glibc什么时候会发生文件流锁定？
通过阅读 glibc 文档，我最近了解到调用 getc 可能必须等待获取锁才能读取文件。我想验证在使用缓冲时，仅当需要读取实际文件以补充缓冲区时才获取锁。
谢谢！
Reading the glibc documentation, I recently learned that calls to getc may have to wait to acquire a lock to read a file. I wanted to verify that when using buffering a lock is only acquired when the actual file needs to be read to replenish the buffer.
Thanks!
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getc 调用的锁提供 stdio FILE 对象的应用程序级锁定，以允许同一应用程序中的多个线程对同一 FILE 对象进行线程安全访问。因此，每次读取字符时都需要获取它，而不仅仅是在填充缓冲区时获取。
但是，如果您不从多个线程访问 FILE，则永远不必等待锁定。如果获取/释放锁的开销太大（衡量这一点；不要只是假设），您还可以选择使用
flockfile和funlockfile手动锁定/解锁>，然后使用getc_unlocked。The lock invoked by
getcprovides application-level locking of the stdio FILE object, to allow thread-safe access to the same FILE object by multiple threads in the same application. As such, it will need to be acquired every time a character is read, not just when the buffer is replenished.But, if you aren't accessing the FILE from multiple threads, you'll never have to wait for the lock. If the overhead of acquiring/releasing the lock is too much (measure this; don't just assume), you also have the option of manually locking/unlocking using
flockfileandfunlockfile, then usinggetc_unlocked.