c++ - #include "xxx.h"与 #include <xxx.h> 的规则是什么？

Question

<分区>

Answer 1

根据 ISO 标准，规则很少。这两种形式在查找头文件的位置方面都依赖于实现。它们甚至不必是 文件。

第2.9除了可以包含 " 之外，C++11 对这两个变体没有区别。在<>变体和 >在""变体，但很少有人会愚蠢到在文件名中使用这些字符:-)

第16.2进一步说明:

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A preprocessing directive of the form # include < h-char-sequence> new-line searches a sequence of implementation-defined places for a header identified uniquely by the specified sequence between the < and > delimiters, and causes the replacement of that directive by the entire contents of the header. How the places are specified or the header identified is implementation-defined.

A preprocessing directive of the form # include " q-char-sequence" new-line causes the replacement of that directive by the entire contents of the source file identified by the specified sequence between the " delimiters. The named source file is searched for in an implementation-defined manner. If this search is not supported, or if the search fails, the directive is reprocessed as if it read # include < h-char-sequence> new-line with the identical contained sequence (including > characters, if any) from the original directive.

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我倾向于使用 <>用于系统标题和 ""对于我自己的标题，但这只是个人喜好。我会注意到上述 C++11 文档指出:

Note: Although an implementation may provide a mechanism for making arbitrary source files available to the <> search, in general programmers should use the <> form for headers provided with the implementation, and the "" form for sources outside the control of the implementation.

这不是强制性的，但它仍然是一个好主意。