August 2021
Intermediate to advanced
450 pages
6h 57m
Chinese
Content preview from C++程序设计语言（第4部分：标准库）（原书第4版）
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30.4 错误处理
标准库包含的组件已有将近40年的开发历程。因此，它们处理错误的风格和方法并不统一：
·C风格库函数大多数通过设置errno来指示发生了错误；见13.1.2节和40.3节。
·很多对元素序列进行操作的算法返回一个尾后迭代器来指示“未找到”或“失败”；见33.1.1节。
·I/O流库要依赖于每个流中的一个状态来反映错误，并可能（根据用户需要）通过抛出异常来指示错误；见38.3节。
·一些标准库组件，如vector、string和bitset通过抛出异常来指示错误。
标准库的设计目标之一是所有组件都遵守“基本保证”（见13.2节）；即，即使抛出了异常，也不会有资源（如内存）泄漏，且不会有标准库类的不变式被破坏的情况出现。
30.4.1 异常
一些标准库组件通过抛出异常来报告错误：
任何直接或间接使用这些组件的代码都可能遇到这些异常。而且，对任何操作，如果它处理可能抛出异常的对象，那么我们必须假定这个操作也抛出此异常，除非已经小心地避免了这种情况的发生。例如，如果packaged_task要求执行的函数会抛出一个异常，那么packaged_task也会抛出一个异常。
除非你确认使用组件的方式不会令它们抛出异常，否则坚持在某处（如main（））捕获标准库异常类层次的某个根类（如exception）和任意异常（…）是一个很好的编程习惯。 ...
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