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.
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$HOME/.usr/lib -lXX -Wl,-rpath=/home/user/.usr/lib
Use LD_LIBRARY_PATH environment variable - put this line in your ~/.bashrc file:
export LD_LIBRARY_PATH=/home/user/.usr/lib
This will work even for a pre-generated binaries, so you can for example download some packages from the debian.org, unpack the binaries and shared libraries into your home directory, and launch them without recompiling.
For a quick test, you can also do (in bash at least):
LD_LIBRARY_PATH=/home/user/.usr/lib ./xxx.out
which has the advantage of not changing your library path for everything else.
Should it be LIBRARY_PATH instead of LD_LIBRARY_PATH.
gcc checks for LIBRARY_PATH which can be seen with -v option
I have a few related questions about my issues with compilation for embedded system. My questions are not only about HOW to do something, but more about WHY, because I have solutions for my problems (but maybe there are better ones?), but have no idea why some things works in some conditions, and does not work in others. I already spent some time with this, but until yesterday I was doing things a little blindly, with trials and errors, and without knowing what I was doing. Time to stop that! Please, help.
Scenario
I want to develop an application for Xilinx’s Zynq ARM processor, on Zedboard. The app will involve multithreading, some audio manipulation, and httpserver. So I will need pthread, alsa, sndfile and microhttpd libraries. I created rootfs with yocto. In original conf.local file I added/modified these lines:
BB_NUMBER_THREADS ?= "${#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'm trying to compile my program and it returns this error :
usr/bin/ld: cannot find -l<nameOfTheLibrary>
in my makefile I use the command g++ and link to my library which is a symbolic link to my library located on an other directory.
Is there an option to add to make it work please?
To figure out what the linker is looking for, run it in verbose mode.
For example, I encountered this issue while trying to compile MySQL with ZLIB support. I was receiving an error like this during compilation:
/usr/bin/ld: cannot find -lzlib
I did some Googl'ing and kept coming across different issues of the same kind where people would say to make sure the .so file actually exists and if it doesn't, then create a symlink to the versioned file, for example, zlib.so.1.2.8. But, when I checked, zlib.so DID exist. So, I thought, surely that couldn't be the problem.
I came across another post on the Internets that suggested to run make with LD_DEBUG=all:
LD_DEBUG=all make
Although I got a TON of debugging output, it wasn't actually helpful. It added more confusion than anything else. So, I was about to give up.
Then, I had an epiphany. I thought to actually check the help text for the ld command:
ld --help
From that, I figured out how to run ld in verbose mode (imagine that):
ld -lzlib --verbose
This is the output I got:
==================================================
attempt to open /usr/x86_64-linux-gnu/lib64/libzlib.so failed
attempt to open /usr/x86_64-linux-gnu/lib64/libzlib.a failed
attempt to open /usr/local/lib64/libzlib.so failed
attempt to open /usr/local/lib64/libzlib.a failed
attempt to open /lib64/libzlib.so failed
attempt to open /lib64/libzlib.a failed
attempt to open /usr/lib64/libzlib.so failed
attempt to open /usr/lib64/libzlib.a failed
attempt to open /usr/x86_64-linux-gnu/lib/libzlib.so failed
attempt to open /usr/x86_64-linux-gnu/lib/libzlib.a failed
attempt to open /usr/local/lib/libzlib.so failed
attempt to open /usr/local/lib/libzlib.a failed
attempt to open /lib/libzlib.so failed
attempt to open /lib/libzlib.a failed
attempt to open /usr/lib/libzlib.so failed
attempt to open /usr/lib/libzlib.a failed
/usr/bin/ld.bfd.real: cannot find -lzlib
Ding, ding, ding...
So, to finally fix it so I could compile MySQL with my own version of ZLIB (rather than the bundled version):
sudo ln -s /usr/lib/libz.so.1.2.8 /usr/lib/libzlib.so
Voila!
If your library name is say libxyz.so and it is located on path say:
/home/user/myDir
then to link it to your program:
g++ -L/home/user/myDir -lxyz myprog.cpp -o myprog
There does not seem to be any answer which addresses the very common beginner problem of failing to install the required library in the first place.
On Debianish platforms, if libfoo is missing, you can frequently install it with something like
apt-get install libfoo-dev
The -dev version of the package is required for development work, even trivial development work such as compiling source code to link to the library.
The package name will sometimes require some decorations (libfoo0-dev? foo-dev without the lib prefix? etc), or you can simply use your distro's package search to find out precisely which packages provide a particular file.
(If there is more than one, you will need to find out what their differences are. Picking the coolest or the most popular is a common shortcut, but not an acceptable procedure for any serious development work.)
For other architectures (most notably RPM) similar procedures apply, though the details will be different.
Compile Time
When g++ says cannot find -l<nameOfTheLibrary>, it means that g++ looked for the file lib{nameOfTheLibrary}.so, but it couldn't find it in the shared library search path, which by default points to /usr/lib and /usr/local/lib and somewhere else maybe.
To resolve this problem, you should either provide the library file (lib{nameOfTheLibrary}.so) in those search paths or use -L command option. -L{path} tells the g++ (actually ld) to find library files in path {path} in addition to default paths.
Example: Assuming you have a library at /home/taylor/libswift.so, and you want to link your app to this library. In this case you should supply the g++ with the following options:
g++ main.cpp -o main -L/home/taylor -lswift
Note 1: -l option gets the library name without lib and .so at its beginning and end.
Note 2: In some cases, the library file name is followed by its version, for instance libswift.so.1.2. In these cases, g++ also cannot find the library file. A simple workaround to fix this is creating a symbolic link to libswift.so.1.2 called libswift.so.
Runtime
When you link your app to a shared library, it's required that library stays available whenever you run the app. In runtime your app (actually dynamic linker) looks for its libraries in LD_LIBRARY_PATH. It's an environment variable which stores a list of paths.
Example: In case of our libswift.so example, dynamic linker cannot find libswift.so in LD_LIBRARY_PATH (which points to default search paths). To fix the problem you should append that variable with the path libswift.so is in.
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/taylor
During compilation with g++ via make define LIBRARY_PATH if it may not be appropriate to change the Makefile with the -Loption. I had put my extra library in /opt/lib so I did:
$ export LIBRARY_PATH=/opt/lib/
and then ran make for successful compilation and linking.
To run the program with a shared library define:
$ export LD_LIBRARY_PATH=/opt/lib/
before executing the program.
First, you need to know the naming rule of lxxx:
/usr/bin/ld: cannot find -lc
/usr/bin/ld: cannot find -lltdl
/usr/bin/ld: cannot find -lXtst
lc means libc.so, lltdl means libltdl.so, lXtst means libXts.so.
So, it is lib + lib-name + .so
Once we know the name, we can use locate to find the path of this lxxx.so file.
$ locate libiconv.so
/home/user/anaconda3/lib/libiconv.so # <-- right here
/home/user/anaconda3/lib/libiconv.so.2
/home/user/anaconda3/lib/libiconv.so.2.5.1
/home/user/anaconda3/lib/preloadable_libiconv.so
/home/user/anaconda3/pkgs/libiconv-1.14-0/lib/libiconv.so
/home/user/anaconda3/pkgs/libiconv-1.14-0/lib/libiconv.so.2
/home/user/anaconda3/pkgs/libiconv-1.14-0/lib/libiconv.so.2.5.1
/home/user/anaconda3/pkgs/libiconv-1.14-0/lib/preloadable_libiconv.so
If you cannot find it, you need to install it by yum (I use CentOS). Usually you have this file, but it does not link to right place.
Link it to the right place, usually it is /lib64 or /usr/lib64
$ sudo ln -s /home/user/anaconda3/lib/libiconv.so /usr/lib64/
Done!
ref: https://i-pogo.blogspot.jp/2010/01/usrbinld-cannot-find-lxxx.html
When you compile your program you must supply the path to the library; in g++ use the -L option:
g++ myprogram.cc -o myprogram -lmylib -L/path/foo/bar
I had this problem with compiling LXC on a fresh VM with Centos 7.8. I tried all the above and failed. Some suggested removing the -static flag from the compiler configuration but I didn't want to change anything.
The only thing that helped was to install glibc-static and retry. Hope that helps someone.
Check the location of your library, for example lxxx.so:
locate lxxx.so
If it is not in the /usr/lib folder, type this:
sudo cp yourpath/lxxx.so /usr/lib
Done.
Apart from the answers already given, it may also be the case that the *.so file exists but is not named properly. Or it may be the case that *.so file exists but it is owned by another user / root.
Issue 1: Improper name
If you are linking the file as -l<nameOfLibrary>
then library file name MUST be of the form lib<nameOfLibrary>
If you only have <nameOfLibrary>.so file, rename it!
Issue 2: Wrong owner
To verify that this is not the problem - do
ls -l /path/to/.so/file
If the file is owned by root or another user, you need to do
sudo chown yourUserName:yourUserName /path/to/.so/file
Here is Ubuntu information of my laptop.
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic
I use locate to find the .so files for boost_filesystem and boost_system
locate libboost_filesystem
locate libboost_system
Then link .so files to /usr/lib and rename to .so
sudo ln -s /usr/lib/x86_64-linux-gnu/libboost_filesystem.so.1.65.1 /usr/lib/libboost_filesystem.so
sudo ln -s /usr/lib/x86_64-linux-gnu/libboost_system.so.1.65.1 /usr/lib/libboost_system.so
Done! R package velocyto.R was successfully installed!
This error may also be brought about if the symbolic link is to a dynamic library, .so, but for legacy reasons -static appears among the link flags. If so, try removing it.
The library I was trying to link to turned out to have a non-standard name (i.e. wasn't prefixed with 'lib'), so they recommended using a command like this to compile it -
gcc test.c -Iinclude lib/cspice.a -lm
I encountered the same error message.
I built the cmocka as a so and tried to link it to my executable.
But ld always complains below:
/usr/bin/ld: cannot find -lcmocka
It turns out that there are 3 files generated after cmocka is built:
libcmocka.so
libcmocka.so.0
libcmocka.so.0.7.0
1 and 2 are symbol links and only 3 is the real file.
I only copied the 1 to my library folder, where ld failed to find the 3.
After I copied all 3, ld works.
I need to build two 3rd party shared libraries, so their .so files will be reused by other projects. However, after build one of these libraries contains hardcoded path to another. This path is invalid on other machines and causes linker warnings. How can I prevent the full path from being embedded in the resulting .so files?
Details:
First library source: ~/dev/A
Second library source: ~/dev/B
Both of them have configure script to generate make files. Library B depends on A. So, first I build A:
$ ~/dev/A/configure --prefix=~/dev/A-install
$ make && make install
Then I build B:
$ ~/dev/B/configure --prefix=~/dev/B-install --with-A=~/dev/A-install
$ make && make install
Then I want to upload the contents of ~/dev/A-install and ~/dev/B-install to our file server, so other teams and build machines can use the binaries. But they get linker warnings when they try to use B:
/usr/bin/ld: warning: libA.so.2, needed by /.../deps/B/lib/libB.so, not found (try using -rpath or -rpath-link)
When I run ldd libB.so it gives:
...
libA.so.2 => /home/alex/dev/A-install/lib/libA.so.2
Obviously this path exists only on my machine and cannot be found on other machines.
How can I remove full hardcoded path from libB.so?
Thanks.
You have to use --prefix value that will be valid in the runtime environment for both packages!
Than you override prefix or DESTDIR (prefix replaces the prefix, DESTDIR is prepended to it, but works more reliably) on the make command-line when installing. Like:
~/dev/A$ ./configure
~/dev/A$ make
~/dev/A$ make install prefix=~/dev/A-install
~/dev/B$ ./configure --with-A=~/dev/A-install
~/dev/B$ make
~/dev/B$ make install prefix=~/dev/B-install
or (which is preferred and is how all package-building tools use it):
~/dev/A$ ./configure
~/dev/A$ make
~/dev/A$ make install DESTDIR=~/dev/A-install
~/dev/B$ ./configure --with-A=~/dev/A-install/usr/local
~/dev/B$ make
~/dev/B$ make install prefix=~/dev/B-install
because this way you are installing to ~/dev/A-install/$prefix, so with default prefix ~/dev/A-install/usr/local. The advantage of this later option is, that if you redefine some specific installation paths without refering to prefix (say --sysconfdir=/etc), DESTDIR will still get prepended to it, while it won't be affected by prefix.
-Wl,-rpath,~/deps/A/lib:~/deps/B/lib:~/dev/MyApp/bin
This linker option is responsible for saving the path inside the library. You need somehow to remove this.
See with ./configure --help if there's some option that could influence this. Another option is to edit manually the makefile and remove this option.
== edit2 ==
One more thing
-L~/deps/A/lib -L~/deps/B/lib ~/deps/A/lib/libA.so ~/deps/B/lib/libB.so
If libA.so and libB.so don't have SONAME, linking them like "~/deps/A/lib/libA.so" will also cause saving the path. Soname is set using -Wl,-soname,<soname> linker option when building shared library.
If soname is set in the shared library, linking it using "~/deps/A/lib/libA.so" form is ok.
Like Jan mentioned in the comments, the better way is using "-Llibrary/path -llibrary_name" without rpath.
-L~/deps/A/lib -L~/deps/B/lib -lA -lB
When I run ldd libB.so it gives:
libA.so.2 => /home/alex/dev/A-install/lib/libA.so.2
The low-level solution to this problem is to use the option "-soname=libA.so" when you link the libA.so library. By having SONAME defined for a shared object, the linker will not embed absolute paths when linking against that shared object.
The OP is using "configure", so this isn't an easy solution to implement unless he is willing to go into the bowels of the Makefile generated by the configure script.
Shared libraries and executables have a list of directories to look for shared libraries, in addition to the list in the operating system's configuration. RPATH is used to add shared library search paths, used at runtime.
If you want a relative path to be used in RPATH, there is a special syntax that most Linux/UNIX (but not AIX) systems support - $ORIGIN or ${ORIGIN}.
$ORIGIN will expand at runtime to the directory where the binary resides - either the library or executable.
So if you put executable binaries in prefix/bin/ and shared libraries in prefix/lib/ you can add an entry to RPATH like ${ORIGIN}/../lib and this will expand at runtime to prefix/bin/../lib/
It's often a little trick to get the syntax correct in a Makefile, because you have to escape the $ in ORIGIN so it will not be expanded. It's typical to do this in a Makefile:
g++ -Wl,-rpath=\$${ORIGIN}/../lib
Both Make and the shell will want to look in your environment for a variable called ORIGIN - so it needs to be double-escaped.
I just got caught out thinking I had the same problem.
None of the above answers helped me.
Whenever I tried
ldd libB.so
I would get in the output:
libA.so.1 => /home/me/localpath/lib/libA.so.1.0
and so I thought I had a hardcoded path. Turns out that I had forgotten I had LD_LIBRARY_PATH set for local testing. Clearing LD_LIBRARY_PATH meant that ldd found the correct installed library in /usr/lib/
Perhaps using the -rpath and -soname options to ld could help (assuming a binutils or binutils.gold package for ld on a recent Linux system)?
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.