C语言引用链接脚本中定义的符号
1. 使用ld --verbose 查看当前编译器默认的链接脚本：
default.ld
/* GNU ld (GNU Binutils for Ubuntu) 2.26.1
Supported emulations:
elf_x86_64
elf32_x86_64
elf_i386
elf_iamcu
i386linux
elf_l1om
elf_k1om
i386pep
i386pe
using internal linker script: */
/* ================================================= */
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/* Copyright (C) 2014-2015 Free Software Foundation, Inc.
Copying and distribution of this script, with or without modification,
are permitted in any medium without royalty provided the copyright
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__bss_start_xxdk =.; --->>> 添加自定义符号 <<<---
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__bss_end_xxdk =.; --->>> 添加自定义符号 <<<---
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/*================================================== */
2. 在上述默认链接脚本中添加了两个自定义的符号:
__bss_start_xxdk =; --->>> 添加自定义符号, <<<---
__bss_end_xxdk =.; --->>> 添加自定义符号 <<<---
在符号表中创建项，__bss_start_xxdk, 其持有当前内存位置(地址)“.”，但是该内存位置中没有存放任何有效的值。也就是说，不能访问一个链接脚本中定义的符号的“值”，它没有有效值。只能使用链接脚本中定义符号的地址；
因此在源码中使用链接脚本定义的符号，应该使用该符号的地址，而不是试图访问该符号的地址中的值；
3. 源码中使用链接脚本中定义的符号:
#include - 编译: gcc elf.c -T default.ld 让链接器使用我们修改过的默认脚本
- 运行./a.out:
0
0x601038
0x601040
- 查看符号表: objdump -h a.out | grep xxdk
0000000000601040 g .bss 0000000000000000 __bss_end_xxdk
0000000000601038 g .bss 0000000000000000 __bss_start_xxdk