限制 Linux 静态库中的符号 [英] Restricting symbols in a Linux static library

问题描述

我正在寻找方法来限制导出到 Linux 静态库(存档)的 C 符号的数量.我想将这些限制为仅属于库官方 API 的那些符号.我已经使用静态"将大多数函数声明为静态，但这将它们限制在文件范围内.我正在寻找一种方法来限制图书馆的范围.

I'm looking for ways to restrict the number of C symbols exported to a Linux static library (archive). I'd like to limit these to only those symbols that are part of the official API for the library. I already use 'static' to declare most functions as static, but this restricts them to file scope. I'm looking for a way to restrict to scope to the library.

我可以使用 Ulrich Drepper 的 如何编写共享库，但我无法将这些技术应用于静态档案.在他早期的图书馆设计的良好实践论文中，他写道:

I can do this for shared libraries using the techniques in Ulrich Drepper's How to Write Shared Libraries, but I can't apply these techniques to static archives. In his earlier Good Practices in Library Design paper, he writes:

唯一的可能是组合所有需要的目标文件使用ld -r"将某些内部资源合二为一，然后限制符号由这个组合的目标文件导出.GNU 链接器可以选择这样做.

The only possibility is to combine all object files which need certain internal resources into one using 'ld -r' and then restrict the symbols which are exported by this combined object file. The GNU linker has options to do just this.

谁能帮我发现这些选项可能是什么?我在使用 'strip -w -K prefix_*' 方面取得了一些成功，但这感觉很粗鲁.理想情况下，我想要一个适用于 GCC 3 和 4 的解决方案.

Could anyone help me discover what these options might be? I've had some success with 'strip -w -K prefix_*', but this feels brutish. Ideally, I'd like a solution that will work with both GCC 3 and 4.

谢谢！

推荐答案

我不相信 GNU ld 有任何这样的选择；Ulrich 一定是指 objcopy，它有很多这样的选项:--localize-hidden、--localize-symbol=symbolname、--localize-symbols=filename.

I don't believe GNU ld has any such options; Ulrich must have meant objcopy, which has many such options: --localize-hidden, --localize-symbol=symbolname, --localize-symbols=filename.

--localize-hidden 特别允许人们对暴露的符号进行非常精细的控制.考虑:

The --localize-hidden in particular allows one to have a very fine control over which symbols are exposed. Consider:

int foo() { return 42; }
int __attribute__((visibility("hidden"))) bar() { return 24; }

gcc -c foo.c
nm foo.o
000000000000000b T bar
0000000000000000 T foo

objcopy --localize-hidden foo.o bar.o
nm bar.o
000000000000000b t bar
0000000000000000 T foo

所以 bar() 不再从对象导出(即使它仍然存在并且可用于调试).您还可以将 bar() 与 objcopy --strip-unneeded 一起删除.

So bar() is no longer exported from the object (even though it is still present and usable for debugging). You could also remove bar() all together with objcopy --strip-unneeded.

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