I got a .h file, two .lib files, a .dll file and a tiny test project from a hardware vendor to talk to their hardware.
Compiling and running their test project works just fine. Noteworthy: they don't use the .dll. I can throw the dll-directory and all of it's content away, everything works just fine.
To start things off I simply copied the communication parts of their code (connect, disconnect and send a command) into my project. This is actually all that you can do. I have included the .h file and pointed to the directory containing the .lib files. Just like in the tiny test project. It all compiles, but when I try to run the project complains that it is missing the .dll file.
Can anybody explain what is happening? How are libs and dlls supposed to work?
All of this is on windows, VS2005. I compared the .vcproj files and could not find any significant differences.
The test project is statically linked - the lib is included in the exe.
Your project is dynamically linked - the dll is referenced and therefore needed at runtime.
See this Stack Overflow question for more information.
Basically the answer depends on whether you are going to use static or dynamic linking for your executable.
With static linking, you need the .h and .lib files but not the .dll files to compile and link. Your executable will be larger but you won't need any of the .h/.lib/.dll files during runtime.
With dynamic linking, you just need the .h files to compile and link. Your executable will be smaller but you will need one or both of the .dll files during runtime.
For a more detailed treatment of this from the Visual Studio perspective, check out http://msdn.microsoft.com/en-us/library/1ez7dh12.aspx -
"Dynamic linking differs from static linking in that it allows an executable module (either a .dll or .exe file) to include only the information needed at run time to locate the executable code for a DLL function. In static linking, the linker gets all of the referenced functions from the static link library and places it with your code into your executable."
Related
I am a question about dll use in linux. I have dll and .h file that work good in windows. But now I need to work this program in linux. If I write a .cpp file that
function call the dll file's function. Could I compiler this .cpp file to assembly or to .so file. Then I can use .so file without original dll file ?
If you have a DLL that builds on Windows, then provided the C++ code is portable, it should be possible to compile the same code on Linux to produce a shared library (.so file), which is Linux's equivalent to Windows DLLs. There is good background on this topic here.
If your source code (i.e. CPP or header files) uses #include for headers that are Windows-specific, you will have to make that code portable in order for Linux to build and run it. One approach is to just try compiling your code on Linux and see what errors arise. If you want to be more proactive, for C++ portability guidelines see here.
I have the following problem:
I need to build a static library (.lib) that can be provided with other source code in such a way that the project can be linked with it. However when I build the library in release mode, the build generates .pdb files and has full paths to them baked into the final .lib itself, making it unusable.
I don't necessarily care if it generates .pdb or not, but what setting should I change in the .vcxproj to make sure that the final release .lib doesn't require (or insert) absolute paths for those .pdbs?
I made an application with Qt5(mingw). To run this application out of qtcreator, I have to put some dlls like Qt5Widgets.dll, Qt5Core.dll, ... beside the executable file. I tried to add these libraries to project, but "Add Library" option doesn't accept dll! I can only add static library(*.lib).
I just want to add required dlls to my project and make a *.exe file in output, without any dependency and no any dll around the executable file.
You want to build your application with static linkage. For static linkage you need to compile your Qt with -static option.
How to build static Qt:
For linux: http://doc.qt.io/qt-5/linux-deployment.html
For Windows: I used this guide https://wiki.qt.io/Building_a_static_Qt_for_Windows_using_MinGW
Note: even with static linkage I provide msvcr110.dll and msvcr120.dll with my app, so I have .exe + 2 dlls. But maybe I do some things wrong, but at least I have 3 files instead of tons of it.
I am using Visual Studio 2008 trying to create a .dll. The dll uses an external library (.lib). Compiling and linking works fine (I included the paths to header/lib in the options). When my .dll is used by a program (as a plugin) it says "externalLibrary.dll missing" but there is no externalLibrary.dll, just a externalLibrary.lib.
Are there different options of linking (so the externalLibrary is already in my .dll)? Or can i simply create a .dll from the .lib? Or any other solutions to this problem?
Edit (to be more concrete):
In project properties i added
the header path # C/C++ - General - Additional Include Directories
the library path # Linker - General - Additional Library Directories
the library name # Linker - Input - Additional Dependencies (although
this doesn't change anything)
The .lib file you are using is an import library which basically means that it contains only stubs for functions/classes/... but not the actual implmentation. That implementation is in the dll. An import library is only useful for the linker as it uses it to resolve symbols. But at runtime, the actual compiled code is needed so your application/dll looks for the dll. But even if your dll is used as a plugin, it's no problem for it to depend on other dlls. So if you have the other dll I suggest you go that way. (what is 'externalLibrary' btw?, it's not normal a vendor supplies you only with an import library and not the dll)
If you really do not want to use the external dll, you'll have to find the static library for the code of 'externalLibrary'. Unlike the import library, a static library does contain all symbols complete with actual implementation etc. So after linking with a static library, your application/dll contains the code itself and does not need to resolve it at runtime.
IDE: VS2005
Say I am using Poco library and the executable needs below dlls. I have to put them in same directory where the executable is.
msjava.dll
msvcp80.dll
msvcr80.dll
PocoFoundation.dll
PocoNet.dll
Is there any way that can build a dll-free executable? Thanks.
They don't have to be in the same directory. They can be in another directory if your PATH variables includes the directory they are in.
It looks like the Poco libraries can be downloaded as source, so you should be able to build them as static libraries and make a stand alone executable.
Update
For the msvc DLL's, you can build against static libraries. Bring up the properties of your project, go to C/C++, Code Generation and modify "Runtime Library". Make sure to choose a library other then "Multi-threaded DLL" or "Multi-threaded Debug DLL." You will also want to make sure you do that for the Poco libraries as well.