当要编译的可执行程序依赖共享库时，linker按下面所示顺序查找其依赖的库。
下面的内容出自gcc manual，作为笔记，记录于此。
The linker uses the following search paths to locate required shared libraries.
1. Any directories specified by -rpath-link options.
2. Any directories specified by -rpath options.
The difference between -rpath and -rpath-link is that directories specified by -rpath options are included in the executable and used at runtime, whereas the -rpath-link option is only effective at link time. It is for the native linker only.
3. On an ELF system, if the -rpath and "rpath-link" options were not used, search the contents of the environment variable "LD_RUN_PATH". It is for the native linker only.
4. On SunOS, if the -rpath option was not used, search any directories specified using -L options.
5. For a native linker, the contents of the environment variable "LD_LIBRARY_PATH".
6. For a native ELF linker, the directories in "DT_RUNPATH" or "DT_RPATH" of a shared library are searched for shared libraries needed by it. The "DT_RPATH" entries are ignored if "DT_RUNPATH" entries exist.
7. The default directories, normally /lib and /usr/lib.
8. For a native linker on an ELF system, if the file /etc/ld.so.conf exists, the list of directories found in that file.
If the required shared library is not found, the linker will issue a warning and continue with the link.
可见，-rpath-link指定的查找路径只会被linker使用，而-rpath指定的查找路径除用于linker查找外，还会在进程启动时被loader作为共享库查找路径。
【参考资料】
1. -rpath in manual page of gcc: man gcc and find -rpath
======================= EOF ====================