Producing a hybrid static library with MSVC

Question

It is my understanding that Visual Studio library projects use two separate processes after compiling, depending on the "General/Configuration type" setting:

• If "static library" is selected, all of the object files are bundled together into the final .lib file, a static library.

• If "dynamic library" is selected, all of the object files are linked together, along with dependencies, and bundled into the final .dll file, a dynamic library. Meanwhile, all of the __declspec(dllexport) symbols are gathered, and used to generate a .lib file, the import library.

I would like to create a foo.lib/foo.dll pair, where foo.lib is both an import library for foo.dll and a static library on its own. I have considered the following leads:

• Create two separate projects, FooLib and FooDll, and use lib.exe in a post-build step to merge both .lib files. This sounds like the easiest option but requires splitting in half what should otherwise be a cohesive module.

• Create a single DLL project, let the default build process create foo.dll and its import library. Then add custom build steps to manually gather the object files and bundle them into the import library with lib. This sounds messy, and I'm not sure what the duplicates will do.

• I've tried messing around with .def files, but even after dumpbining the resulting lib files I'm a bit perplexed by its behaviour. Also, it needs an explicit list of mangled symbols, which is impractical.

Is there a simpler way to achieve that hybrid .lib/.dll combo? Otherwise, which lead should I rather follow?

---

Background

This module will be used in several .dlls and one .exe linked together. I need to have a single instance of half of its data in the resulting process at runtime (which is achieved by the .dll, since it will be only loaded once), while the other half is duplicated into each .dll or exe and initialized therein (which is achieved by the .lib).

Answer 1

I have finally taken the first route I listed in the question: create two projects, a static library and a dynamic library, and merge their outputs. This ended up being easier than expected: I just had to register the DLL's import library as a dependency for the static library's "Librarian" build step, and setup a project reference to have the correct build order.

FooDll.vcxproj:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <!-- snip snip snip -->
    <PropertyGroup>
        <TargetName>Foo</TargetName>
    </PropertyGroup>
    <ItemDefinitionGroup>
        <Link>
            <ImportLibrary>$(OutDir)FooDll.lib</ImportLibrary>
        </Link>
    </ItemDefinitionGroup>
    <!-- snip snip -->
</Project>

Foo.vcxproj:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <!-- snip snip snip -->
    <ItemDefinitionGroup>
        <Lib>
            <AdditionalDependencies>$(OutDir)FooDll.lib;$(AdditionalDependencies)</AdditionalDependencies>
        </Lib>
    </ItemDefinitionGroup>
    <!-- snip snip -->
    <ItemGroup>
        <ProjectReference Include="..\FooDll\FooDll.vcxproj" />
    </ItemGroup>
    <!-- snip -->
</Project>

The end result is a Foo.dll/Foo.lib pair, the latter being both a static library on its own and an import library for Foo.dll.

I still have to straddle two projects, but this is simple enough that I'm happy with it.

Answer 2

To the best of my knowledge you cannot create a single .lib for this, however you can use msvc's #pragma comment(lib, ) to achieve much the same thing, you simply have more than one #pragma comment(lib, ) one for the dynamic .lib and one for the static.