[SOLVED] Question about how to use shared library

[leileicats]

Hi, everyone. I meet some problems about how to use the shared libraries of Intel Threading Build Block.

I need use the shared library called libtbb.so. so my command line as follows:


g++ tbb.cxx -o tbb -L../lib -ltbb

After compilation, I get thetbb executable file.

However, I key in $./tbb, then it shows the eorror:

./tbb: error while loading shared libraries: libtbb.so: cannot open shared object file: No such file or directory

But the libtbb.so is in the directory ../lib. Does it mean I need explicitly give the path of shared library when I execute it? Should the path information be included during compilation?

thanks.

[lnostdal]

the runtime linker will only look in certain predefined places/directories for libraries (.so files)

you can however force it to load a specific library by using LD_PRELOAD



LD_PRELOAD=../libtdd.so ./tbb

[PaulFr]

IMHO, two solution are better than LD_PRELOAD:

1. Add the linker flag -rpath <path_to_library_directory>. So in your example, assuming your libraries will be installed in the parent directory ../lib, you would add the flag -Xlinker -rpath -Xlinker ../lib to your compilation
g++ tbb.cxx -o tbb -Xlinker -rpath -Xlinker ../lib -L../lib -ltbbSee the manual page for g++ for details about -Xlinker flag.

2. Set the environment variable LD_LIBRARY_PATH to refer to a set of directories which need to be searched. So for your example, you would set
$ export LD_LIBRARY_PATH=../lib:${LD_LIBRARY_PATH}.

In general, to figure out which libraries are picked up (or missing) you can use
ldd <binary>.

[leileicats]

Thank you very much for your replies.

I have another easy solution which also works on me. I just copy the shared library libtbb.so into the directory /usr/lib .