I have compiled this library successfully. It generates a libcds2.la file that I am trying to link into my own project. I have all files (including the .h file) in the same directory as my project file. When I try to link and use the functions of said library, using:
g++ -o test -I/opt/include/ -L/opt/lib/ -lcds2 libcdsNoptrs.cpp util.cpp
comes back with
./test: error while loading shared libraries: libcds2.so.2:
cannot open shared object file: No such file or directory
whatever that is. But the point is that most of the time it just doesn't recognize the library. I assume I'm doing something wrong with the file paths, but can't figure it out. My test file is a C++ file including #include "libcds2/array.h" and everything is installed in opt/lib, opt/include, ugly, I know, but that's what the Makefile generated.
Any pointers?
The libtool .la is a 'meta data' file. After building the cds2 library, it's expected that libtool will also be used in 'link' mode to build any of the package's tests, etc.
Typically, the in the directory you find the .la file, you will find the .a and .so under the .libs subdirectory. The .libs/libcds2.a file will be found there, provided configure was given the --enable-static option (or it is enabled by default). But, my understanding is that you've installed the package in /opt :
g++ -I/opt/include/ libcdsNoptrs.cpp util.cpp -o test /opt/lib/libcds2.a
Otherwise, if libcds2 isn't installed, just supply a path to: .../libcds2/lib/.libs/libcds2.a
Unless you want to use libtool in --link mode with -static to handle everything. But learning the advantages of libtool is usually an exercise for a rainy day:)
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 $CXX .... The CXX is the environment variable set by the yocto script to set environment for cross compilation. Using CXX, you do not need to manually pass --sysroot
You should not link directly to pthread library with -lpthread. You should use -pthread
I'm trying to build the SDL library from the source code. I've downloaded the compressed file (i.e. SDL2-2.0.3.tar.gz) and extracted it. I don't want to install the files in /usr/local. According to this link, I need to change the configure
The last command says "sudo" so we can write it to /usr/local (by
default). You can change this to a different location with the
--prefix option to the configure script. In fact, there are a LOT of good options you can use with configure! Be sure to check out its
--help option for details.
This is what I've done.
mkdir build
cd build
../configure
make
sudo make install
In install folder that I've created are the following files
share
lib
include
bin
Now I would like to run the test files. I've picked this testatomic.c and this is the command line
gcc testatomic.c -o test -I/home/xxxx/Desktop/SDL2-2.0.3/install/include/SDL2 -L/home/xxxx/Desktop/SDL2-2.0.3/install/lib -lSDL2 -lSDL2main
I get this error
error while loading shared libraries: libSDL2-2.0.so.0: cannot open shared object file: No such file or directory
In lib, these are the files
Where is the shared object file?
You're getting error when running resulting program because system's dynamic linker cannot find required library. Program requires libSDL2-2.0.so.0, linker looks for it in system-defined directories (/lib, /usr/lib, ..., - defined in /etc/ld.so.conf), but finds none - hence an error.
To inform linker where you want it to look for libraries, you can define LD_LIBRARY_PATH environment variable, e.g. in your case:
export LD_LIBRARY_PATH="$HOME/Desktop/SDL2-2.0.3/install/lib"
./test
Other ways is installing libraries in standard location, defining LD_LIBRARY_PATH in your .bashrc (or whatever shell you use), or using rpath, e.g. adding -Wl,-rpath=$HOME/Desktop/SDL2-2.0.3/install/lib at the end of your compilation line.
I was able to fix this problem with:
sudo apt install libsdl2-dev
I too had:
./01_hello_SDL: error while loading shared libraries: libSDL2-2.0.so.0: cannot open shared object file: No such file or directory
as a result of compiling the first C++ program (using the SDL headers) as part of the Lazy Foo tutorial. I found out that libSDL2-2.0.so.0 was just using the find command in the GUI. It turned out to be in /usr/local/lib
Then in terminal I typed:
export LD_LIBRARY_PATH="/usr/local/lib"
I checked the value of LD_LIBRARY_PATH using:
echo $LD_LIBRARY_PATH
I recompiled (don't know if that was necessary) and voila, it worked.
I use gsl.
After I compiled my .cpp file and run it, I faced with below error:
error while loading shared libraries: libgsl.so.0: cannot open shared object file: No such file or directory
I found same as this problem in:
https://groups.google.com/forum/#!topic/cortex_var/6vluX7pP0Sk
&
Linux error while loading shared libraries: cannot open shared object file: No such file or directory
&
http://www.gnu.org/software/gsl/manual/html_node/Shared-Libraries.html
And I have done as in the above links wrote but the error is still remained.
Can anyone help me?
To make it work do the following steps
Start Borne Shell
$LD_LIBRARY_PATH= path to your gsl lib folder inside the gsl installation folder
$export LD_LIBRARY_PATH
now run your executable
It should work fine.
First, you need to locate the file (libgsl.so.0). You can do this, for example, by using the find command:
sudo find / -name "libgsl.so.0"
Let us assume, the file is located in /usr/local/lib.
(If the file has not been found, install the corresponding package or download the source, build it and install it.)
Now, you have two options:
(1) Quick & Dirty:
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
export LD_LIBRARY_PATH
This adds the path of the library to an environment variable. The disadvantage of this option is, that it is only valid for the current session. It will not work for other users. It will not work once you log off and on again.
(2) Permanent:
Review your /etc/ld.so.conf. If /usr/local/lib is not listed there, add it. Now, run ldconfig to detect the shared object file and add it to some system-wide index.
I got the same error with Krita on Arch Linux. I made a symlink with
ln /usr/lib/libgsl.so /usr/lib/libgsl.so.0
and that fixed it.
In my experience, fastStructure depends on gsl 1.6 but not the latest version.
wget http://gnu.mirror.vexxhost.com/gsl/gsl-1.6.tar.gz
tar -zxvf gsl-1.6.tar.gz
cd gsl-1.16
./configure
make
sudo make install
Add these lines to your .bashrc file on your home directory.
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
export CFLAGS="-I/usr/local/include"
export LDFLAGS="-L/usr/local/lib"
then, run source ~/.bashrc to set these environment variables.
It works fine when I change the version from the latest to the 1.6.
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/shg047/software/gsl/lib/
such as: to-mr: error while loading shared libraries: libgsl.so.19: cannot open shared object file: No such file or directory
Have you tried updating your library? The program I was trying to run simply needed a newer version of gsl (I had 1.9.5 while it needed 2.0.0 or newer).
If you are on arch you can run:
yaourt gsl
and select the appropriate one.
You can use gsl-config --libs in you makefile or in the command line when you link the gsl library. Just type gsl-config you can find the options it offers to you. Choose the options you need, you will find compile and link process much easier than before. As a result, when I type gsl-config --libs in my terminal, I get -L/usr/local/lib -lgsl -lgslcblas -lm. Although it is very simple, first you should know where you gsl is installed. You can add the directory to the PATH environment variable or use the absolute path to execute gsl-config .
I needed libgsl.so.19:
/snap/inkscape/current/bin/inkscape: error while loading shared libraries: libgsl.so.19: cannot open shared object file: No such file or directory
I solved it with:
Installing Anaconda
searched for libgsl.so.19 and found it in ~/anaconda3/lib
run LD_LIBRARY_PATH=$LD_LIBRARY_PATH:~/anaconda3/lib (best add it to ~/.basrc)
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.