I'm new to the world of .NET and I'm trying to understand the build process. If the concept of DLLs is to resolve references at run time why does visual studio need to to know about DLLs at compile time in order to build an executable ? Can't seem to find a definitive answer anywhere.
DLLs are loaded at runtime so your code can call code in that DLL, indeed. However, they are also needed at compile time so you can write code calling into that library.
Back in C++ I think that was done with .lib files or via COM, so the compiler didn't actually need the DLL. In .NET that's different because the DLL contains the code to run and the interface so other programs can use it.
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I have a legacy project that used to be build in Visual C++ 2005 Express, and it depends on a certain third party DLL. As far as I can tell it doesn't come with a lib or header file.
The project compiles fine in Visual C++ 2005, here is a screenshot showing the DLL visible and browsable in the object explorer. The code can also use it without #include or anything like that, which is pretty weird.
Importing the project into Visual Studio 2019 works as well, the code can still use the DLL and it is listed under both the dependencies and the references:
I now want to achieve the same thing in a new project, but I cannot figure out how to register the DLL as a dependency. Things I found online and tried:
"Just include the header or lib file" doesn't work, I don't have one
LoadLibrary() and GetProcAddress() are awfully contrived and don't seem necessary because it's clearly possible without.
Create your own lib file doesn't work either, dumpbin doesn't show any symbols for my DLL: image
How do I register the DLL as a dependency? And where does Visual C++ 2005 get the list of methods in the DLL from is the first place?
I wrote a tool that many users would use on their computers. I noticed however, that users who do not have visual studio installed, cannot open my executable. The error says that msvcp100.dll is missing. I found in internet a redistributable package from microsoft, that should apparently provide these dlls. My question is: is there another way to bypass this problem? Something like an option in the project properties?
Yes, you can change a compiler setting to link the C++ standard library classes into your program instead of having a dependency on the DLL. Right-click your project in the Solution Explorer window, Properties. Switch to the Release configuration (upper left). C/C++, Code Generation, Runtime Library setting. Select /MT.
Only do this when you only have a single monolithic EXE. When you use your own DLLs then you really need msvcr100.dll and msvcp100.dll so that the runtime library gets shared between all modules.
It is part of C++ runtime and the target machine needs it. THere are couple of ways to address it.
Please check following link from Microsoft MCVCP100.DLL
I have a C# 4.0 application that is referencing a type library from a C++ application. This is used for some secure COM interop, a question I originally had asked here.
On my development machine this second application is installed so I can compile without any issues. If I attempt to compile on our automated build server, or any machine with Visual Studio installed but without this second program, I receive the following errors and compilation fails:
Text for google:
The type or namespace name could not be found (are you missing a using directive or an assembly reference?)
Cannot get the file path for type library "guid...." version 1.0. Library not registered. (Exception from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED))
The referenced component 'SecurityAgentLib' could not be found
Picture for readability:
I'm not sure how to get around this other than by installing the application that registers the actual dll that implements these types, but I don't want to do that on our build server. The code that uses these types are wrapped in a class that is never instantiated unless prerequisite checks are run to verify the app is actually installed, so there is no chance of a runtime error. In fact I can run my app just fine on a machine without the second app installed - I just can't compile it there.
In visual studio the reference points to the .tlb file which is included in the solution directory, so the tlb file itself is present.
I can't imagine it should work this way, and I've searched around, but I'm apparently not searching for the right terms.
EDIT:
Running tlbimp.exe generates a dll but the type library should be sufficient for compilation, I thought at least. There is also an issue of broken references. I was reading this article Troubleshooting Broken References and it says that if the reference was to a COM component that is not installed than installing the component corrects the error, which is true.
Installing it on the build server really isn't an option. Opening visual studio and re-adding a reference if the path was broken doesn't work either.
I was able to use tlbimp to create a dll and used visual studio add a reference to that dll. That let me compile, but how would this work in an unattended build server?
EDIT
Okay I came up with two solutions that worked given my requirement of this all being unattended
Ran tlbimp to create a dll from the type library. I removed the reference to the tlb from my project and added a reference to the dll itself. When the source code was copied over to a new computer it compiled without issues.
In this scenario ideally we would checkout from SVN on the build server and copy the latest DLL from the second project, then compile this project.
I also removed the tlb and added the dll in visual studio and did a diff on the .csproj file. I don't see any downside to just having a reference to the dll instead of the tlb but if needed the build server could make modifications directly to this file to remove the tlb section and add a reference to the dll following a build of the second product.
Here are a couple options that each worked.
Ran tlbimp to create a dll from the type library. I removed the reference to the tlb from my project and added a reference to the dll itself. When the source code was copied over to a new computer it compiled without issues.
In this scenario ideally we would checkout from SVN on the build server and copy the latest DLL from the second project, then compile this project.
I also removed the tlb and added the dll and did a diff on the .csproj file. I don't see any downside to just having a reference to the dll instead of the tlb but the build server could make modifications directly to this file to remove the tlb
I have a C++ dll. Is there a way to compile it so that it can be used with VS2005/2008/2010 instead of me having to do 3 different builds?
Thanks
You can generally "use" a C++ dll with any version of Visual Studio, if you're just linking to it.
However, when your dll is compiled, it will be targetted to a specific version of the C++ runtime, so end-users of your program will need to have that runtime (Visual C++ redistributable package) installed on their PC. So if you use a dll built by VS2005 and an exe built by VS2010, your end user will have to install both the 2005 and 2010 redistributable packages. The same generally goes for other libraries if you use them (MFC, etc)
If you do this, you will also have to be careful about memory allocation - memory allocated in one runtime version cannot be safely deallocated by another. So anything that your dll allocates must also be deallocated by the dll, and anything allocated by your exe must not be deallocated by the dll.
As a result, most people will rebuild the dll with the same version of VS as they build the rest of their program in, to minimise the compatibility issues - ultimately it's much easier to build in each verison of VS than to sort out all the issues involved in not doing so.
(Hint: You can run VS from the command line and get it to build a project/solution, so it's a 5 minute job to write a batch script that will automate building all three variants in one go)
The version of visual studio in use doesn't make a difference as to whether a given assembly can be referenced.
The only thing that matters is what version of the framework the assembly was compiled against.. Assuming it's a .net assembly anyway.
Regardless, it's common practice to provide versions compiled against each framework rev (2.0, 3.5, and 4.0) anyway.
However, if you are compiling an unmanaged c++ dll; then just provide a 32 bit and a 64 bit version of that dll. In this case the .net version in use (and visual studio version for that matter) is immaterial.
I have a communication library built on top of Qt and Google Protocol Buffers. It's currently being built with MinGW/GCC on Windows. My goal is to use the same library in C# on .NET, with the help of a thin wrapper on top using C++/CLI (bridging the unmanaged code with managed code).
I tried using the MinGW produced DLL directly in my C++/CLI project, but I keep getting linker errors (cant remember the error codes right now, but something about missing tokens and functions/signatures).
First question is: Should I be able to use the MinGW-produced DLL with the Visual Studio compiler/linker? Or do I need to compile the library again, using only VS compiler for all projects?
If I should be able to use the MinGW-produced DLL directly, how do I reference it in Visual Studio 2010? In project settings it seems to look for *.lib files, but I can't find any .lib files in the output of MinGW/GCC. It does produce *.a files, but it seems like Visual Studio don't handle this kind of file..
I should also mention that both Qt and protobuf are also compiled with MinGW. But I can of course recompile all the parts in VS 2010 if necessary.. Would have been nice to save the recompile time though, since our buildserver already has a working setup using MinGW.
The easiest way to use it would be by recompiling it with Visual Studio. This is when I am assuming C++ types and classes used in the interface you intend to use.
In case you have a C interface to this library you could dynamically load the library via LoadLibrary and use GetProcAddress to access those functions.
However it depends completly on the way how you intend to use the library.