I have cross-compiled a simple hello world application for Linux running on ARM platform. If I use static linking the application runs fine on the target.
However, when I use dynamic linking using the shared libraries, I understand that I need to put the dependent libraries on target (ex: libc.so.6 and libgcc_s.so.1).
I have set the env.variable LD_LIBRARY_PATH to :/usr/local/lib where I have copied the .so files.
When I run the application on my target now I get
-sh: ./a.out: not found
... every single time. I would like to ask if I have done anything wrong, or is there a simple way to do this?
Related
This may be a noob question, but I have been stuck trying to work out how to statically build my qt project on linux. I tried doing what it said on http://doc.qt.io/qt-5/linux-deployment.html , but I do not understand the 1st step. When I cd to the location of my qt project and run
cd /path/to/Qt
./configure -static -prefix /path/to/Qt <otherparameters>
make
it says no such file or directory. Am I misunderstanding what paths I need to use? I want to make my qt project a stand alone executable which doesnt require the computer it is on to have qt. I have read about dynamically linking the libraries, but I dont really know what to do with that either. The deploy option is greyed out in qtcreator, is there a way to use this?
Thanks
/path/to/Qt should be the path to Qt's sources, not your project's. That section of the documentation is about building Qt statically, which you must do before trying to statically link your application to Qt. For example, if you downloaded/cloned the sources to /home/jxb458/qt5, then you'd replace /path/to/Qt with that:
cd /home/jxb458/qt5
./configure -static -prefix /home/jxb458/qt5/qtbase
make
Static linking is great when it works, but it can be an effort - I have found especially when using GUI. As Mitch said you need to actually re-build the Qt source code
I made some notes back when I was building statically quite a bit here: Notes on static building (derived from many sources) they should at least point you in the right direction - you can probably ignore the part about installing Ubuntu - the notes assume a new install.
However I have more recently returned to the dynamic linking deployment since I feel this is a better way to deploy now. You don't need to install Qt on the target machine you just need to collect the qt dlls and copy them with your application (using ldd executable-name which produces a list of dlls you need - but just take the Qt ones not the system/generic ones). For plugins you need to do a bit more (but its fairly simple). I even wrote a bash script to do this automatically (i'll send it to you if you need it), in windows there is a qt script called windeployqt (not sure why there is not a linux variant).
If I where to start again looking into deployment I would go for dynamic linking. Maybe try with a simple project to start with (like a hello world proj).
I am working on bindings for a cpp library.
To do this I wrote a capi / wrapper for the library and compiled that to a shared lib (.so file).
My question is, how do I then use and integrate this file into cargo without forcing the user to install it? Currently I build the cpp via a Makefile called from the build variable in Cargo.toml, but I am unsure what to do with the compiled lib.
For testing, I can either use rpath or LD_LIBRARY_PATH to point the executable to the right location, but this will not work when distributing a library.
How are people managing this?
First of all, determine whether you really need a shared library. It's not clear from your question, but if you compiled your own wrapper into a shared library, that's probably unnecessary - you can compile your code into a static library and link it directly into your executable.
Moreover, you can try to link that third-party library statically too. I don't think this should be hard. And yes, you need to use build command in the manifest to do all of this now.
However, if you still need to use a shared library and you don't want the end user to install it herself (which is strange, because that's the point of shared libraries), you have to distribute it manually. For example, you can write a makefile which assembles an archive which your users may extract and use. For your program to find the library correctly you will either have the user to install this archive into the system root directory (e.g. /usr on linux; then this shared library will be located automatically) or you will have to write small shell script wrapper around your executable which will locate the shared library and set appropriate LD_LIBRARY_PATH.
I'd go for the first path. Usually all major platforms provide means to create installation packages (deb/rpm/pkg.tar.xz/whatever on Linux, brew on Mac, windows installer on Windows, though on Windows you can just put your shared library in the same directory as the executable and it will work). You just have to create packages for the platform your users work on, so your program will be installed in correct directories and your shared library will be resolved automatically.
I am working on a cross platform, building on PC running on ARM.
I have several targets with different sets of shared libraries.
I am building a single executable which is linked with all the shared libraries.
I can't run it on targets that some shared libraries missing on. I get loader error.
Is there a way to 'tell' the loader to ignore the missing shared libs?
I will deal the the missing functions in run-time, I really need one executable..
No. You cannot tell the dynamic loader to ignore missing libraries.
What you can do is load the libraries dynamically using functions like dlopen and dlsym.
I have read that .so is a dynamic library file and .a is a static library file.
While building openssl i gave the option ./Configure no-shared and it created a lot of .a files.
So, my question is will the other packages like apache will be able to use .a files from openssl?
for example libcrypto.a,
someone please advice me if im going enirely through wrong path.
Basically the static library can be compiled into another application at link time. In your example Apache could use libcrypto.a during build time and include it in the Apache httpd application.
A dynamic .so library can be loaded and unloaded at runtime and you have a better flexibility to change what Apache should support without recompiling the Apache binaries.
Using Apache as example the dynamic loading of .so files are described in the Dynamic Shared Object (DSO) section in the documentation. You can also find links to the installation section which describe how to include static libraries at build time.
There is a good question about this that could be good to read, and that provide mote details in the subject.
Difference between shared objects (.so), static libraries (.a), and DLL's (.so)?
If A.a is static library and two different programs want to use it. A.a is created two times for each program. while If A.so is dynamic library than two programs access same file.
Its mean that you are using reference in library.
If your library is going to be shared among several executables(like apache and openssl), it often makes sense to make it dynamic to reduce the size of the executables. Otherwise, definitely make it static.
In your case you must create dynamic library
Please read -
http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html.
It is a very good tutorial with example.
you will learn -
what is static library (.a) and how to make it.
what is shared library (.so) and how to make it.
difference with .ddl (windows os)
I am developing cross-platform Qt application.
It is freeware though not open-source. Therefore I want to distribute it as a compiled binary.
On windows there is no problem, I pack my compiled exe along with MinGW's and Qt's DLLs and everything goes great.
But on Linux there is a problem because the user may have shared libraries in his/her system very different from mine.
Qt deployment guide suggests two methods: static linking and using shared libraries.
The first produces huge executable and also require static versions of many libraries which Qt depends on, i.e. I'll have to rebuild all of them from scratches. The second method is based on reconfiguring dynamic linker right before the application startup and seems a bit tricky to me.
Can anyone share his/her experience in distributing Qt applications under Linux? What method should I use? What problems may I confront with? Are there any other methods to get this job done?
Shared libraries is the way to go, but you can avoid using LD_LIBRARY_PATH (which involves running the application using a launcher shell script, etc) building your binary with the -rpath compiler flag, pointing to there you store your libraries.
For example, I store my libraries either next to my binary or in a directory called "mylib" next to my binary. To use this on my QMake file, I add this line in the .pro file:
QMAKE_LFLAGS += -Wl,-rpath,\\$\$ORIGIN/lib/:\\$\$ORIGIN/../mylib/
And I can run my binaries with my local libraries overriding any system library, and with no need for a launcher script.
You can also distribute Qt shared libraries on Linux. Then, get your software to load those instead of the system default ones. Shared libraries can be over-ridden using the LD_LIBRARY_PATH environment variable. This is probably the simplest solution for you. You can always change this in a wrapper script for your executable.
Alternatively, just specify the minimum library version that your users need to have installed on the system.
When we distribute Qt apps on Linux (or really any apps that use shared libraries) we ship a directory tree which contains the actual executable and associated wrapper script at the top with sub-directories containing the shared libraries and any other necessary resources that you don't want to link in.
The advantage of doing this is that you can have the wrapper script setup everything you need for running the application without having to worry about having the user set environment variables, install to a specific location, etc. If done correctly, this also allows you to not have to worry about from where you are calling the application because it can always find the resources.
We actually take this tree structure even further by placing all the executable and shared libraries in platform/architecture sub-directories so that the wrapper script can determine the local architecture and call the appropriate executable for that platform and set the environment variables to find the appropriate shared libraries. We found this setup to be particularly helpful when distributing for multiple different linux versions that share a common file system.
All this being said, we do still prefer to build statically when possible, Qt apps are no exception. You can definitely build with Qt statically and you shouldn't have to go build a lot of additional dependencies as krbyrd noted in his response.
sybreon's answer is exactly what I have done. You can either always add your libraries to LD_LIBRARY_PATH or you can do something a bit more fancy:
Setup your shipped Qt libraries one per directory. Write a shell script, have it run ldd on the executable and grep for 'not found', for each of those libraries, add the appropriate directory to a list (let's call it $LDD). After you have them all, run the binary with LD_LIBRARY_PATH set to it's previous value plus $LDD.
Finally a comment about "I'll have to rebuild all of them from scratches". No, you won't have to. If you have the dev packages for those libraries, you should have .a files, you can statically link against these.
Not an answer as such (sybreon covered that), but please note that you are not allowed to distribute your binary if it is statically linked against Qt, unless you have bought a commercial license, otherwise your entire binary falls under the GPL (or you're in violation of Qt's license.)
If you have a commercial license, never mind.
If you don't have a commercial license, you have two options:
Link dynamically against Qt v4.5.0 or newer (the LGPL versions - you may not use the previous versions except in open source apps), or
Open your source code.
The probably easiest way to create a Qt application package on Linux is probably linuxdeployqt. It collects all required files and lets you build an AppImage which runs on most Linux distributions.
Make sure you build the application on the oldest still-supported Ubuntu LTS release so your AppImage can be listed on AppImageHub.
You can look into QtCreator folder and use it as an example. It has qt.conf and qtcreator.sh files in QtCreator/bin.
lib/qtcreator is the folder with all needed Qt *.so libraries. Relative path is set inside qtcreator.sh, which should be renamed to you-app-name.sh
imports,plugins,qml are inside bin directory. Path to them is set in qt.conf file. This is needed for QML applications deployment.
This article has information on the topic. I will try it myself:
http://labs.trolltech.com/blogs/2009/06/02/deploying-a-browser-on-gnulinux/
In a few words:
Configure Qt with -platform linux-lsb-g++
Linking should be done
with –lsb-use-default-linker
Package everything and deploy (will
need a few tweaks here but I haven't yet tried it sorry)