拆分一个Visual Studio C ++项目：如何（几乎）自动做到？

Question

I have a Visual studio 2015 C++ project that has references to a few 3rd-party free library.

Just to reduce compile time (currently 5 - 90 seconds),
I want to split the project into many smaller projects.

In preparation, I have already created filters in the solution explorer.
The filters show a top-level structure of my project - divided into tier :-

Tier 1  - my core library, no reference to outside, rarely change
Tier 2a - my custom encapsulator for external library "A"
Tier 2b - my custom encapsulator for external library "B"
...
    note: all Tier2 #include Tier1 , rarely change
Tier 3  - business logic that rarely change, #include Tier1&2
Tier 4  - business logic that often change , #include Tier1&2&3

Question : How to split this project into many projects easily?
eg almost easy as click a filter then select "extracted to a new project"

I have read some sources - their explanation suitable for how to create from scratch, not for an existing project.

It also seems that I have to add some lines for some individual files.

#if defined DLL_EXPORT
#define DECLDIR __declspec(dllexport)
#else
#define DECLDIR __declspec(dllimport)
#endif

I have >100 files, so it is not very practical.
I googled "split visual studio c++ project", but did not find many results.

Relate question : not explain "how"
How do you split a Visual Studio Solution?

External link : all has the line #define DECLDIR __declspec(dllexport)
http://www.codeguru.com/cpp/cpp/cpp_mfc/tutorials/article.php/c9855/DLL-Tutorial-For-Beginners.htm
https://manski.net/2011/11/creating-a-dll-project/

Answer 1

I would like to note first that if your lower tiers rarely change, whole compilation would rarely occur too. Also note that there is no one click to rule them all solution.

You're almost there. If you've already grouped your project into separate library, the next step would be to actually turn them into dynamic library. This would speed up compilation greatly as long as no symbol are changed (implementation modification is fine). For example for Tier 1 project:

First, create a dynamic library project (DLL Project). Erase all source code which generated by VS. Group all Tier 1 's source code (header and cpp/implementation file) to the project's directory. Add them to the project.

We can have multiple dynamic libraries for each header file, but Visual Studio is not the best IDE for such task (use technology like CMake or QBS). To be safe, consolidate declarations into single header file (or at least some manageable number, don't forget to change the #include in implementation files). Add dynamic library macro to the header, eg tier1lib.h

#ifdef DLL_EXPORT
#define DECLDIR __declspec(dllexport)
#else
#define DECLDIR __declspec(dllimport)
#endif

This macro would tell whether we're importing or exporting a symbol based on our build commands.

Now in tier1lib.h , mark which symbol that will be visible to other project. In each function, add DECLDIR macro such as

DECLDIR void foo();
// or, if you want to export/import whole class' public symbols
class DECLDIR Foo{};

Build it.

Now in the main project, tell VS about where to find the dynamic library. Add include path (where to find headers), library path (where to find *.lib file) and library filename (eg tier1lib.lib ). Copy the resulting *.dll to the main project's output folder and Tier 1 compilation is now completely separated to the main project.