ELF 可执行程序在运行阶段寻找动态库的路径顺序

Linux 上 ELF 格式的可执行程序，在程序启动阶段，会加载  ld.so 这个动态库（比较奇妙的是，它也可以直接被执行，动态库/可执行程序 二合一？），并通过它来加载其它需要的动态库。

ld.so  manual page 中介绍了运行阶段寻找动态库的顺序 ：

       ld.so  loads  the shared libraries needed by a program, prepares the program to run, and then runs it.  Unless explicitly

       specified via the -static option to ld during compilation, all Linux programs are incomplete and require further  linking

       at run time.

       The necessary shared libraries needed by the program are searched for in the following order

       o      Using  the  environment  variable  LD_LIBRARY_PATH  (LD_AOUT_LIBRARY_PATH for a.out programs).  Except if the executable is a setuid/setgid binary, in which case it is ignored.

       o      From the cache file /etc/ld.so.cache which contains a compiled list of candidate libraries previously found in the

              augmented library path.

       o      In the default path /usr/lib, and then /lib.

如果在链接阶段，通过 -static 选项指定了动态库搜索路径的话，那么这个路径会被优先选择