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I am attempting to install the protobuf library on a Redhat system (Amazon EC2's Linux build). I ran configure, make, and make install without a problem, and the .so libraries were copied over to /usr/local/lib. Since Redhat doesn't include the /usr/local/lib directory in /etc/ld.so.conf, I added it, and then ran ldconfig to update the linkages.

My problem is that, for whatever reason, ldconfig isn't picking up libprotobuf.so, even though it is in the /usr/local/lib directory.

Here is the output of ls -l /usr/local/lib:

total 61336
-rw-r--r-- 1 root root 17654940 Mar 26 02:39 libprotobuf.a
-rwxr-xr-x 1 root root      994 Mar 26 02:39 libprotobuf.la
-rw-r--r-- 1 root root  1948106 Mar 26 02:39 libprotobuf-lite.a
-rwxr-xr-x 1 root root     1029 Mar 26 02:39 libprotobuf-lite.la
lrwxrwxrwx 1 root root       25 Mar 26 02:39 libprotobuf-lite.so -> libprotobuf-lite.so.7.0.0
lrwxrwxrwx 1 root root       25 Mar 26 02:39 libprotobuf-lite.so.7 -> libprotobuf-lite.so.7.0.0
-rwxr-xr-x 1 root root   893083 Mar 26 02:39 libprotobuf-lite.so.7.0.0
lrwxrwxrwx 1 root root       20 Mar 26 02:39 libprotobuf.so -> libprotobuf.so.7.0.0
lrwxrwxrwx 1 root root       20 Mar 26 02:39 libprotobuf.so.7 -> libprotobuf.so.7.0.0
-rwxr-xr-x 1 root root  7326093 Mar 26 02:39 libprotobuf.so.7.0.0
-rw-r--r-- 1 root root 25883264 Mar 26 02:39 libprotoc.a
-rwxr-xr-x 1 root root     1010 Mar 26 02:39 libprotoc.la
lrwxrwxrwx 1 root root       18 Mar 26 02:39 libprotoc.so -> libprotoc.so.7.0.0
lrwxrwxrwx 1 root root       18 Mar 26 02:39 libprotoc.so.7 -> libprotoc.so.7.0.0
-rwxr-xr-x 1 root root  9071740 Mar 26 02:39 libprotoc.so.7.0.0
drwxr-xr-x 2 root root     4096 Mar 26 02:39 pkgconfig

Here is the output of ldconfig -v | grep protobuf:

libprotobuf.so.7 -> libprotobuf.so.7.0.0
libprotobuf-lite.so.7 -> libprotobuf-lite.so.7.0.0

What do I have to do to get libprotobuf recognized by the linker?

Edit: When I try to link the library directly, I get this error:

ldconfig: Ignored file /usr/local/lib/libprotobuf.so since it is not a regular file.

I tried copying libprotobuf.so.7.0.0 over libprotobuf.so so that it is no longer a symlink, which fixed the error, but my linker still can't find libprotobuf.

share|improve this question
up vote 1 down vote accepted

ld.so.conf is only used by the runtime dynamic linker. ld doesn't us that at all - you need to pass /usr/local/lib as a linker search directory (either directly to ld if you're calling it directly, or via your compiler).

For ld, GCC (or clang, and possibly quite a few other compilers), you do that with the -L flag.

share|improve this answer
You're right; I was barking up the wrong tree. My problem was as trivial as it gets -- I was passing -Llibprotobuf to GCC instead of -Lprotobuf. Thanks! – Kai Mar 27 '12 at 11:49

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