动态库编译时（引用静态库）could not read symbols: Bad value

最新推荐文章于 2021-05-15 13:35:58 发布

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最新推荐文章于 2021-05-15 13:35:58 发布

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分类专栏：重构C/C++

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在编译动态库时遇到`relocation R_X86_64_32 against 'a local symbol'`错误，提示需要使用`-fPIC`参数。问题可能源于编译.o文件或静态库时未添加此参数。解决方案是确保所有编译过程都包含`-fPIC`，以创建符合要求的动态库。

编译动态库时遇到relocation R_X86_64_32 against `a local symbol'的错误

编译动态库时遇到如下错误：

... relocation R_X86_64_32 against `a local symbol' can not be used when making a shared object; recompile with -fPIC

... could not read symbols: Bad value

解决办法编译器已经提示了：recompile with -fPIC

但是我们应该重新编译谁带上这个参数呢？经过我几番折腾，发现如下情况：

1、编译.o文件的时候，没有加参数-fPIC，这问题个在gcc version 3.4.6版本没有发生，可能那个编译器默认都给加上吧。

2、当前程序中有用到某个静态库，那个静态库编译.o文件的时候没有加上-fPIC（静态库其实就是.o文件打包）。补充一点：我发现手写Makefile时即使不加-fPIC也没有这个问题，这一点很郁闷，这个只在用automake工具编译出.a文件时才出现过。

知道原因了，解决办法自然有了，保证你编译.o文件的时候，都加上-fPIC，这样你才能编译出动态库来。

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I'm Trying to Link a static Library to a shared library , I'm Getting the Following error

/usr/bin/ld: ../../../libraries/log4cplus/liblog4cplus.a(fileappender.o): relocation R_X86_64_32S against `a local symbol' can not be used when making a shared object; recompile with -fPIC
../../../libraries/log4cplus/liblog4cplus.a: could not read symbols: Bad value
collect2: ld returned 1 exit status

Assuming you are generating a shared library, most probably what happens is that the variant of liblog4cplus.a you are using wasn't compiled with -fPIC. In linux, you can confirm this by extracting the object files from the static library and checking their relocations:

ar -x liblog4cplus.a  
readelf --relocs fileappender.o | egrep '(GOT|PLT|JU?MP_SLOT)'

If the output is empty, then the static library is not PIC and cannot be used to generate a shared object.

Since the static library contains object code which was already compiled, providing the -fPIC flag won't help.

You need to get ahold of a version of liblog4cplus.a compiled with -fPIC and use that one instead.