I have a project that imports a DLL (written by me). Sometimes when an exception is raised within a method in the DLL, the host project opens a tab and let me see the code within the DLL. I can also put breakpoints within it.
But this behavior seems quite random, I cannot have it on purpose and not always works. Plus, I can't see the file name in the project explorer window.
Any help on debugging DLLs? Thanks
The enhanced debugging (for a dll not in the current solution) depends largely on whether you have the debugging symbols file (.pdb) in an obvious location - in particular, next to the dll itself. You can also load symbols manually from the modules window (when debugging, Debug -> Windows -> Module, right-click, Load Symbols From...)
What may be getting in your way here is a feature known as Just My Code (JMC). This is a debugger / CLR feature designed at limiting a users view of the world to just the code that they've written. The various ways in how a piece of code or DLL is determined to be yours or not can be confusing at times.
Next time you hit this problem, try disabling JMC and see if it fixes your problem
Navigate: Tools -> Options
Navigate: Debugger -> General
Uncheck the Just My Code option
On the managed C# program that calls the C++ dll,
right-click properties
debug tab
Tick Enable unmanaged code debugging
Hope this helps,
Tony.
To debug a dll it must have the pdb file with the debugging information that matches that dll.
Visual studio uses the .Pdb symbols generated by the compile process to enable you the dev to peek at the source when an exception occurs.
This information exists for two reasons. The first reason is for the compiler (i.e., a program that turns source code into an application, such as an .exe or .dll file) to use when it builds the application. The second reason is for people to use when debugging an application. The symbolic information is generated as part of the compilation of an application (if you set the compiler to generate symbolic information). This information can reside directly in the application files, or it can be written to separate symbol files. Where the symbols reside depends on your development application and the settings you choose. For example, Microsoft Visual Basic (VB) builds symbols right into the program files. Visual C++ (VC++) usually builds one or two separate files.
Symbol files have two file types—.dbg and .pdb. The .dbg files are in Common Object File Format (COFF), which is a generic symbol file description that doesn't include source line information; many debuggers can read these files. The .pdb files are a Microsoft format and contain a lot more information than the .dbg files. For example, source line information is available only in .pdb symbols. Symbol files that include source-code line information let you use the source code for debugging.
While it doesn't allow you to debug the code, Reflector is very useful when it comes to inspecting a DLL. The combination of a Stack Trace, the offending DLL and reflector will often get you to the nub of the problem.
Related
There is a c# Application that compiles C# code stored in DB and creates a DLL in memory using roslyn compiler that the DLL is loaded in memory and an instance of the type is created from the following code
Activator.CreateInstance(type); // Just creates an instance of the type so that any public method or property can be accessed
The reason for having the code in DB is abit complex to explain here for the scope of the question but it is important to note there is no physical file where C# code is present.
Also please note the DLL is created at runtime by the application in release mode or debug mode depending if #ifdebug is true or not.
Now what we want is if the application is running in debug mode we should be able to debug the DLL created in runtime. Can experts over here help me to give pointers how to achieve it. Since access to code is there from DB we can in runtime create a temporary file in some temporary location if the application is running in debug mode but how do we let Visual studio know we want to link the specific DLL to this temporary C# file for the purpose of debugging. Please note the DLL is in memory in some concurrent bag and we arent creating PDB file too
Any pointers will be helpful We are using Visual studio 2022
This is possible in Visual Studio 2022!
Follow the guidance of emitting the portable PDB from this answer. Since you didn't show much of how you are compiling, I will assume it's pretty close to that and getting the source code emitted won't be a problem.
When the assembly is finally loaded into the program, VS2022 will automatically pick up the symbols. You can verify this by looking for a your named DLL in the Modules window. Ctrl+Alt+U or Tools>Windows>Modules. From the answer I posted, it will be randomly named.
When you have the program running, the external sources node (which is new with VS2022) will show that same random DLL name.
If you open the generated file, you should see your generated code. You are also able to place breakpoints in this file!
Not sure if it matters or not, but in my VS options I have disabled "Just My Code".
I'm not sure if this is possible with Visiual Studio but maybe you could have some luck with dnSpy:
https://github.com/dnSpy/dnSpy
I was able to debug a dll that was loaded by a program at runtime using:
System.Runtime.Loader.AssemblyLoadContext.Default.LoadFromAssemblyPath(path);
so maybe it can help you too.
In my application i am using the third party dll and i dont have any soruce code avialable.
Now i am getting the exception in Windows7 OS, so i would like to debug and kwow what is the exact reason.
Reflector will not help me in this case as its a unmanaged dll. And decompiler is giving error on passing this dll(Extraction of source code).
To debug in visual studio, it expects the PDB file and .pdb can be generated only from source code.
In the debug section i slected "Enable Native code debugging option" and in security section i selected the option as paritially trusted application to get rid of the exception.
I am not able to conclude, what could be the problem and dont have any idea apart from above, how to resolve?
On my knowlege we can not debug unmanaged dll, if we dont have source code available.
Can any one please suggest, if we have any techniques around that.
My thought process: If i can get runtime information on which API its failing, i could opt for alternative API and resolve the problem.
Thanks in advance.
Regards,
Siva.
Of course you can debug it. You can step through assembly code just fine and check the state of registers, etc.
It seems that you really want to debug by inspecting and executing the original source code. This is obviously impossible without the source code, as it is in general not possible to reverse engineer the source code from optimized native executable (it is possible to reverse engineer functionally equivalent code, but this can differ heavily from the original source). Native dll usually doesn't contain names of the symbols (classes, functions, members, etc) except for the exported ones, so it is not possible to create e.g. a friendly stack trace with method names.
Besides that, even if you had source code, it would be useless without symbol file (.pdb), as pdb contains data about mapping between original source code and compiled instructions, as well as other information (symbol names, optimization info, etc).
However, it is not that hard to debug using assembly code if you have a pdb file but not the source code (ok, it is not that easy, either :). These 2 articles (http://www.microsoft.com/msj/0298/hood0298.aspx and http://www.microsoft.com/msj/0698/hood0698.aspx) have enough info to debug most of the usual situations where you might need that.
I'm trying to re-jig the layout of a very large solution which has become impossibly hard (and s l o w) to work with. My plan is to create a number of solutions containing related projects, and then use binary references where necessary to link to libraries produced by the other solutions.
The thing we rely on to make this usable is Resharper's Navigate to External Sources functionality, so we can easily browse the source of the projects we are referencing from other solutions. Quite why VS can't do this out of the box is beyond me.
This is all working very nicely for classes with implementation. However, for C# interfaces and classes containing only auto-implemented properties, Resharper isn't able to browse to the sources, and falls back to cruddy metadata viewer.
I used srctool.exe, which comes with the Symbol Server tools in MS Debugging Tools For Windows, to browse the sources listed in the .pdb file, and it's clear that the sources for these interfaces and empty(ish) classes are not referenced in the pdb file. If I switch the auto-implemented properties to those with backing fields, then the source link appears in the pdb.
I'm guessing the sources are excluded because there are no places you could set breakpoints on interfaces and auto-implemented properties.
I'm wondering, though, if there is some exotic compiler option or workaround we can employ to force the PDB file to include references to the source of C# interfaces.
Thanks,
Mark
The question doesn't have enough detail. Shooting off the hip, I'd guess that you tackled the problems with the slow massive solution by converting project references to assembly references. And used the Release build of those projects as the reference.
And yes, that stumps any tool that tries to find source code files from the PDB. The release build of a .NET project uses a stripped version of the PDB, all the source code file and line number info has been removed from it. That's a pretty normal thing to do with real release builds. Release built code normally is optimized. That causes code to be re-ordered, no longer matching the logical position of the code in the source file. Any info you get from the source+line PDB info now tends to get between harmful and useless, you start looking in the wrong place for a problem.
That is however not a concern for IDE tooling or while debugging your app. The optimizer is automatically disabled in a case like this. Actually a configuration item in VS: Tools + Options, Debugging, General, "Suppress JIT optimization on module load" option. Turned on by default.
Clearly any tooling that uses the PDB is going to catatonic when they don't have a chance to find source files. The fix is to go back to the original project, select the Release configuration again and change a setting: Project + Properties, Build tab, scroll down, Advanced button. Change the "Debug info" combo from "pdb-only" to "full". Rebuild the project.
Should fix your problem. Also revives the debugger, you can step into the source code again.
Don't move files around too much btw, you might stump the chumps again. At least keep the PDB with the DLL in the same directory. If the source code is no longer present in the same directory but you checked it out again in another one then you have to tell the IDE about it. Right-click the solution, Properties, Debug Source Files setting.
I’m writing some logic for academic purposes symbol source server.
I have to check assembly and its pdb file if they match each other so users could use them without any problems.
I’ve made little research, but without anything spectacular. If VS will get wrong symbols debugging it might show information:
The following module was built either
with optimizations enabled or without
debug information:
assembly.dll
To
debug this module, change its project
build configuration to Debug mode. To
suppress this message, disable the
'Warn if no user code on launch'
debugger option.
I’m also wondering what information VS gets from pdb and assembly to validate them.
Is there any (managed) API? Or even unmanaged?
Any ideas?
This page contains an excellent article on the gory details of PDB and DBG files. It explains exactly what is stored in a symbol file, how to read it, and how to determine whether the binary file (EXE or DLL) and the symbol file (PDB or DBG) match.
http://www.debuginfo.com/articles/debuginfomatch.html#details
I think the name of the API Visual Studio uses is DIA; it's a COM API that you can call from C#.
The Mono.Cecil library provides a nice set of classes for accessing assemblies and their symbols; it uses DIA underneath for .pdb files. I would call Cecil directly for this; if not, the source code should provide a guide.
My project has several new C# modules and one C module (not C++) compiled using win32 system calls. I'm using the PInvoke interop layer to call the C code from the C#. The C function is getting called.
All modules are writing to a single bin directory and all write pdb files.
On running, and then stopping at a breakpoint right before a call into the C.dll, I see the breakpoints in the C module are disabled. Looking at the Debug|Windows|Modules list I don't see the C.dll module loaded even after the call has been executed.
One more factoid: in Solution|Properties|Configuration Properties|Configuration is shows the C# modules using Platform = "Any CPU" and the C module using "Win32"
Why isn't the module loaded and why aren't its symbols loading?
Thanks,
Max
I've consolidated answers from several sources.
Are you running the debug configuration?
In the Solution check: SolnExplorer|Solution|Properties|ConfigurationProperties| Configuration = Debug
and: SolnExplorer|Solution|Properties|ConfigurationProperties| Configuration|ProjectConfig[]=Debug
-->Note:Although breakpoints will work with release configuration, sometimes the lines may be optimized out or rearranged.
Are you generating debug information?
In C# projects: SolnExplorer|Project|Properties|ConfigurationProperties|Linker|Debugging|Generate Debug Info=YES
In C++ projects: SolnExplorer|Project|Properties|ConfigurationProperties|C/C++|Debug Information Format = Program Database(/Zi)
-->Note: It pays to check the command line arguments.
Is everything is being rebuilt? If the PDB is out of sync, the debugger may not be able to load symbols:
In Solution: SolnExplorer|Solution|Properties|Configuration Properties|Build=TRUE(Checked) for all projects.
Can you debug unmanaged code?
In C# projects: SolnExplorer|Project|Properties|Debug|Enable unmanaged code debugging = TRUE(Checked)
In C/C++ projects: SolnExplorer|Properties|Configuration Properties|Debugging|Debugger Type = Mixed
Are files being put where you think they are? I use a single bin\debug directory for collecting all project DLL's and PDB's.
In the C# projects: SolnExplorer|Project|Properties|Build|Output Path = ..\bin\debug
In C/C++ projects: SolnExplorer|Project|Properties|ConfigProp|Linker|OutputFile = ..\bin\debug\$(TargetName)$(TargetExt)
Are old files getting in the way?
Check the timestamps on all the output files in the bin directory. Make sure they are as of the last rebuild.
Some people advise blowing away all the bin and obj directories. This may be worthwhile just to see that old files aren't laying about. Checking the time and date stamps should do just as well.
Has the DLL been loaded? If the Breakpoints are disabled, it may be because the DLL has not been loaded yet.
Check Menu|Debug|Windows|Modules.
Look for the dlls in the module name.
In the same Modules window make sure files are loading from the correct path.
If an assembly is shared among several programs, it can be loaded from the GAC.
-->Note: You can preload the C/C++ DLL before it is required. Use: IntPtr lpDLL = LoadLibrary(myLibraryName);
I have a Windows Service in C# with a C++ DLL. The problem I saw was what Max noted:
The DLL worked, but never showed up in the Modules window.
I have done a lot of searching and this is a nice list which matches with information from many other sources.
To make ikh's note explicit:
"Auto" did not work for me, but explicitly setting "Native" and
"Managed" code in the Attach dialog worked.
Here is my fifty cent. In my case it appeared that the pdb files of my c++/cli projects were not updated anymore, while the pdb files of my c# projects were.
This probably rendered them invalid and made the debugger fail to load them.
I remembered to have moved the source base of my project. After a little bit of grepping it occurred to me that some absolute path issue might be the problem. Running a git clean -dfx solved the problem for me.