I have downloaded a repository from github with a library with git clone
then I typed in terminal "make"
now I have a libmylibrary++.so file in folder mylibrary/src
Now I want to run a c++ file which uses the library but I can't compile it because of this error: "mylibrary.hpp: No such file or directory"
How to add it to PATH? yet I don't understand what exactly I need to add
Whether it is folder "/home/mylibrary" or folder with the .so file
Your C++ compiler only knows to search for header files and libraries in standard locations and directories. Just because you downloaded another library in some directory, somewhere, doesn't mean that your C++ compiler will automatically find it.
You will need to change your Makefile and compile your program with the additional compilation options that instruct your C++ compiler to search for header files and libraries in other directories -- typically -I and -L option.
Additionally, you will probably need to use either -R or -Wl,-rpath options in order for the compiled code to load the shared libraries from the non-standard locations.
You will find additional information in the gcc manual and documentation.
Related
The issue
I am trying to use the execution policies in the standard algorithm library. However, when I try to compile I get the following error message
c:\mingw\lib\gcc\mingw32\9.2.0\include\c++\pstl\parallel_backend_tbb.h:19:10: fatal error: tbb/blocked_range.h: No such file or directory
After looking at various other related questions such as this or this, I understand that the execution library depends upon a software called tbb. Moreover in order to compile code which uses <execution> one has to manually link to tbb. My issue is precisely with how to download and link tbb to a script that uses <execution>.
I believe I have some serious gaps in my understanding in terms of how one downloads the correct files and then links to them. I will first make a list with my understanding of the linking process and then I will explain what I have tried to fix the issue. I have chosen this format so that it is faster for the one to answer my question to point at the issue at fault. I will attempt to keep this as concise as possible.
My understanding
Code is organized in header and cpp files, where the former usually only contain the interface to the software and the later the implementation
The cpp files can be pre-compiled and grouped into a single library file
For a user to then use the library, they have to #include the header/s in their script and also tell the compiler where the header files as well as the library file, are located
This can be done with the -I for the headers and -L, -l for the library file
-L provides the location of the library files, the -l specifies which libraries to use
What I tried
The script I try to compile is:
#include <execution>
int main() {
std::execution::par;
return 0;
}
with
g++ script.cpp -o out -I C:(path to the headers) -L C:(path to the library) -l (name of library) -std=c++17
I should also mention I am trying to do this on Windows 10
1st attempt
I had a particularly hard time understanding where to find the header and library files for tbb.
In the Intel getting started with TBB webpage, this github repository is listed as "TBB being available at". As I am used to header-only libraries I thought everything would be in the include directory but no .dll files where there. It is now my understanding that I have to compile the DLLs myself for my specific system which makes sense. I followed the following process using cmake:
# Do our experiments in /tmp
cd /tmp
# Clone oneTBB repository
git clone https://github.com/oneapi-src/oneTBB.git
cd oneTBB
# Create binary directory for out-of-source build
mkdir build && cd build
# Configure: customize CMAKE_INSTALL_PREFIX and disable TBB_TEST to avoid tests build
cmake -DCMAKE_INSTALL_PREFIX=/tmp/my_installed_onetbb -DTBB_TEST=OFF ..
# Build
cmake --build
# Install
cmake --install .
# Well done! Your installed oneTBB is in /tmp/my_installed_onetbb
However at the cmake --build step, cmake does not accept the command but requests more options. One of them is the dir option, which for which I made another directory and supplied it but then the error message Error: could not load cache printed out.
In any case, some files had been created so I searched for the .dll file but could not find it.
2nd attempt
I downloaded the Intel oneAPI Base Toolkit as is suggested here. After the installation at ../Program Files (x86)/Intel/oneAPI I found the specific tbb tool at C:\Program Files (x86)\Intel\oneAPI\tbb and I used this address for the -I and -L flags but initial error message persists.
I also copied the directory C:\Program Files (x86)\Intel\oneAPI\tbb\2021.6.0 to the local directory of the script so I could link with -flag tbb\2021.6.0 but no luck
Many thanks
Yes you were correct.
By using the package mingw-w64-tbb. You can use -ltbb12 instead of -ltbb. As the library files are related to ltbb12.
For using -ltbb option, you should set the Intel oneAPI environment. It can be used by downloading Intel oneAPI Base Toolkit.You can set the environment by sourcing setvars.sh file using the below command.
source /opt/intel/oneapi/setvars.sh
I currently have my Other Linker Options as:
Unfortunately, this means that I can only ever run the executable when libsfml-dev is installed, which is undesirable for game development. Whenever I even change the Other Linker Options or Search Directories>Linker will cause an error along the lines of:
error while loading shared libraries: libsfml-graphics.so.2.2.0: cannot open shared object file: No such file or directory. I assume this error happens because the libraries are relative, so it is completely portable.
EDIT:
I am using Code::Blocks (as you can see from the image), and I would like to know how I can link to the libraries relatively. They link fine when it is run from Code::Blocks, but when I run the executable I get the above error. My current Code::Blocks options are:
Linker Options:
(Other linker options is empty)
Search Directories:
Your first linker options would be the correct ones.
The Library libsfml-dev is only required on the compile machine.
There must also be another package which actually supplies the .so files. That one will also be required on the machine running the executable unless you package those .so files with your executable. In that case you probably need a script that sets LD_LIBRARY_PATH to the local directory containing the packaged .so files and then executes your program.
I have seen several other answers in order to add a library to my C+= project in eclipse.I have tried to add the path to the linker in Miscellaneous section using -L"and the path of the folder" and -l"the name without the lib prefix in the begging and the .so at the end"
I try to add libxl library so i use -lxl (for libxl.so) and -L/home/username/libxl3.5.3.0/lib/ (which the location of the lib file).
I have also tried to give it under the Linker menu and adding the name and the path in the Libraries section.
I get error that: /usr/bin/ld does not find -lxl file and it returns error
I am using -static to linker in order to make an executable that has the all the libs included but when i do not use -static the problem with the lib resolves from build but still when i try to run the program i get error that i the program can not open shared file libxl.so cause the file does not exist.How can i fix this?
When you add the library name to a C++ project in eclipse, do not prefix it with -l. Eclipse will do this for you when it invokes the compiler. For example if you want the boost_regex library, just input boost_regex not lboost_regex. Eclipse will do the rest for you. Or in your specific case, just use xl not lxl. You don't need the - either, nor the -L before paths as erenon points out in the comment below. Note that the above applies to the method of adding libraries using the Project->Properties->C/C++ General->Paths and Symbols dialog form for adding libraries using the Libraries and Library Paths tabs.
You are trying to link statically to a shared library. In my experience I have always used *.a files rather than *.so files to employ static linkage. This other answer Static link of shared library function in gcc seems to suggest that you are not actually able to link statically to *.so files.
I am trying to install a C++ library (armadillo) in a unix cluster where I do not have root permissions.
I managed to compile the C++ libraries without user permissions by running the following make command:
make install DESTDIR=my_usr_dir
But then in the armadillo readme file it says:
where "my_usr_dir" is for storing C++ headers and library files. Make sure your C++ compiler is configured to use the sub-directories present within this directory.
The compiler the armadillo uses to install the libraries is gcc-4.8.1. I am not sure where the compiler was installed but it's loaded when I start my session in the unix cluster.
After installing armadillo I am trying to compile open source code that uses the armadillo libraries. This open source code also has a makefile.
However, when I go to the open source code and I type in:
make
it calls g++. How can I make sure g++ will recognize the armadillo libraries previously installed in my_usr_dir?
Currently I get the following error if I go to src and then type make:
opencode.cpp:28:21: fatal error: armadillo: No such file or directory
#include <armadillo>
^
compilation terminated.
make: *** [mmcollapse] Error 1
you can use
alias gcc="gcc -I./my_usr_dir/include -L./my_usr_dir/lib"
and so on in your .bashrc file. In that way, whenever you invoke gcc on the command line, the flags will be added before every other argument you enter on the command line
I think the readme file refers to the usage of the library headers and library files from applications. For those to be useful, the compiler/linker/loader (usually all driven by the "compiler") have to know where to find them. The compiler always looks in some default directories, such as /usr/include (for headers) and /usr/lib/ (for libraries), but they require root permission to write into. However, you can tell the compiler with the flag -Idirectory to search in directory directory for headers. For libraries use -l and -L (check the manual page of your compiler). You may also need to consider the LD_LIBRARY_PATH and LD_RUN_PATH environment variables, if you're using dynamic linking (shared object files).
This question looks similar to
How to specify non-default shared-library path in GCC Linux? Getting "error while loading shared libraries" when running
If you dont want to change the .bashrc
use -rpath as suggested in the post above.
gcc XXX.c -o xxx.out -Lmy_usr_dir -lXX -Wl,-rpath=my_usr_dir
-L is for static linking
-rpath for adding the directory to the linker search path
more on -rpath here
I don't understand -Wl,-rpath -Wl,
Dont bother to upvote the answer because this is really not an answer. I would have commented but i could not locate the add comment for your post.
Good day! I am running a c++ project main.cpp in eclipse. i want to use my existing .so file and link it in main.cpp. I am searching about this but cant find the right method for me. I'm using ubuntu. Thanks for any help!
To link against a library you need to supply the compiler(or the linker) a -l flag and the library name. For example, if you want to link against a library called libjustine.so, you would supply your compiler(gcc if C, g++ if C++) a flag -ljustine and then the compiler would instruct the linker to link against a file libjustine.so in the library path (usually at least /usr/lib/ and /usr/local/lib/).
However, if you want to define your own library directory, for example a lib/ directory inside your project directory, you need to use the -L flag and supply the desired library directory(relative to the current directory) that way, for example -L/lib/ so the compiler can instruct the linker to look for the desired library from lib/ instead of for example /usr/lib/ where it looks for the file by default.