I'm trying to implement hot reloading for a C++ app that loads a DLL dynamically.
When the app runs (in debug mode), it will copy the DLL and associated PDB to an intermediate directory, and load that.
This is so that in subsequent compiles, the original files can be overwritten.
Since DLLs store the path to their PDB in the DLL header, the app patches the DLL header to point to the correct PDB.
To make sure the DLL size remains exactly the same, I only override 1 character of the PDB name.
When compiling the DLL, I set the PDB path to something like the following (using the /PDBALTPATH linker flag):
Z:/NGEN/Stage/Tmp/TheName._.pdb
Then, when copying the DLL to the Tmp directory, I patch the name to something like:
Z:/NGEN/Stage/Tmp/TheName.a.pdb
Z:/NGEN/Stage/Tmp/TheName.b.pdb
I verified that the DLLs have the correct patched PDB name after copying, using the dumpbin program.
Now, this works fine when I first run the app; the debug symbols are loaded correctly. However, when I rebuild the DLL (in another instance of MSVC) and the app loads the new DLL, MSVC doesn't load the debug symbol of the new DLL.
Instead, I get a message that different versions of the symbols have already been loaded.
Why does MSVC not load the PDB associated with the second DLL?
For your reference: Why does Visual Studio require debugger symbol files to exactly match the binary files that they were built with?
an internal time-stamp will be different. But even disregarding that,
the actual layout of the code could be
different.
I have an EXE application running in debug mode that loads a DLL at runtime.
When I load the dll it automatically loads the dll's debug symbols for it.
But when I call FreeLibrary() on the dll the symbols won't get unloaded.
That is a problem for me because I use cl.exe to rebuild the DLL while the EXE is running so it needs to be freed and unloaded before I rebuild it.
here is the visual studio runtime debug console output when I load and unload the DLL
'Editor.exe' (Win32): Loaded GameAssembly.dll'. Symbols loaded. <--- automatically loads the symbols when I load the dll
'Editor.exe' (Win32): Unloaded GameAssembly.dll' <--- Dosen't unload the symbols (I know so because when I try to rebuild the dll I get the error (LNK1201 error writing to program database 'GameAssembly.pdb'; check for insufficient disk space, invalid path, or insufficient privilege)
and the functions I use to load and free the dll:
m_DLL = LoadLibraryA("GameAssembly.dll");
FreeLibrary((HMODULE)m_DLL);
now I want a way to unload the symbols when I free the dll, Any idea on how it's done ?
The symbols are not loaded in the app itself, they are loaded in Visual Studio's debugger. The good news is that what you are trying to do works just fine as long as you are not debugging the application.
Unfortunately, there is no way to unload symbols from a debugging session (as far as I know).
One way to fix this would be to tell Visual Studio to simply not load those symbols in the first place. You can do that from the modules window. However, this will prevent you from debugging GameAssembly.dll.
So the only alternative is to not be debugging when you rebuild/reload the dll. To do this, you have to create multiple debugging sessions for a single run of your app. Here's how you go about it
Start debugging the application as you normally would.
When you want to rebuild the dll:
Unload the dll
Detach the debugger by using Debug -> Detach All
Rebuild the DLL
Restart debugging the app by using Debug -> Attach to process
Reload the DLL
The order of the steps can be swapped around a bit, of course. As long as you detach before rebuilding, and don't reload the dll until after the build is done, you should be ok.
I'm writing a game (with Angel engine) in Visual C++ Express 2010, and even after commenting out everything in main, the program crashes on startup (the application was unable to start correctly). This started happening after installing VS2012. I have tried restarting, rebuilding, using Release and Debug, running VS as Administrator etc.
Initially I had to put this into the Post-Build Event Command Line to get it to compile:
#echo off
echo Copying $(OutDir)$(TargetName)$(TargetExt) as $(TargetName)D$(TargetExt)
copy /Y $(OutDir)$(TargetName)$(TargetExt) $(OutDir)$(TargetName)D$(TargetExt)
It used to not find the PDB files correctly, but I turned on Microsoft Symbol Servers for the .pdb locations and gave it a cache directory. Now, the Debug output says:
'ClientGame.exe': Loaded 'C:\Windows\SysWOW64\ntdll.dll', Symbols loaded (source information stripped).
with about 20 different dlls, most of which looking like standard windows things, and opengl. A few don't have "source information stripped" after them. A few say this:
'ClientGame.exe': Loaded 'C:\Windows\SysWOW64\devil.dll', Binary was not built with debug information
In Solution output, I get:
directorytoproject\Libraries\libogg- 1.3.0\win32\VS2008\libogg_static.vcxproj : warning : Platform 'x64' referenced in the project file '_libogg' cannot be found. Please make sure you have it installed under '%VCTargetsPath%\Platforms\x64'.
with a couple of other libraries as well.
Runtime library setting is on "Multi-threaded Debug DLL (/MDd)"
I would really appreciate any ideas! Thanks a lot!
A question about pdb file. Is pdb file for debugging in Visual Studio? If so, why do they also exist in my Release folder? It's normal that pdb files are in Debug folder, but why they are also in Release folder.
So I have now a Release folder build by Integration team with all the pdb files. Now I can load all the corresponding source (in GIT) so I'm sure that the binaries correspond to the source. Then do I need to build again in order to debug in Visual Studio? If not, what I have to do in order to get thing done quickly?
As mentioned above, PDBs are as much important as release binaries! Once a software is released, you can debug it afterwards (depending on whether public and private symbols are available). Should the PDBs contain private symbols, please keep in mind that these describe your code (parameters, types, return values, symbols...). Here an article explaining the logical link that exists between an executable and its PDBs.
Actually you can debug your release build too - if you have the PDB files. So it's a good idea to keep the PDB files of your shipped product (release build).
For debugging you need the executable and the matching PDB and the matching source files. That's it.
You can debug a release build as well, it's just that it's not that useful because of all the extra optimizations. If you don't want a pdb file, you can specify it in the project properties for the release build.
Is pdb file for debugging in Visual Studio?
YES.
why do they also exist in my Release folder?
Go to "your project" Property Page (target release) -> Linker -> Debugging.
Set the option Generate Program Database File. i.e. Release/myExe.pdb
I copied an existing project and renamed the folder. Now I get this error when I try to compile the application
debugging information cannot be found or does not match. No symbols loaded.
Do you want to continue debugging ?
If I click yes, it compiles and runs fine. But now I have to deal with that message. Just curious about what I change in the projects properties to get it to stop.
You probably have deactivated the debugging information for your project:
Right click on your project -> Properties
Configuration properties -> Linker -> Debugging
Switch "Generate Debug Info" from No to Yes
Rebuild your project and retry, it should now run without the message :)
The main reason is that you don't have a matching pdb and exe.
Some possible solutions:
You are compiling in release instead of debug
You need to clean/build or rebuild
You don't have your pdb files being generated in the same directory as the exe
You have a mismatching pdb, maybe the copied source is newer than today's date and something isn't building properly.
Try cleaning out all debug object files
You are attaching to a process that you started from a different location from where your build exe and pdb exist
Restart Visual Studio
This happens to me every now and then, while debugging code and making changes it seems like visual studio caches the pdb information and sometimes it gets stuck. Doing a Rebuild solution, deleting the pdb and creating a new one doesn't fix the problem.
Of course I do have the generate debug information on and all that it's needed, specially since this happens while debugging the code several times.
Visual Studio seems to be happy with the in-memory pdb and refuses to update it, regardless of time-stamps or even size changes in the pdb.
The only way to reset this is to exit Visual Studio (the IDE) and restart it again.
In some rare occurrences, the IDE might be still running in the background (process explorer shows it there) and might hold the handle to the file open. You can kill the process before restarting the IDE.
Good Luck
I just encountered this error in VS2012. It is definitely caused by a bug in Visual Studio, which reveals itself in situations when the local PDB file of the main project has the same name as the final PDB file for the entire executable (even if the two are located in different directories!)
Consider this example.
Solution consists of three projects: main, a, and b. main is the top-level project for the executable, while a and b are libraries linked into main.
In all three projects $(IntDir) variable is set to $(SolutionDir)\$(Configuration)\$(ProjectName)\. This means that project main dumps its intermediate files to Debug\main\, project a - to Debug\a\ and so on.
In C/C++ -> Output Files settings all three projects have Program Database File Name value set to $(IntDir)$(TargetName).pdb. This means that project main generates its local PDB file as Debug\main\main.pdb, project b as Debug\b\b.pdb and so on.
Finally, in Linker -> Debugging settings of project main the Generate Program Database File value is set to $(OutDir)$(TargetName).pdb. This means that the global PDB file for the entire executable will be generated as Debug\main.pdb.
Note that in this setup each PDB file is generated in its own, separate directory.
In this setup you will get Debugging information cannot be found or does not match error if you attempt to run the program under the debugger. And if you take a look at the Debug\main.pdb file (which will exist), you will notice that it is exactly the same as Debug\main\main.pdb file! I.e. somehow the local PDB for main managed to overwrite what was supposed to be the global PDB for the final executable. I.e. the debugger is right to complain that the PDB file is "wrong". It is indeed wrong.
Again, in the above setup the final global PDB somehow gets overwritten by local PDB of the top project. I don't know why it happens. It appears to be a bug. (Note that even though these PDB files have the same name, they are generated in different directories, i.e. they should not conflict.)
A workaround that fixes this issue is to give the local PDB of project main a different name. For example, just go to C/C++ -> Output Files for the main project and change Program Database File Name value to $(IntDir)$(TargetName)_local.pdb (or to $(IntDir)12345.pdb if you so desire). This will eliminate the conflict and solve the problem.
Enable PDB creation by:
Right click on MyProject > Properties > Debugging:
C/C++ > General > Debug Information Output = Program Database (/Zi)
Linker > Debugging > Generate Debug Info = Yes (/DEBUG)
Clean MyProject, restart Visual Studio (just to be sure), rebuild MyProject.
The output folder should then contain *.pdb files.
If you debug optimized/release code consider switching off optimization via
C++ > Optimization > Optmization = Disabled (/Od)
I faced the same problem and tried all above mentioned solutions but it couldn't help me.
Then I found a new solution randomly and it worked.
Solution is that,in case you are having many projects in a solution then you should mark any one (specific one which you have to decide) project as a "Set as Startup Project".
Right click on that specific project and click "Set as Startup Project".
It worked for me.
The pdb or Program Database file appears to be missing (basically, the path has changed and can no longer be found by the compiler). See this related post for additional information.
I had a similar problem and the reason was that I had run one of the projects of my solution in a different process and that process couldn't be killed. I didn't think much of it. So when I was building the solution in a separate environment one of the pdb files didn't match so at the end I couldn't load any of the pdb files. I just restarted my computer and that fixed it.
Good luck
Restarting Visual Studio can fix one instance of this problem.
Right click on your project in the solution browser => Clean => Build.
That is if your build generates a .pdb at all (look in your target dir)
If not, you should enable debug by the steps mentioned in other posts
Most probably there are other reasons like .pdb / .exe file mismatch, something were not built / rebuilt, but I had similar case in Visual studio 2013 -
Something to do with virtual inline function - so I suspect.
In my case debugger were jumping in a middle of another C++ function, not the one which was called. Jump was off source code by 11 source code lines, but I cannot explain why much miscalculation happened. By simple rearranging functions I've got rid of this problem.
May be needs more detailed analysis why 11 lines shift happened originally.
Haven't seen this kind of behavior in any other visual studio.
This problem has bothered me for a long time. AnT's anwser is very helpful. The main idea is Don't have any two pdb files have the same name, even they are not in the same directory.
This is my situation: I have tow projects name "FooBar" and "FooBarDll", the first one is an exe, and the second one is a dll. I set both projects Target Name to be "FooBar", so that they will generate "FooBar.exe" and "FooBar.dll" respectively.
Then I set
"General -> Intermediate Directory" to be "$(OutDir)\$(ProjectName)\"
"C/C++ -> Output Files -> Program Database File Name" to be "$(IntDir)$(TargetName).pdb"
"Linker -> Debugging -> Generate Program Database File" to be "$(OutDir)$(TargetName).pdb"
So I get these files:
Debug\FooBar.exe
Debug\FooBar.pdb //C++ pdb
Debug\FooBar\FooBar.pdb //Linker pdb
Debug\FooBar.dll
Debug\FooBar.pdb // C++ pdb again!
Debug\FooBarDll\FooBar.pdb // Linker pdb
My solution is replacing every "TargetName" with "ProjectName", then I will get:
Debug\FooBar.exe
Debug\FooBar.pdb //C++ pdb
Debug\FooBar\FooBar.pdb //Linker pdb
Debug\FooBar.dll
Debug\FooBarDll.pdb // C++ pdb
Debug\FooBarDll\FooBarDll.pdb // Linker pdb
Then there is no conflict!
Give C/C++ pdb a suffix may be better, like: "C/C++ -> Output Files -> Program Database File Name" to be "$(IntDir)$(ProjectName)_C.pdb"
I had the same issue, and this link helped me solved the problem, by rename "symsrv.no" to "symsrv.yes" in VS IDE folder.
Curious, it happens to me that I needed to change the folder name from:
...\Custom Librarry (MyDll.dll(
to
...\Custom Librarry (MyDll.dll)
just by closing the parenthesis it worked !