C程序共享的库链接不设置LD_LIBRARY_PATH [英] C program linking with shared library without setting LD_LIBRARY_PATH

问题描述

我在读介绍GCC和它说，如果一个包有两种.A和.so。 GCC preFER的共享库。默认情况下，加载共享库只能在$ P $搜索pdefined设置系统目录，如的/ usr / local / lib目录和的/ usr中/ lib目录。如果库不位于这些目录之一，必须将它添加到负载路径，或者你需要使用 -static 选项强制它使用.A库。不过，我试过如下：

I was reading Introduction to GCC and it says if a package has both .a and .so. gcc prefer the shared library. By default the loader searches for shared libraries only in a predefined set of system directories, such as /usr/local/lib and /usr/lib. If the library is not located in one of these directories it must be added to the load path, or you need to use -static option to force it to use the .a library. However, I tried the following:

VIM的hello.c：

vim hello.c:

#include <gmp.h>
#include <stdio.h>

int main() {
        mpz_t x;
        mpz_init(x);
        return 0;
}

gcc hello.c -I/opt/include -L/opt/lib -lgmp  (my gmp library is in opt)
./a.out

和它运行。书中说，它应该具备以下错误：

And it runs. The book says it should have the following error:

./a.out: error while loading shared libraries:
libgdbm.so.3: cannot open shared object file:
No such file or directory

（当然，书中使用GDBM为例但我用GMP，但是这没有关系吧？）

(well, the book uses GDBM as example but I used GMP, but this won't matter right?)

不过，我没有设置 LD_LIBRARY_PATH = /选择/ lib目录，并且你可以看到我没有使用 -static 选项要么，但的a.out 仍然运行。

However, I did not set LD_LIBRARY_PATH=/opt/lib, and as you can see I did not use -static option either, but a.out still runs.

你能都告诉我，为什么和告诉我怎么走在书中描述的错误？是的，我要的错误，所以我会明白我误解了。

Can you all tell me why and show me how to get the error described in the book? Yes I want the error so I will understand what I misunderstood.

推荐答案

从你的回应我的评论：

linux-gate.so.1 => (0xb7746000)
libgmp.so.10 => /usr/lib/i386-linux-gnu/libgmp.so.10 (0xb76c5000)
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7520000)
/lib/ld-linux.so.2 (0xb7747000) 

所以，你的程序是从 / usr / lib目录拿起库。

你能尝试做的是在你的的/ opt / lib中，并连接到新的名称重命名库。

What you can try to do is rename the lib in your /opt/lib, and link against the new name.

mv /opt/lib/libgmp.so /opt/lib/libgmp-test.so
gcc hello.c -I/opt/include -L/opt/lib -lgmp-test

然后尝试运行该程序。此外，比较 LDD 对结果的新的a.out 对你有什么了。

Then try running the program. Also, compare the result of ldd against the new a.out against what you got before.

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