我也找不到此属性的任何引用.)

解决方案

__attribute__((force))用于抑制稀疏(Linux内核的c语义检查器)中的警告.

稀疏的维基百科文章列出了稀疏定义的以下属性:

• address_space(num)
• 按位
• 力
• 上下文(表达式，in_context，out_context)

如果需要有关这些的更多信息，可以查看 sparse的手册页

在Linux内核中，某些属性在中重新定义linux/include/linux/compiler_types.h .例如，__force扩展为__attribute__((force))或__bitwise扩展为__attribute__((bitwise)).

但是关于稀疏的Linux文档告诉我们，gcc会忽略以下属性:

使用gcc，所有"__按位"/"__ force的东西"都消失了，所有这些最终看起来就像gcc的整数一样.

This sounds like something I should be able to Google, but I can't find a good reference. What exactly does __attribute__((force)) do? As in:

 return (__attribute__((force)) uint32_t) *p

(this is for an ARM system, cross compiled with clang, but I can't find any reference anywhere on this attribute even in clang/arm specific pages..).

解决方案

__attribute__((force)) is used to suppress warnings in sparse, the c semantics checker of the linux kernel.

The wikipedia article of sparse lists the following attributes as defined by sparse:

• address_space(num)
• bitwise
• force
• context(expression,in_context,out_context)

If you need more information about these, you can take a look at the man page of sparse

In the linux kernel some these attributes are redefined in linux/include/linux/compiler_types.h. For example __force expands to __attribute__((force)) or __bitwise to __attribute__((bitwise)).

However the linux documentation about sparse tells us, that gcc ignores these attributes:

And with gcc, all the "__bitwise"/"__force stuff" goes away, and it all ends up looking just like integers to gcc.

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