Here's my dilemma: I'm attempting to create a .dll version of my project. This project uses the V8 and CURL libraries which are currently built as debug .libs. I'd like to package all of them up in a single DLL that can be shared (I understand I need to alter my code with __declspec(dllexport) but that's a separate issue) to others.
Do I need to compile the V8 and CURL libraries as DLLs then somehow wrap them up in my own DLL?
If you have a .lib with no .dll for the CURL libraries, then they are most certainly static libraries. When you link them to your DLL, the code from these libraries is linked into your DLL.
I've generally had to include the source for the dependencies (in your case both V8 and CURL) in my project and build that way to get them completely incorporated without extra headaches.
If you have libs and you link to those you SHOULD get them merged though.
Related
The Android app I am working on is completely written in C++. I need to integrate it with a static library that also is written in C++. There is no dependency on STL in any of the projects.
The static library uses cmake to build. Unfortunately, the app is based on an old AOSP version of Android NDK and has no support for cmake.
I also have a newer version of Android NDK in a different directory. This version does support cmake toolchains.
I am thinking I will build the static library against the new NDK and use it in my main project. The ABI is the same for both the projects - armv7a.
I have tested this logic with a sample code. It seems to work. I am able to invoke methods in the static library from my main app.
Also, there are no name-mangling issues.
The question I have is if there is any issue I am overlooking.
I am thinking it should not matter that the compilers used to build the sources are different. As long as they are producing arm-compatible code, I should be able to able to integrate them.
As a matter of fact, another library that I am using, gstreamer, is available for download as pre-built binaries at https://gstreamer.freedesktop.org/data/pkg/android.
Please advice.
For those interested, mixing NDKs doesn't seem to be an issue as long as you follow certain guidelines. Some of them are listed at https://developer.android.com/ndk/guides/cpp-support.
Essentially, there is no problem if your project is 'C' based. However, if you are using C++, you must not use STL.
I have managed to build part of my code with two NDKs and I am not seeing any link time or runtime errors.
I'm working on a project, which targets both Windows and Linux (and possible in the future MacOS). It consists of some applications with several shared libraries. It is written in modern C++ and modern CMake. It also uses 3rd-party libraries like Qt, OpenCV, Boost, GraphicsMagick, samplerate, sndfile. Those dependencies are handled through Conan package manager. I'm building both on Linux (Ubuntu 18.04, GCC 8.1) and Windows (via WSL - also Ubuntu 18.04, MinGW-w64 8.1). I'm using fairly recent versions of 3rd-party libraries with custom built options (strictly speaking - different versions than available on Ubuntu's APT, e.g. Qt v5.11.3, or custom built of GraphicsMagick)
I'm using CPack. On Windows I'm building NSIS installer, but on Linux I would like to use DEB generator (may be other if needed). All of my targets (written apps and shared libs) have appropriate CMake's INSTALL configurations, so they are copied correctly into the generated installers (component based installation). The real problem comes with packaging of 3rd-party dependencies.
Problem
Strictly speaking, I have no idea, how to do it well using CMake+CPack+Conan, both on Linux and Windows. I've read a lot of articles and posts, but I'm stucked. I would like to have something, that automatically bundles into the installer all 3rd party libraries used by project with needed plugins and, what is the most important, with needed system/compiler libraries (libgomp, libstdc++ and so on).
Possible solution
To my surprise, on Windows, this task is fairly easy, because every DLL used by app (my libs, 3rd-party libs and system/compiler libs) needs to be located where executable is. I'm engaging Conan into this, by importing all used DLLs into bin directory. In the end, in most naive way of packaging, I will just copy the bin directory into the installer and it should work. But I'm not sure, if this approach is OK.
On Linux, things are more complicated. First, there is arleady a package manager. Unfortunately, libraries/compilers available there are too old for me (e.g. on APT there is only Qt 5.9.6 ) and are built using different compile options. So, the only way for me is to ship them with my software (like in Windows). There are also issues with searching for dynamic libraries by ld, RPATH handling and so on. At the moment, the only solution I see is to write something like 'launcher' for my app, which sets LD_LIBRARY_PATH before program starts. After that, in this case we can just copy bin or lib directory to the DEB installer and this should work. But still, I don't know if this is correct approach.
Other solutions
I've also looked into other solutions. One of them was BundleUtilities from CMake. It doesn't work for me. It has a lot of problems in recognizing, whether some library is system or local one. Especially in WSL, where it stucked in processing dependencies to USER32.dll, KERNEL32.dll. BundleUtilities in Windows worked for me only with MSYS, but in MSYS I've failed to compile some 3rd-party libraries (GraphicsMagicks via Conan) and that's the reason, why I'm using WSL.
Summary
I'm looking for good and verified method of packaging C++ projects with multiple apps, libs and shipped 3rd-party libs, both for Windows and Linux. How are you doing things like this? Are you just copying bin and/or lib dirs to the installers? How (in terms of CMake/CPack code) are you doing that? INSTALL(DIRECTORY ...), or similar? I'm not sure, but I think that this problem should be already solved in the industry. ;)
Thanks for all suggestions.
First, Conan is a package manager for development, not for distribution, that's why you didn't find an easy way to solve your problem. Second, most of discussions are made at Conan issue, including bugs and questions. There you will find a big community + Conan devs which are very helpful.
with needed system/compiler libraries
This is not part of Conan. Why you don't use static linkage for system libraries?
Talking about CPack, we have an open discussion about it usage with Conan: https://github.com/conan-io/conan/issues/5655
Please, join us.
I see few options for your case:
on package method, run self.copy and all dependencies from self.cpp_deps, which includes all libraries, so you can run Cpack
Use Conan deploy generator to deploy all artifacts, and using a hook you can run cpack or any other installer tool
Out friend SSE4 is writing a new blog post about Deployment + Conan, I think it can help you a lot. You can read a preview here.
Regards!
I have windows dynamic linked library which I want to access from Linux environment. I don't have the source code of that library, so I cannot build .so file.
Is there a way by using Winelib or any other library or tool for converting library file to .so file, so that I can call functions defined in that library?
There is no easy way to do it, because the DLL cannot run in Linux enviromnemt all by itself. It will probably rely on user32.dll msvcrt.dll and friends at runtime, so you'll have to provide those files as well.
You can use winelib, but it doesn't just convert a .dll to an .so. You'll have to link the whole project that wants to call the DLL against winelib, and include the DLL itself with your app at runtime. If you are trying to port a Windows app to Linux, winelib will be able to convert your makefile for you, but it's far from automatic for complex projects.
I have a c++ library ported to linux.
Now I'm adding a JNI code so I can add a java wrapper.
The question is:
Is adding JNI to the same lib will effect the c++ application of the users --> So might it become not working if java not installed ... etc (Because it links to some code in jni.h and other stuff)?
It won't affect the current library if you add JNI to your library. JNI are a collection of interfaces and callback that make your library can be used by JVM. Without JNI, your library can't be used from JVM.
Your library will grow up in size and more symbols be exported when you add JNI.
By adding JNI to your current library, it means your library can be used as a normal library meanwhile can be loaded from JVM.
You may wish to consider creating a JNI wrapper in C/C++ and statically link to your current library. That way your currently library will still work for C/C++ apps and your code will be easier to debug and maintain. If you choose this route, you may also want to look into enabling link-time optimization for your JNI wrapper. Alternatively you could also dynamically link the JNI wrapper and just put both libraries in /lib (or where ever is appropriate), but you will have a runtime dependency on that base library.
For a cross-platform software project that builds on Linux and Windows we have distinct ways to handle third-party libraries. On Linux we build and link against the versions distributed with the CentOS/RHEL distribution, which means we link against release builds, whereas on Windows we maintain our own third-party library "packages" and on Windows we build two versions of every library - a release version that links msvcr100 and msvcp100 and a debug version that links msvcr100d and msvcp100d.
My question is simply whether it is necessary to build the debug version of the third-party dependencies on Windows or can we simply use /nodefaultlib:msvcr100 when building debug builds of our own software.
A follow up question: Where can I learn about good practices in this regard. I've read the MSDN pages about the msvc runtime, but there is very little there in terms of recommendations.
EDIT:
Let me rephrase the question more concisely. With VS2010, what is the problem with using /nodefaultlib:msvcr100 to link an executable build with /MDd when linking with libraries that are compiled with /MD.
My motivation for this is to avoid to have to build both release and debug version of third party libraries that I use. Also I want my debug build to run faster.
From the document for /MD, /MT, /LD (Use Run-Time Library):
MD: Causes your application to use the multithread- and DLL-specific version of the run-time library. Defines _MT and _DLL and causes the compiler to place the library name MSVCRT.lib into the .obj file.
Applications compiled with this option are statically linked to MSVCRT.lib. This library provides a layer of code that allows the linker to resolve external references. The actual working code is contained in MSVCR100.DLL, which must be available at run time to applications linked with MSVCRT.lib
/MDd: Defines _DEBUG, _MT, and _DLL and causes your application to use the debug multithread- and DLL-specific version of the run-time library. It also causes the compiler to place the library name MSVCRTD.lib into the .obj file.
So there is no documentation for any difference done to the generated code other than _DEBUG being defined.
You only use the Debug build of the CRT to debug your app. It contains lots of asserts to help you catch mistakes in your code. You never ship the debug build of your project, always the Release build. Nor can you, the license forbids shipping msvcr100d.dll. So building your project correctly automatically avoids the dependency on the debug version of the CRT.
The /nodefaultlib linker option was intended to allow linking your program with a custom CRT implementation. Quite rare but some programmers care a lot about building small programs and the standard CRT isn't exactly small.
Some programmers use the /nodefaultlib has a hack around a link problem. Induced when they link code that was built with Debug configuration settings with code built with Release configuration settings. Or link code that has incompatible CRT choices, /MD vs /MT. This can work, no guarantee, but of course only sweeps the real problem under the floor mat.
So no, it is not the proper choice, fixing the core problem should be your goal. Ensure that all your .obj and .lib files are built with the same compiler options and you won't have this problem. If that means that you have to pester a library owner for a proper build then pester first, hack around it only when you've discovered that you don't want to have a dependency on that .lib anymore but don't yet have the time to find an alternative.