c - __func 函数的约定是什么？

Question

我在 Linux 代码中看到了一堆名为 __foo 的函数。双下划线代表什么，应该在什么时候使用？

Answer 1

这意味着它是一个保留标识符。 C++ 03和C99标准都提到了这一点。

C99:

7.1.3 Reserved identifiers

• All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use.
• All identifiers that begin with an underscore are always reserved for use as identifiers with file scope in both the ordinary and tag name spaces.

C++ 03:

Each name that contains a double underscore (_ _) or begins with an underscore followed by an uppercase letter (2.11) is reserved to the implementation for any use.

您还可以引用:

• What are the rules about using an underscore in a C++ identifier?
• What does a double underscore mean in a variable name in the C language?
• Why do people use __(double underscore) so much in C++