我如何用GCC声明一个绝对地址的变量？ [英] How can I declare a variable at an absolute address with GCC?

问题描述

我们正在研究链接器如何在我的一门课程中工作，其中一项任务是涉及 nm 命令的小练习。基本上我们只想匹配每个变量的类型和由 nm 打印的值。例如：

We are looking at how the linker works in one of my courses and one of the assignments is a little exercise involving the nm command. essentially we just want to match the type and the value printed by nm for each variable. for example:

char* B = NULL;

将给出地址（不相关），然后是B B.我已经成功完成了所有标签我们需要除了A.我已经读过，这只是意味着值是绝对的，不能被链接器改变。我尝试了很多涉及 volatile ， const ， static ，定义，以及其他任何我可以想到的尝试，但我目前没有想法。我曾在其他地方读过，这只能通过创建链接脚本才能实现，但事实并非如此，因为我的一些同行已经用C中的一行解决了这个问题。是否有人可以用C输出：

would give the address (irrelevant) then B B. I've done this successfully for all the labels we needed to except for A. I have read that this simply means the value is absolute and cannot be changed by the linker. I have experimented with many combinations involving volatile, const, static, define, and any thing else I could think to try, but I am presently out of ideas. I had read elsewhere that this could only be achieved by creating a linker script to do so, but that is not the case, as some of me peers have solved this with one line in C. Could any one come up with a way in C to output:

some address A A
...

对于它的目标文件调用 nm ？

Whem nm is called on it's object file?

推荐答案

在标准C中定义绝对符号有点棘手。但您可以使用非标准的内联汇编：

Defining absolute symbols in Standard C is a bit tricky. But you can use non-standard inline assembly:

$ cat x.c
asm (".globl A");
asm ("A = 0x42");
$ clang -c x.c
$ nm x.o
0000000000000042 A A

这篇关于我如何用GCC声明一个绝对地址的变量？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！