How to link to my own library in gcc?

Question

Command to build executable:
g++ -I../include/redis -L../lib/redis redis.cpp -o redis -lhiredis

Description:
I have libhiredis.so in ../lib/redis/. And in /usr/local/lib/hiredis13/, there are libhiredis.so and libhiredis.so.0.13, this libhiredis.so is a symbol link to libhiredis.so.0.13.Then I ldd redis, here is the result:

linux-vdso.so.1 => (0x00007ffd227f7000) libhiredis.so.0.13 => not found libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00007f7ebca0d000) libm.so.6 => /lib64/libm.so.6 (0x00007f7ebc70b000) libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f7ebc4f5000) libc.so.6 => /lib64/libc.so.6 (0x00007f7ebc132000) /lib64/ld-linux-x86-64.so.2 (0x00007f7ebcd23000)

Gcc should link to libhiredis.so in ../lib/redis/, am I right?

@GundolfGundelfinger Thank you.I rename libhiredis.so to libhiredis.so.0.13 and make libhiredis.so a symbol link of libhiredis.so.0.13.Thant worked! :-) — CharlesLiuChina
– CharlesLiuChina, Commented Oct 25, 2016 at 7:44
DON'T RENAME -- create a symlink to the original. (or build with the proper name to begin with :) — David C. Rankin
– David C. Rankin, Commented Oct 25, 2016 at 7:58
@DavidC.Rankin The original is libhiredis.so which is not a symlink, so I rename it and create a symlink to it. — CharlesLiuChina
– CharlesLiuChina, Commented Oct 25, 2016 at 11:11

rodrigo · Accepted Answer · 2016-10-25 07:42:55Z

Probably your library has a SONAME (libhiredis.so.0.13) so the program records it instead of the name of the file. Then, in runtime, that SONAME is searched for in the usual directories.

Your library is in /usr/local/lib/hiredis13/, and that is not a usual directory. The solution is one of the following:

Add the /usr/local/lib/hiredis13 directory in /etc/ld.so.conf or /etc/ld.so.conf.d/* and re-run ldconfig.
Export the environment variable LD_LIBRARY_PATH=/usr/local/lib/hiredis13 when running the program.
Use the -rpath linker option.

The -rpath method is a good choice as it will embed the library path in the executable making it immune from updates/changes that reset or alter ld.so.conf or LD_LIBRARY_PATH
@DavidC.Rankin Agreed, I prefer LD_LIBRARY_PATH to others.
@DavidC.Rankin: Personally, I prefer the LD_LIBRARY_PATH and a shell script that exports it and launches the binary.

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