This question already has answers here:
How to install c++ library on linux
(2 answers)
Closed 4 years ago.
I'm new to c++ and don't understand how to install a library on Linux (Mint). I want to use the GNU GMP library:https://en.wikipedia.org/wiki/GNU_Multiple_Precision_Arithmetic_Library
I downloaded the tar.lz file and installed it with
./configure
make
sudo make install
If I try to compile it, I get the error message that the header file "gmpxx.h" wasn't found. Where can I find this file? How do I compile it with the -lgmpxx -lgmp flags? I tried something like:
g++ test.cpp -o test -lgmpxx -lgmp
If the library is using the Autoconf system (which your does) then the default installation prefix is /usr/local.
That means libraries are installed in /usr/local/lib, and header files in /usr/local/include. Unfortunately few Linux systems have those added for the compiler to search by default, you need to explicitly tell the compiler to do it.
Telling the compiler to add a header-file path is done using the -I (upper-case i) option. For libraries the option is -L.
Like so:
g++ test.cpp -I/usr/local/include -L/usr/local/lib -lgmpxx -lgmp
The above command will allow your program to build, but it's unfortunately not enough as you most likely won't be able to run the program you just built. That's because the run-time linker and program loader doesn't know the path to the (dynamic) libraries either. You need to add another linker-specific flag -rpath telling the build-time linker to embed the path inside your finished program. The front-end program g++ doesn't know this option, so you need to use -Wl,-rpath:
g++ test.cpp -I/usr/local/include -L/usr/local/lib -lgmpxx -lgmp -Wl,-rpath=/usr/local/lib
The options can be found in the GCC documentation (for the -I and -L and -Wl options), and the documentation for ld (the compile-time linker) for the -rpath option.
If you install a lot of custom-build libraries, you might add the path /usr/local/lib to the file /etc/ld.so.conf and then run the ldconfig command (as root). Then you don't need the -rpath option.
Now with all of that said, almost all libraries you would usually use for development will be available in your distributions standard repository. If you use them the libraries will be installed with paths that means you don't have to add flags.
So I recommend you install your distributions development packages for the libraries instead.
Related
I'm trying to compile a shared library I wrote in C++ to use a specific version of another shared library in the current directory, however it seems to be ignoring that and it uses the (older and incompatible) .so file in my LD_LIBRARY_PATH at runtime. How would I go about overriding the .so file it uses to use my own? I also need to retain the older version for another use on the same system.
Here's my command I'm using to compile: clang++ /data/openpilot/selfdrive/df/libs/libSNPE.so -lsymphony-cpu -lsymphonypower -I/data/openpilot/phonelibs/snpe/include -std=c++14 -lstdc++ -fPIC -o d_f.so dynamic_follow.cc -shared
/data/openpilot/selfdrive/df/libs/libSNPE.so being the library I want to use.
I also tried to use the -l flag before my library file, however it returns cannot find -l/data/openpilot/selfdrive/df/libs/libSNPE.so
Confirmed to still use the library in LD_LIBRARY_PATH with this command as well: clang++ -Wl,-rpath,/data/openpilot/selfdrive/df/libs -L/data/openpilot/selfdrive/df/libs -lSNPE -lsymphony-cpu -lsymphonypower -I/data/openpilot/phonelibs/snpe/include -std=c++14 -stdlib=libc++ -fPIC -o d_f.so dynamic_follow.cc -shared
The -L flag tells where to look for libraries at link time, while LD_LIBRARY_PATH tells where to look for libraries at run-time. So whatever path you set at link-time, this will be ignored when running the executable.
You need to have LD_LIBRARY_PATH include the directory of your dynamic library at run-time for your executable to find it. So you may run your executable like this:
LD_LIBRARY_PATH=/data/openpilot/selfdrive/df/libs:"$LD_LIBRARY_PATH" ./your-exec
I downloaded chilkat and I need to build it... I got 2 .sh files. The README says:
To build the C and C++ samples, first edit the c_sampleBuild.sh and
linkSample.sh scripts and set the "-L" option's path for the system libraries.
LinkSample.sh:
g++ -Wl,--enable-auto-import linkSample.cpp -o"linkSample.exe" -L. -libchilkat-9.5.0 -L/c/MinGW/lib -lcrypt32 -lws2_32 -ldnsapi
c_sampleBuild.sh:
#!/bin/bash -ev
gcc -c c_Sample.c -o"c_Sample.o"
g++ c_Sample.o -o"c_Sample.exe" -L. -lchilkat-9.5.0 -L/c/MinGW/lib -lcrypt32
-lws2_32 -ldnsapi
It's now clear how I should make that.... Help please :) Thanks
You haven't said what platform you are building on. But if you are using Windows + MinGW then:
The libraries for crypt32, ws2_32 and dnsapi can be downloaded from: here
For the g++ command, the -l (lowercase) option tells g++ which additional libraries you want to link against, and the -L (uppercase) option is used to tell g++ where to look for the libraries.
If you have a library file called libbar.a in the current folder (.) then you add the option (-L. -lbar)
Or, if you have a library in /path/to/foo/libbar.a then you add (-L/path/to/foo -lbar).
You will need to check the MinGW documentation for the locations of the system libraries, they are likely to be found in /lib or /usr/lib.
I installed Boost via sudo apt-get install libboost-all-dev on the most recent version of Ubuntu. Now I want to compile a project that uses the Boost.Serialization library, which needs to be linked.
I've tried many variants of the following, without success:
gcc -I /usr/lib code.cpp -o compiled /usr/lib/libboost_serialization.a
and
gcc -I /usr/lib code.cpp -o compiled -l libboost_serialization
The error message is:
error: ‘split_member’ is not a member of ‘boost::serialization
`
What am I missing?
You are having troubles with compiling your code, not linking. On that stage it has nothing to do with libraries. At that point the fact that you have to link against something is irrelevant.
Make sure you are including boost/serialization/split_member.hpp directly or indirectly and get your code compiled first.
On a side note, -I flag is used to specify path to include files and not libraries. For libraries, use -L. But if you have installed Boost from apt, then it should already be in the path and so no additional -I or -L should be required. And when you specify -l, you have to emit lib from the beginning of library name and not put a space between a flag and its argument. Assuming working code, something like this should do:
g++ code.cpp -o compiled -lboost_serialization
I'd also recommend you pass -Wall flag to make compiler be more verbose and warn you about possible mistakes in your code.
split member is a problem with compiling where boost is assuming there are split calls for serialize and deserialize.
http://www.ocoudert.com/blog/2011/07/09/a-practical-guide-to-c-serialization/
I'm having trouble building a simple c++ program that tests out regex's from the boost library. The problem that I'm having is occurring in the linking stage and I don't know enough to fix the error on my own.
In the .cpp program that uses regexes I used the following include line.
#include <boost/regex.hpp>
I don't know enough to figure out what command I should use to build the program using g++. I tried using the following command line (and variations of it) to build the program.
g++ -I/usr/include/regex -L/usr/lib -llibboost_regex main.cpp -o regex_test
Other information that might be relevant:
Operating system: Arch linux
g++ version: 4.6.2 20120120 (prerelease)
Any help would be appreciated.
Assume you have installed Boost with the boost and boost-libs packages,
The header <boost/regex.hpp> should exist in /usr/include/boost/regex.hpp. You don't need to use any -I flags since /usr/include should be included by default.
You shouldn't need the -L flag either since /usr/lib should also be included by default when linking.
When using the -l flag to link with a library libfoo.so, the leading "lib" part should be removed.
The command line should therefore be:
g++ main.cpp -o regex_test -lboost_regex
I'm trying to use openssl in a gcc program but it isn't working.
g++ server.cpp /usr/lib/libssl.a -o server
gives an error message, as does anything with the -l option. What must I type on the command line to link with openssl? The file /usr/lib/libssl.a exists, but nevertheless I still get the linker error no such function MD5() exists.
Without knowing the exact errors you are seeing, it is difficult to provide an exact solution. Here is my best attempt.
From the information you provided, it sounds as though the linker is failing because it cannot find a reference to the md5 function in libssl.a. I believe this function is actually in libcrypto so you may need to specify this library as well.
g++ server.cpp -L/usr/lib -lssl -lcrypto -o server
You or others may find this article developerWorks article helpful.
Secure programming with the OpenSSL API
https://developer.ibm.com/technologies/linux/tutorials/l-openssl
It describes most things you need to know to get off the ground with OpenSSL and C/C++. If you find you are following most of the same steps, it might help you see what needs doing.
Good luck.
update
revised link: https://developer.ibm.com/technologies/linux/tutorials/l-openssl
Which has been shuffled around
original link: http://www.ibm.com/developerworks/linux/library/l-openssl.html
Which now goes to a digest page including the article.
Note: keeping both links because they be used to find new discoveries.
In Eclipse IDE select Your Project property --> c/c++ Build --> Settings gcc c linker(from tools settings)--> add to Library Search Path (-L)
/usr/lib -lssl -lcrypto
The location of the library is not fixed. In my case (Ubuntu 18.04), the .a files are located in /usr/lib/x86_64-linux-gnu/. So here are the complete steps:
1) install the library,
sudo apt install libss-dev
2) check the installed files,
dpkg-query -L libssl-dev
3) change the gcc flags -L(library directory) -l(library name), e.g.,
gcc XXX.c XXXXX.c -L/usr/lib/x86_64-linux-gnu/ -lcrypto -lssl
On top of the accepted answers, I could not make compile the OpenSSL example for AES-CCM:
https://github.com/openssl/openssl/blob/master/demos/evp/aesccm.c
To make it work I needed to add two more things:
The Dinamic Linking Library : -ldl
The PThread library to use POSIX threading support: -pthread (Adding directly the library with -lpthread is not recommended )