I'm trying to link a game library for my game project in C++. I am using the g++ compiler and Atom Code Editor. Also on a Windows machine.
To link the library it needs to link those things:
Include path
Library path
Additional dependencies
The main.cpp file is at ProjectRoot/src/main.cpp and the library is at ProjectRoot/deps/lib_name
Inside the library there is and include folder, with the .h file for including, and a lib folder, with the .lib file. It's a static linking library.
So far, I've tried the following commands:
g++ -o ExecutableName.exe -I /deps/lib_name/include -L /deps/lib_name/lib src/main.cpp
Well, that didn't work though... It said that there was no such file or directory as library_name.h...
I need to know if I'm doing anything wrong and also how to specify the additional dependencies.
Every thing is correct . You just forgot to link the libraries . Do it as follows -
g++ -o ExecutableName.exe -I /deps/lib_name/include -L /deps/lib_name/lib src/main -l[library name] -l[library name]
Related
I'm compiling a c++ program using g++ and i am using two libraries called libsdl2-dev and libsdl2-image-dev
I installed both these libraries in my ubuntu machine with the commands
apt install libsdl2-dev libsdl2-image-dev and when I compile the program everything works fine. Then I copied these libraries from /usr/lib/x86_64-linux-gnu/ to my working dir with the binary file to be able to give this folder to someone else.
The problem comes when the user that hasn't installed these libraries tries to open my program by writing ./main (the binary file). Since he hasn't installed these libraries he would get an error like "can't open shared object: no such file or directory".
This happens because the binary file looks for these libraries in /usr/lib etc...
What i need
I need that my binary file looks for these libraries in the same folder,and not in /usr/lib/x86 etc.., from what I read I have to do something like rpath
The IDE used is Sublime Text and the syntax used to compile all my files is this:
g++ -c src/*.cpp -std=c++14 -m64 -g -Wall -I include && g++ *.o -o bin/debug/main -lSDL2main -lSDL2 -lSDL2_image && ./bin/debug/main`
Structure of folders
I got the project dir with and inside that i got 4 more directories, each one called: bin (with the debug subdirectory, where we got the final compile), include (with hpp files), res (with all textures), and src with all cpp files to compile, the other files are project files and .o files
I'm using Ubuntu 20.04-2 LTS and the same is for the other user's PC
Thanks in advance for any help!
That's because the dynamic linker loading runtime dependencies looks for them in some specified locations, which are "by default" your system library directories (where those libraries got installed by apt).
The other user should ideally install those libraries too (which could be done "automatically" if you build a .deb package with proper dependencies)
Otherwise you would have to change the runpath of your program by adding -Wl,-rpath='$ORIGIN', which makes the dynamic linker look for dependencies just where the binary is located.
$ORIGIN here is a special variable meaning "this executable" which is what you wanted to achieve.
see rpath
and A description of RPATH $ORIGIN
I found a way to resolve!
I used the program patchelf to add an rpath to my directory (linked to the binary file) now everything works
use ldd ./bin/debug/main to check the library
export LD_LIBRARY_PATH =$LD_LIBRARY_PATH:"your library path"
run the program,if this is not work. use patchelf to change the rpath to you r library
I have a simle file main.cpp and static library MyLib.lib and I am trying to link program against static library like this:
g++ -o m main.cpp -static -L c:\lib\path -l MyLib
or like this:
g++ -o m main.cpp -L c:\lib\path -Wl,-Bstatic -l MyLib -Wl,-Bdynamic
The compilation process exits successfully and without error. However when I try to run m.exe from command line I get error that it cannot be run because MyLib.dll cannot be found.
I specificaly said it should compile against static lib MyLib.lib so why is it searching for a dynamic library? Did I made an error in commands above?
It really looks like you linked with a shared library.
You need to add the location of the folder containing MyLib.dll to the PATH.
In a Command Prompt type this:
SET PATH=<dll_location>;%PATH%
m.exe
or make sure MyLib.dll is in the same folder as m.exe.
If gcc only finds a shared library there is a chance the static flags didn't work.
Why is your library not called libMyLib.a? The name MyLib.lib seems to imply you got it prebuilt from MSVC. If so, how do you know MyLib.lib is not a shared library?
Is there a way you can build MyLib yourself as a static library?
I am currently trying to link a library using MinGW with the following command:
g++ main.cpp -l"C:\Users\Trent\Desktop\glfw3"
This command does not work, however the following does:
g++ main.cpp -lglfw3
Because of this, I think the compiler is probably searching for glfw3.dll in C:\Users\Trent\Desktop\C:\Users\Trent\Desktop which obviously doesn't exist. Is there a way to tell G++ to search for a library using an absolute path rather than a relative one?
P.S. The main.cpp file contains no code, I am simply just trying to link a DLL before I actually write anything.
For gcc family -l is option to specify library name, it searches names in system folders (defined in environment), you can add folders to lookup list by the -L option, just like VTT commented.
I have been using Boost (the header only library part) for sometime now. I recently started on a project that required the compiled libraries (filesystem etc).
I followed the instructions given in the documentation, and was under the impression that the libraries to installed (directly) in the usr/local folder. After a lot of trial and error, I found that the correct (*.a) files to use were in:
/usr/local/boost_1_45_0/stage/lib/
Is this the correct folder to use for linking the boost built shlibs (shared libraries)?
An example for linking regex static(*.a) lib:
g++ -I /usr/local/boost_1_45_0 -c your_regex_prog
g++ -static -o static_regex your_regex_prog.o -lboost_regex
I have a shared library that I wish to link an executable against using GCC. The shared library has a nonstandard name not of the form libNAME.so, so I can not use the usual -l option. (It happens to also be a Python extension, and so has no 'lib' prefix.)
I am able to pass the path to the library file directly to the link command line, but this causes the library path to be hardcoded into the executable.
For example:
g++ -o build/bin/myapp build/bin/_mylib.so
Is there a way to link to this library without causing the path to be hardcoded into the executable?
There is the ":" prefix that allows you to give different names to your libraries.
If you use
g++ -o build/bin/myapp -l:_mylib.so other_source_files
should search your path for the _mylib.so.
If you can copy the shared library to the working directory when g++ is invoked then this should work:
g++ -o build/bin/myapp _mylib.so other_source_files
If you are on Unix or Linux I think you can create a symbolic link to the library in the directory you want the library.
For example:
ln -s build/bin/_mylib.so build/bin/lib_mylib.so
You could then use -l_mylib
http://en.wikipedia.org/wiki/Symbolic_link