gcc共享库未能连接到glibc。

I'm writing a simple C shared library using Eclipse CDT under Linux 64bit.

我在Linux 64bit下使用Eclipse CDT编写一个简单的C共享库。

The code has one reference to the rand() function in the <stdlib.h> It compiles fine but when linking it reports the following error from the linker:

代码有一个对编译良好，但在链接时报告链接器的以下错误: 中的rand()函数的引用。h>

gcc -shared -o "libalg.so"  ./sort.o   
/usr/bin/ld: ./sort.o: relocation R_X86_64_PC32 against undefined symbol `rand@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value

sort.o is the object file compiled from the file. libalg.so is the target shared library name.

排序。o是从文件中编译的对象文件。libalg。目标共享库名称也是如此。

Can anyone explaining why this happen?

有人能解释一下为什么会这样吗?

Thanks.

谢谢。

1 个解决方案

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On x86_64 architecture gcc requires you to use -fPIC i.e Position Independent Code by default.

在x86_64体系结构上，gcc要求您使用-fPIC i。e位置独立的代码默认。

The underlying reason for the error is that the relocation type for the symbol rand is of type R_X86_64_PC32 which means that it is PC relative and should lie within 32bit offset from the following instruction.

出现错误的根本原因是符号rand的重新定位类型为R_X86_64_PC32，这意味着它是PC的亲戚，应该位于与以下指令的32位偏移量之间。

But the current architecture is of x86_64 type which means that it can lie anywhere within the 64bit address space.

但是当前的架构是x86_64类型，这意味着它可以位于64位地址空间中的任何位置。

So the dynamic linker actually can not link a symbol with such a relocation type.

因此动态链接器实际上不能将一个符号与这样的重定位类型连接。

Either you have to use -fPIC or compile your code using the -mcmodel=large which will actually make the relocation type to R_X86_64_64.

要么使用-fPIC，要么使用-mcmodel=large编译代码，这实际上会将重新定位类型设置为R_X86_64_64。

For more details on how linking is done refer to this great blog by Eli Bendersky

有关链接是如何完成的更多细节，请参考Eli Bendersky的这个伟大的博客

#1