What's the difference between writing:
g++ test.cc -L/my/dir/ -lname
and
g++ test.cc /my/dir/libname.so ?
Are both correct?
The things that I can think of:
First one is cross platform, g++ from MINGW will look for DLL's
In the second one we explicitly specify we want dynamic linking
The difference is that
g++ test.cc -L/my/dir/ -lname
may succeed even if /my/dir/libname.so does not exist:
It can find libname.so from a system library directory (usually /lib, /usr/lib).
It can find libname.a, and do static linking.
Furthermore, it allows you to link to multiple libraries from the same directory without repeating the parent directory.
The first method looks into /my/dir directory for the library file at link time. However only a short library name libname.so (or whatever it finds according to OS) is written into the image. When the program starts, it will look for the library in some library path, i.e. LD_LIBRARY_PATH on linux. Now you can relocate the executable and the library into different new places and set a correct search path after relocation.
The second method writes the full path of the library into the image: /my/dir/libname.so. When the program starts, it will look for this particular path to get the library. This makes the image non-relocatable, unless the same library path exists in the new environment. The effect is similar to the '-rpath' method.
Related
There is a laptop on which I have no root privilege.
onto the machine I have a library installed using configure --prefix=$HOME/.usr .
after that, I got these files in ~/.usr/lib :
libXX.so.16.0.0
libXX.so.16
libXX.so
libXX.la
libXX.a
when I compile a program that invokes one of function provided by the library with this command :
gcc XXX.c -o xxx.out -L$HOME/.usr/lib -lXX
xxx.out was generated without warning, but when I run it error like this was thrown:
./xxx.out: error while loading shared libraries: libXX.so.16: cannot open shared object file: No such file or directory , though libXX.so.16 resides there.
my clue-less assumption is that ~/.usr/lib wasn't searched when xxx.out is invoked.
but what can I do to specify path of .so , in order that xxx.out can look there for .so file?
An addition is when I feed -static to gcc, another error happens like this:
undefined reference to `function_proviced_by_the_very_librar'
It seems .so does not matter even though -L and -l are given to gcc.
what should I do to build a usable exe with that library?
For other people who has the same question as I did
I found a useful article at tldp about this.
It introduces static/shared/dynamic loaded library, as well as some example code to use them.
There are two ways to achieve that:
Use -rpath linker option:
gcc XXX.c -o xxx.out -L$HOME/.usr/lib -lXX -Wl,-rpath=/home/user/.usr/lib
Use LD_LIBRARY_PATH environment variable - put this line in your ~/.bashrc file:
export LD_LIBRARY_PATH=/home/user/.usr/lib
This will work even for a pre-generated binaries, so you can for example download some packages from the debian.org, unpack the binaries and shared libraries into your home directory, and launch them without recompiling.
For a quick test, you can also do (in bash at least):
LD_LIBRARY_PATH=/home/user/.usr/lib ./xxx.out
which has the advantage of not changing your library path for everything else.
Should it be LIBRARY_PATH instead of LD_LIBRARY_PATH.
gcc checks for LIBRARY_PATH which can be seen with -v option
I am trying to write a simple application with GLFW on Linux. Right now the main file (the only file) is basically just a few lines of code to make sure the dynamic library linked correctly. Here it is:
#include <GLFW/glfw3.h>
#include <iostream>
int main()
{
glfwInit();
std::cout << "It works this far!" << std::endl;
glfwTerminate();
}
The include files are stored in a directory labelled "include" and the library files are stored in a directory labelled "lib". As of right now, I am compiling the program with the following line:
g++ -Wl,-Rlib -Iinclude -Llib test.cpp -o test -lglfw.3.2
It compiles and links just fine, but when I try to execute it, I get the following error:
./test: error while loading shared libraries: libglfw.so.3: cannot open shared object file: No such file or directory
Now, before you rush to downvote this question into oblivion and mark it as a duplicate, at least allow me to explain why I believe my question is different enough to not be a duplicate. I already attempted the solutions that the other questions presented, but it was unsuccessful. As you can see, I tried setting the path to the library during linking with the -Wl,-Rlib tag. I also tried setting LD_LIBRARY_PATH to point to the location of my libraries (the 'lib' folder), but it still threw the same error. (It didn't matter if the path was relative or absolute.)
So, the next thing I tried was running the ldd command on the executable. I got some other dependencies that were working just fine, but importantly, I got this:
libglfw.so.3 => not found
For some reason, it insists on looking for libglfw.so.3. It will not have it any other way. Upon renaming the library from libglfw.3.2.so to libglfw.so.3, the program executed just fine and printed It works this far! as if there were no problems at all.
Why would this happen?
For some reason, it insists on looking for libglfw.so.3. ... Upon renaming the library from libglfw.3.2.so to libglfw.so.3 ...
The ELF executables contain the exact name of the dynamic libraries used.
If the executable contains the library name "libglfw.so.3" the file must be named exactly like this.
The file naming scheme is intentionally done in a way that not the "full" version is coded into the file name: This way a later version ("libglfw.so.3.15") will work with the executable.
Normally there should be a symbolic link to the latest version of the library installed:
libglfw.so.3 -> libglfw.so.3.2
This symbolic link seems to be missing on your computer. I would say that this is an installation problem!
EDIT
The question could be: Why is the file name stored in the executable file not libglfw.3.2.so but libglfw.so.3?
The answer has to do with the backward compatibility when a new version of a library is installed:
Normally you would use the switch -lglfw and a symbolic link named libglfw.so is looked up.
If you stored the file name libglfw.so in the executable file and a new, incompatible version if this library (libglfw.so.4) is installed you would have no chance to get the program running by having both versions of the library installed.
To enable backward compatibility by having both versions of the library installed the "real" symbolic link name of the library (libglfw.so.3) must be stored in the executable file.
Therefore the "expected" file name of a library is stored in the library itself: Inside the file libglfw.so.3.2 you'll find some information that the file expects itself to be stored as libglfw.so.3.
The linker will use this information about the file name because it assumes that the library name given in the linker switch (-lglfw) is less "precise" than the name stored in the library itself.
For some reason, it insists on looking for libglfw.so.3. It will not have it any other way.
This is the Linux convention for shared libraries which is described here among other places. For Linux libfoo.so.x.y.z is considered to have the same ABI as libfoo.so.x. Usually when shared libraries are installed (e.g. via rpm, dpkg, etc.) there's an invocation of ldconfig that happens so that the just installed libraries have a symlink following the convention installed that references the library. Also these libs (if installed to a "trusted location"), are added to a linker cache for performance reasons.
It compiles and links just fine, but when I try to execute it, I get the following error:
./test: error while loading shared libraries: libglfw.so.3: cannot open shared object file: No such file or directory
libglfw.so.3 isn't on ld-linux.so's path.
As you can see, I tried setting the path to the library during linking with the -Wl,-Rlib
Still won't find it -- libglfw.so.3 isn't on ld-linux.so's path. You can add it by doing something like:
ldconfig -n /path/to/lib
Which should output the requisite libglfw.so.3 symlink for your lib.
IIRC setting the rpath might require a full path.
I also tried setting LD_LIBRARY_PATH to point to the location of my libraries
Again, libglfw.so.3 isn't on ld-linux.so's path.
I have a few related questions about my issues with compilation for embedded system. My questions are not only about HOW to do something, but more about WHY, because I have solutions for my problems (but maybe there are better ones?), but have no idea why some things works in some conditions, and does not work in others. I already spent some time with this, but until yesterday I was doing things a little blindly, with trials and errors, and without knowing what I was doing. Time to stop that! Please, help.
Scenario
I want to develop an application for Xilinx’s Zynq ARM processor, on Zedboard. The app will involve multithreading, some audio manipulation, and httpserver. So I will need pthread, alsa, sndfile and microhttpd libraries. I created rootfs with yocto. In original conf.local file I added/modified these lines:
BB_NUMBER_THREADS ?= "${#oe.utils.cpu_count()}"
PARALLEL_MAKE ?= "-j ${#oe.utils.cpu_count()}"
MACHINE ?= "zedboard-zynq7"
PACKAGE_CLASSES ?= "package_deb"
EXTRA_IMAGE_FEATURES = "debug-tweaks eclipse-debug"
IMAGE_INSTALL_append = "libgcc alsa-utils mpg123 libstdc++ sthttpd libmicrohttpd libsndfile1"
LICENSE_FLAGS_WHITELIST = "commercial_mpg123"
I also had to add some additional layers to bblayers.conf (and of course downloaded them):
meta-xilinx
meta-multimedia (from meta-openembedded)
meta-oe (from meta-openembedded)
meta-webserver (from meta-openembedded)
Lastly, I generated core-image-minimal with bitbake.
This, together with Linux kernel, and other stuff compiled separately, boots and works fine.
Problems
1. Simple app with this rootfs
It is app for Zynq, so I use XSDK, which is SDK from Xilinx, based on Eclipse. I created new Application project. In dialog window I chose Linux as platform, C++ as language, and I provided path to my unpacked rootfs (excactly the one that system boots with, via NFS). My rootfs path is /home/stas/ZedboardPetalinuxFS (it is not Petalinux, I just used to use it, and this folder name is still the same). This sets proper paths for library and headers search in rootfs.
I started with something very simple:
#include <pthread.h>
int main()
{
int i;
i = 1;
return 0;
}
I also added pthread library for linker (in Eclipse settings). Linking command at this point:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" -o "test.elf" ./src/main.o -lpthread
At this point it compiles. But it stops, when I add sndfile library
#include <sndfile.h>
This is reasonable, because this rootfs does not have all headers. I need to add another path for searching for headers. So I added path in yocto tmp folder, that has all the headers, that was needed for building rootfs. After I add it, it compiles again successfully. But problems started, when I added sndfile library for linking. Here is linking command and error:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" -o "test.elf" ./src/main.o -lpthread -lsndfile
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find -lsndfile
I looked to usr/lib to check if libsndfile.so is there, and I found only libsndfile.so.1 and ibsndfile.so.1.27. But it is also the case for pthread, and linker does not complain for that. I decided to create libsndfile.so by hand (I linked it to libsndfile.so.1). Linker stopped complaining about it, but started complaining about it’s dependencies. So I also creaded .so files for all the dependencies, and their dependencies, and added them for linking. Then it succeeded. At the end, linking command looked like this:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" -o "test.elf" ./src/main.o -lpthread -lvorbisenc -lvorbis -logg -lFLAC -lsndfile
So here goes the first question – why I did not needed .so file for pthread, but needed it for all other libraries? Or more general – when do I need .so file, and when .so.X file is enough?
2. Simple app - another approach
After the first try, I thought I should make another image, this time more suitable for development. Luckily, in Yocto it is quite easy – I just had to modify one line:
EXTRA_IMAGE_FEATURES = "debug-tweaks eclipse-debug dev-pkgs"
dev-pkgs option adds -dev packages for all installed packages.
So now I have rootfs with all needed headers, and .so files pointing where they should.
Before compilation, I removed unnecessary Include path, leaving only the one from rootfs, and removed all the libraries, except pthread, and sndfile. But then I get new errors:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" -o "test.elf" ./src/main.o -lsndfile -lpthread
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find /lib/libpthread.so.0
makefile:48: polecenia dla obiektu 'test.elf' nie powiodły się (commands for ‘test.elf’ did not succeed)
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find /usr/lib/libpthread_nonshared.a
I spotted, that it looks for libraries in my root folder. Quick search in Google (and SO:)) told me that I should set –-sysroot variable. So I added it to Eclipse option (in Miscelenious card in Linker options) like that:
--sysroot=/home/stas/ZedboardPetalinuxFS
So now linker command looked like this:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" --sysroot=/home/stas/ZedboardPetalinuxFS -o "test.elf" ./src/main.o -lsndfile -lpthread
And all succeed! I also wrote simple example that uses pthreads, and sndfile, and it also worked. But WHY? This leads me to second question:
Why do I need --sysroot option in this case? When do I need to use this option in general? And why this time I didn't have to add all the dependencies to linking command?
3. Another idea
At this point, I had an idea, to check what will happen, if I add --sysroot option having rootfs populated with old, non development image. But this gave me new errors:
arm-linux-gnueabihf-g++ -L"/home/stas/ZedboardPetalinuxFS/usr/lib" -L"/home/stas/ZedboardPetalinuxFS/lib" --sysroot=/home/stas/ZedboardPetalinuxFS -o "test.elf" ./src/main.o -lpthread -lvorbisenc -lvorbis -logg -lFLAC -lsndfile
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find crt1.o: No such file or directory
makefile:48: polecenia dla obiektu 'test.elf' nie powiodły się
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find crti.o: No such file or directory
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find -lpthread
/opt/Xilinx/SDK/2016.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabihf/5.2.1/../../../../arm-linux-gnueabihf/bin/ld: cannot find -lm
So third question – what does this errors mean?
Thanks very much in advance!
"why I did not needed .so file for pthread, but needed it for all
other libraries?"
Actually you do need pthread.so file. You included pthread.h but didn't link with -lpthread. So it's normal you don't see any linker errors.
"when do I need .so file, and when .so.X file is enough"
When you give "-lNAME" parameter to g++, the compiler tells the linker to find libNAME.so within library search paths. Since there may exist multiple versions of the same library(libNAME.so.1, libNAME.so.1.20), *.so files link to desired actual library file. (Versioning of shared objects, ld man pages)
"Why do I need --sysroot option in this case? When do I need to use this option in general? And why this time I didn't have to add all the dependencies to linking command?"
The "dev-pkgs" in EXTRA_IMAGE_FEATURES changes your sysroot implicitly to let you link against the dev packages(yoctoproject image-features). That's why you need -sysroot option. You generally need this option when cross compiling to provide a root for standard search paths for headers and libraries. You didn't need it because you didn't have dev-pkgs image feature that changes your sysroot
"So third question – what does this errors mean?"
Even your the most basic hello world code gets linked with standard c library(if you didn't specify otherwise). libm.so, libpthread.so and crt1.o files are parts of libc library and come with libc dev package. So the linker can't see the standard library directories when it looks from your old sysroot
why I did not needed .so file for pthread, but needed it for all other libraries?
A cross compiler will normally come with a C Runtime (including pthread), typically in a directory that is part of the cross compiler installation.
The linker has built in search paths for libraries. These are in respect to the sysroot, which would by default be set to search the cross compiler's own included target C Runtime. If you added any -L options it would search those first and then move on to these pre-defined directories.
When you linked against pthread it would have found at least libpthread.a in the cross compiler's library directory.
Or more general – when do I need .so file, and when .so.X file is enough?
Shared libraries in Linux typically have a major and a minor version number. Libraries are ABI compatible between different minor versions with the same major version, but not between major versions. Sometimes there are three levels of versions but the principal is similar.
When installing libraries it is common to install the actual file with the full name, eg. libmy.so.1.2, then provide symlinks to libmy.so.1 and libmy.so.
If you are linking an application can work with any library version then you would just specify the name, eg. -lmy. In that case you would need symlinks from libmy.so to libmy.so.1.
If you required a specific version you would put -l:libmy.so.1. The ':' indicates a literal file name.
Linker scripts may affect things and may result in specific versions being selected even when you do specify the short name.
Why do I need --sysroot option in this case? When do I need to use
this option in general?
What --sysroot does is prepend the given path onto all the search directories which would normally be used to search for includes and libraries. It is most useful when cross compiling (as you are doing now) to get the compiler and the linker to search inside the target root instead of the build host's own root.
If you have specified a sysroot you probably do not need to specify include paths via -I or linker paths via -L, assuming that the files are within their normal spots inside your target root.
And why this time I didn't have to add all the dependencies to linking command?
One possible scenario is that the first time, sndfile for statically rather than dynamically linked. This would happen if your first root image had only sndfile.a in the lib dir, or elsewhere on the search path. To then satisfy the requirements of sndfile.a you would also need to link the other libs.
When linking against sndfile.so the dependencies will automatically get loaded via the dynamic linking process.
That's just a working theory at present.
So third question – what does this errors mean?
They mean it cannot find even the C runtime library to link.
As described for the first question, it was previously finding the C runtime in the pre-defined search path (relative to the predefined sysroot) which located the C runtime supplied by the cross compiler.
You disturbed this by supplying your own sysroot. It was now only searching the target root. Since this target root filesystem did not have development libs installed, there was no C runtime there to find.
You are doing several things wrong:
looks like you are not using environment variables, but calling cross-compiler directly. So, instead of compiling with arm-linux-gnueabihf-g++ ..., you should do $CXX .... The CXX is the environment variable set by the yocto script to set environment for cross compilation. Using CXX, you do not need to manually pass --sysroot
You should not link directly to pthread library with -lpthread. You should use -pthread
I am trying to compile one of the projects found here
USB-I2C/SPI/GPIO Interface Adapter.
I downloaded the i2c_bridge-0.0.1-rc2.tgz package. I installed libusb and that seemed to go well with no issues. I go into the i2c_bridge-0.0.1-rc2/ directory and make. That compiles. I move into the i2c_bridge-0.0.1-rc2/i2c folder and make. It compiles and gives me ./i2c. However, when I run it, it says error while loading shared libraries: libi2cbrdg.so: cannot open shared object file: No such file or directory
The makefile in i2c_bridge-0.0.1-rc2/i2c has the library directory as ../. The libi2cbrdg.so is in this directory (i2c_bridge-0.0.1-rc2). I also copied the file to /usr/local/lib. An ls of the i2c_bridge-0.0.1-rc2/ directory is
i2c i2cbrdg.d i2cbrdg.o libi2cbrdg.a Makefile tests
i2cbrdg.c i2cbrdg.h INSTALL libi2cbrdg.so README u2c4all.sh
(That i2c is a directory)
If I sudo ./i2c, it still gives me the problem.
I had to take away the -Werror and -noWdecrepated (spelling?) options in all the makefiles to get them to compile, but that shouldn't affect this should it?
What else is necessary for it to find the .so file? If anyone can help me find out what is wrong I would be very grateful. If more information is needed I can post it.
You have to distinguish between finding so's at compile-time and at run-time. The -L flag you give at compile-time has nothing to do with localizing the library at run-time. This is rather done via a number of variables and some paths embedded in the library.
The best hot-fix for this problem is often setting LD_LIBRARY_PATH to the directory with the .so file, e.g.:
$ LD_LIBRARY_PATH=.. ./i2c
For a long-term solution, you need to either have a close look at the whole LD system with rpath and runpath, or use libtool (which solves these issues for your portably).
Copying a file to /usr/local/lib is often insufficient because ld caches the available libraries, so you need to re-run ldconfig (as root) after you copied a library to /usr/local/lib.
If you are building the code from source that needs the the library, you can put the path that the library is in in the environment variable LD_RUN_PATH before building, and the linker will save that path into the binary, so that it will automatically be looked for in the right place at runtime.
Linux specific: Alternately, put the library in /lib, /usr/lib, or some other path referenced in your /etc/ld.so.conf or its imported config fragments, and then all you need to do is run /sbin/ldconfig to refresh ld.so (the dynamic linker)'s cache of libraries.
This works for my issue,hope will help anyone.
gcc test.c -Wl,-rpath /usr/local/lib -lfcgi -o test.fcg
And -Wl,-rpath option is the key trick.
I am building a C++ application that uses Intel's IPP library. This library is installed by default in /opt and requires you to set LD_LIBRARY_PATH both for compiling and for running your software (if you choose the shared library linking, which I did). I already modified my configure.ac/Makefile.am so that I do not need to set that variable when compiling, but I still can't find the shared library at run-time; how do I do that?
I'm compiling with the -Wl, -R/path/to/libdir flag using g++
Update 1:
Actually my binary program has some IPP libraries correctly linked, but just one is not:
$ ldd myprogram
linux-vdso.so.1 => (0x00007fffa93ff000)
libippacem64t.so.6.0 => /opt/intel/ipp/6.0.2.076/em64t/sharedlib/libippacem64t.so.6.0 (0x00007f22c2fa3000)
libippsem64t.so.6.0 => /opt/intel/ipp/6.0.2.076/em64t/sharedlib/libippsem64t.so.6.0 (0x00007f22c2d20000)
libippcoreem64t.so.6.0 => /opt/intel/ipp/6.0.2.076/em64t/sharedlib/libippcoreem64t.so.6.0 (0x00007f22c2c14000)
[...]
libiomp5.so => not found
libiomp5.so => not found
libiomp5.so => not found
Of course the library is there:
$ locate libiomp5.so
/opt/intel/ipp/6.0.2.076/em64t/sharedlib/libiomp5.so
By /path/to/lib do you mean path to the directory containing the library, or the path to the actual file?
The -R option given a directory argument is treated like -rpath by ld, which is the option you're actually wanting here. It adds the given directory to the runtime library search path. That should work, as long as you give it the directory and not filename. I'm fairly confident about that, having done it myself, and because it's one of the hints given by libtool:
Libraries have been installed in:
/path/to/library-directory
If you ever happen to want to link against installed libraries
in a given directory, LIBDIR, you must either use libtool, and
specify the full pathname of the library, or use the `-LLIBDIR'
flag during linking and do at least one of the following:
add LIBDIR to the `LD_LIBRARY_PATH' environment variable
during execution
add LIBDIR to the `LD_RUN_PATH' environment variable
during linking
use the `-Wl,-rpath -Wl,LIBDIR' linker flag
have your system administrator add LIBDIR to `/etc/ld.so.conf'
(I paste this here since conceivably one of the other options could be more desirable - for example LD_RUN_PATH can save you makefile modification)
As suggested by Richard Pennington, the missing library is not used directly by my application, but it is used by the shared libraries I use. Since I cannot recompile IPP, the solution to my problem is to add -liomp5 when compiling, using the -R option for the linker. This actually adds the rpath for libiomp5.so fixing the problem!
You can check if the path to the library is being picked up from your -R flag by running the ldd command or the readelf command on your binary. The LD_LIBRARY_PATH environment variable is an override, so shouldn't be necessary normally.
You should use the -R option if possible.
If not, rename your executable and create a launch script that runs your executable, and in there set LD_LIBRARY_PATH just for that scope.
Depending on platform, you can modify ld.so.conf via /etc/ld.so.conf.d (Redhat/Fedora come to mind) which makes deploying changes to ld.so "easier" from a deployment scenario.
Besides all the useful hints posted here.. you're not trying to use a 64-bit specific library on a 32-bit system (or viceversa, depending on other conditions), are you?
bash:
export LD_LIBRARY_PATH=/path/to/lib
tcsh:
setenv LD_LIBRARY_PATH /path/to/lib
Try configuring your ldconfig through ld.so.conf so it searches your /opt/... directory by default.