不使用 libc 编译 [英] Compiling without libc

问题描述

我想在没有 (g)libc 的情况下编译我的 C 代码.如何停用它以及哪些功能依赖于它?

I want to compile my C-code without the (g)libc. How can I deactivate it and which functions depend on it?

我试过 -nostdlib 但它没有帮助:代码是可编译和运行的，但我仍然可以在我的可执行文件的十六进制转储中找到 libc 的名称.

I tried -nostdlib but it doesn't help: The code is compilable and runs, but I can still find the name of the libc in the hexdump of my executable.

推荐答案

如果你用 -nostdlib 编译你的代码，你将无法调用任何 C 库函数(当然)，但你也没有得到常规的 C 引导代码.特别是，Linux 上程序的真正入口点不是 main()，而是一个名为 _start() 的函数.标准库通常提供一个版本，它运行一些初始化代码，然后调用 main().

If you compile your code with -nostdlib, you won't be able to call any C library functions (of course), but you also don't get the regular C bootstrap code. In particular, the real entry point of a program on Linux is not main(), but rather a function called _start(). The standard libraries normally provide a version of this that runs some initialization code, then calls main().

尝试用 gcc -nostdlib -m32 编译:

void _start() {

    /* main body of program: call main(), etc */

    /* exit system call */
    asm("movl $1,%eax;"
        "xorl %ebx,%ebx;"
        "int  $0x80"
    );
}

_start() 函数应始终以调用 exit(或其他非返回系统调用，例如 exec)结束.由于通常的 exit() 不可用，上面的示例直接使用内联汇编调用系统调用.

The _start() function should always end with a call to exit (or other non-returning system call such as exec). The above example invokes the system call directly with inline assembly since the usual exit() is not available.

这篇关于不使用 libc 编译的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！