c - C 程序是否需要 main()？

Question

好吧，标题说明了一切。 main() 函数对于 C 程序来说是绝对必要的吗？

我问这个是因为我正在查看 Linux 内核代码，但没有看到 main() 函数。

Answer 1

不，ISO C 标准声明只有托管环境(例如具有底层操作系统的环境)才需要 main 函数。

对于像嵌入式系统(或操作系统本身)这样的独立环境，它是实现定义的。来自 C99 5.1.2:

Two execution environments are defined: freestanding and hosted. In both cases, program startup occurs when a designated C function is called by the execution environment.

In a freestanding environment (in which C program execution may take place without any benefit of an operating system), the name and type of the function called at program startup are implementation-defined.

至于Linux本身是如何启动的，Linux内核的启动点是start_kernel。不过，要更完整地了解整个引导过程，您应该开始 here .