Sharing Precompiled Headers Between Projects in Visual Studio

Sharing precompiled headers between projects in Visual Studio

Yes it is possible and I can assure you, the time savings are significant. When you compile your PCH, you have to copy the .pdb and .idb files from the project that is creating the PCH file. In my case, I have a simple two file project that is creating a PCH file. The header will be your PCH header and the source will be told to create the PCH under project settings - this is similar to what you would do normally in any project. As you mentioned, you have to have the same compile settings for each configuration otherwise a discrepancy will arise and the compiler will complain.

Copying the above mentioned files every time there is a rebuild or every time the PCH is recompiled is going to be a pain, so we will automate it. To automate copying, perform a pre-build event where the above mentioned files are copied over to the appropriate directory. For example, if you are compiling Debug and Release builds of your PCH, copy the files from Debug of your PCH project over to your dependent project's Debug. So a copy command would look like this

copy PchPath\Debug*.pdb Debug\ /-Y

Note the /-Y at the end. After the first build, each subsequent build is incrementally compiled, therefore if you replace the files again, Visual Studio will complain about corrupted symbols. If they do get corrupted, you can always perform a rebuild, which will copy the files again (this time it won't skip them as they no longer exist - the cleanup deletes the files).

I hope this helps. It took me quite some time to be able to do this, but it was worth it. I have several projects that depend on one big framework, and the PCH needs to be compiled only once. All the dependent projects now compile very quickly.

EDIT: Along with several other people, I have tested this under VS2010
and VS2012 and it does appear to work properly.

Visual Studio deletes a shared .pch file, and questions about custom build steps

For some reason (I did this or not) the generated by compiler .pdb file was not $(PlatformToolsetVersion).pdb, but $(ProjectName).pdb . So the copied into other project folders shared .pdb file was pch.pdb in my case, while other projects were expecting different names. And that was triggering a DELETE task in Microsoft.CppCommon.targets , ("Delete the pch file if the pdb file has been deleted."). Instead of changing the output .pdb name I just looked into XCOPY command and made it to change the copied filename to an expected by a specific project (actually then I just added a custom Target with a renaming Copy task right into the project file instead of using the CustomBuildStep calling a xcopy OS's command, as now I learned more about MSBuild).

Then I also changed the generated by Linker output .pdb, just added "Linked" suffix to the name, so there are no conflicts between Compiler's and Linker's PDBs. Not sure if that is a good idea to change the default settings without a big reason.

I guess it's better just to change the Compiler's output PDB to $(PlatformToolsetVersion).pdb , so all projects will use the same name.

That was the first time I had looked into MSBuild and advanced project settings, now it seems to be obvious, that a project using a shared .pdb wants some familiar .pdb name, not a random pch.pdb

Here is my custom Target imported into project files copying the shared .pdb only if it was rebuilt (.idb is not generated in my case):

<Target Name="CopyFreshPchPdb" BeforeTargets="ClCompile" 
    Inputs="$(PchDir)\pch.pdb"
    Outputs="$(IntDir)\$(ProjectName).pdb">
    <Message  Importance="High" Text="Copying shared pch.pdb" />
    <Copy
        SourceFiles="$(PchDir)\pch.pdb"
        DestinationFiles="$(IntDir)\$(ProjectName).pdb">
    </Copy>
</Target>

Unable to use Precompiled headers in visual studio

Okay I've fixed the problem. when I was including b5pch.h in my cpp files I was doing it like this:
#include ../b5pch.h since they were in different directories.
When I moved pch files in same directory and I just wrote #include b5pch.h there were no more errors. I didn't wanted them to be in same folder so I've moved them back out but in Project Properties->Additional Include Directories I've added "src" so I could just use #include b5pch.h in my cpp files even tho they were not in the same folder.

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