c - C启动例程需要什么？

Question

引用其中一本 unix 编程书籍，

When a C program is executed by the kernelby, one of the exec functions calls special start-up routine. This function is called before the main function is called. The executable program file specifies this routine as the starting address for the program; this is set up by the link editor when it is invoked by the C compiler. This start-up routine takes values from the kernel the command-line arguments and the environment and sets things up so that the main function is called as shown earlier.

为什么我们需要一个中间人启动例程。 exec 函数可以直接调用 main 函数，内核可以直接将命令行参数和环境传递给 main 函数。为什么我们需要中间的启动例程？

Answer 1

因为C没有“插件”的概念。所以如果你想使用，比方说，malloc() 就必须有人初始化必要的数据结构。 C 程序员很懒，不想一直写这样的代码:

main() {
    initialize_malloc();
    initialize_stdio();
    initialize_...();
    initialize_...();
    initialize_...();
    initialize_...();
    initialize_...();

    ... oh wow, can we start already? ...
}

因此 C 编译器找出需要完成的工作，生成必要的代码并设置所有内容，以便您可以立即开始您的代码。