什么可能导致流进入“坏"?状态?

问题描述

在 C++ 中，每个流都有一个 bad 位:

In C++, each stream has a bad bit:

该标志由在读取或写入数据时发生错误时对流执行的操作设置，通常会导致流的完整性丢失.

来源

什么会导致流失去完整性"并进入 bad 状态?这与 fail 状态不同，当输入流尝试将值存储到不能接受该值的变量中时(例如尝试将字符串存储到整数变量中)，最常发生这种情况).

What would cause a stream to "lose integrity" and enter the bad state? This is not the same as the fail state, which most often occurs when an input stream attempts to store a value into a variable that cannot accept said value (such as attempting to store a string into an integer variable).

注意这个问题是c++文件坏位的更一般形式，即特定于文件输入流；这个问题不是一个完全重复的问题，因为它通常适用于输入和输出流.

Note that this question is a more general form of c++ file bad bit, which is specific to file input streams; this question is not an exact duplicate as it applies to both input and output streams in general.

推荐答案

根据 cppreference.com:

标准库在以下情况下设置badbit:

• 通过 put() 或 write() 插入输出流失败原因.

• Insertion into the output stream by put() or write() fails for any reason.

通过 operator<<、std::put_money 或std::put_time，无法完成，因为输出结束流已到达(构面的格式化输出函数，例如num_put::put() 或 money_put::put()，返回一个迭代器 iter，例如iter.failed()==true)

Insertion into the output stream by operator<<, std::put_money or std::put_time, could not complete because the end of the output stream was reached (The facet's formatting output function such as num_put::put() or money_put::put(), returns an iterator iter such that iter.failed()==true)

Stream 是用 rdbuf() 的空指针构造的，或者putback()/unget() 在带有空 rdbuf() 的流上调用，或者传递给operator<<(basic_streambuf*)

Stream is constructed with a null pointer for rdbuf(), or putback()/unget() is called on a stream with a null rdbuf(), or a null pointer passed to operator<<(basic_streambuf*)

rdbuf()->sputbackc() 或 rdbuf()->sungetc() 返回 traits::eof()到putback() 或unget()`

rdbuf()->sputbackc() or rdbuf()->sungetc() return traits::eof() to putback() orunget()`

rdbuf()->pubsync() 返回 -1 到 sync()，到 flush()，或到unitbuf 流上的 ostream::sentry 析构函数

rdbuf()->pubsync() returns -1 to sync(), to flush(), or to the destructor of ostream::sentry on a unitbuf stream

任何成员函数在 I/O 操作期间抛出异常关联的流缓冲区(例如 sbumpc()、xsputn()、sgetc()、overflow(), etc)

Exception is thrown during an I/O operation by any member function of the associated stream buffer (e.g. sbumpc(), xsputn(), sgetc(), overflow(), etc)

在iword() 或pword() 中抛出异常(例如std::bad_alloc)

Exception is thrown in iword() or pword() (e.g. std::bad_alloc)

这可能是选择 cppreference.com 而不是 www.cpluplus.com 的另一个原因，请参阅:cplusplus.com 有什么问题?

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