__attribute __（（init_priority（X））） [英] __attribute__((init_priority(X))) in GCC

问题描述

我在GCC中使用 __ attribute __（（init_priority（X））），如下所示：

I'm using __attribute__((init_priority(X))) in GCC like this:

Type1 __attribute__ ((init_priority (101))) name1 = value1;
Type2 __attribute__ ((init_priority (102))) name2 = value2;

。让我们说file1.cpp和file2.cpp。
如果我在同一个库中使用它的工作原理，name1在name2之前初始化，但是如果我在不同的库中使用它，初始化的顺序不是预期的顺序。我读gcc文档，这应该在不同的库中工作，我期望，定义初始化的顺序。在使用这个方式有什么问题吗？你有同样的问题吗？

in different source files. Let's say file1.cpp and file2.cpp. If I use this in same library it works as expected, name1 is initialized before name2 but if I use this in different libraries the order of initialization is not the expected one. I read on gcc documentation that this should work in different libraries as I expect, to define the order of initialization. Is there something wrong in the way I use this? Did you have same problem?

PS：重构不是解决这个问题，因为我必须从Visual Studio移植一个非常大的项目。

PS: refactoring is not a solution for this problem because I must port a very big project from Visual Studio.

推荐答案

gcc文档（gcc 4.4）说：

The gcc documentation (gcc 4.4) says:

< init_priority（PRIORITY）'

`init_priority (PRIORITY)'

在标准C ++中，保证在命名空间范围中定义的对象
被严格按照
它们在给定翻译单元中的定义 。对于跨翻译单位的初始化，不保证是
。但是，GNU
C ++允许用户控制对象初始化的顺序
在命名空间范围中使用`init_priority'属性定义
指定相对PRIORITY，一个常数整数表达式
目前约在101和65535之间。较低的数字
表示较高的优先级。

In Standard C++, objects defined at namespace scope are guaranteed to be initialized in an order in strict accordance with that of their definitions in a given translation unit. No guarantee is made for initializations across translation units. However, GNU C++ allows users to control the order of initialization of objects defined at namespace scope with the `init_priority' attribute by specifying a relative PRIORITY, a constant integral expression currently bounded between 101 and 65535 inclusive. Lower numbers indicate a higher priority.

没有任何迹象表明这适用于图书馆，图书馆。我希望静态库（libxyz.a）在这方面与单个对象文件一样工作，因为它们只是对象文件的集合，文档的措辞表明它在翻译单元（即不同的对象文件）。

Nowhere is there any indication of how this applies with respect to libraries, especially shared libraries. I would expect static libraries (libxyz.a) to work the same as individual object files in this respect, since they are just a collection of object files, and the wording of the documentation suggests that it works across translation units (i.e. with different object files).

然而，共享库本身就是有效的可执行文件---在给定的共享库中，初始化按照指定的顺序完成，但共享库作为整体以动态加载器指定的顺序初始化，即liba.so根据加载器的排序标准在libb.so之前或之后加载，并且init_priority属性不会影响该顺序。

However, shared libraries are effectively executables in their own right --- within a given shared library the initialization is done in the specified order, but shared libraries are initialized as a whole in the order specified by the dynamic loader i.e. liba.so is loaded either before or after libb.so based on the ordering criteria of the loader, and the init_priority attribute cannot affect that ordering.

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