How do YOU reduce compile time, and linking time for Visual C++ projects (native C++)?

Question

How do YOU reduce compile time, and linking time for VC++ projects (native C++)?

Please specify if each suggestion applies to debug, release, or both.

Answer 1

We use Xoreax's Incredibuild to run compilation in parallel across multiple machines.

Answer 2

Compile Time:
If you have IncrediBuild, compile time won't be a problem. If you don't have a IncrediBuild, try the "unity build" method. It combine multiple cpp files to a single cpp file so the whole compile time is reduced.
Link Time:
The "unity build" method also contribute to reduce the link time but not much. How ever, you can check if the "Whole global optimization" and "LTCG" are enabled, while these flags make the program fast, they DO make the link SLOW.
Try turning off the "Whole Global Optimization" and set LTCG to "Default" the link time might be reduced by 5/6.
(LTCG stands for Link Time Code Generation)

Answer 3

It may sound obvious to you, but we try to use forward declarations as much as possible, even if it requires to write out long namespace names the type(s) is/are in:

// Forward declaration stuff
namespace plotter { namespace logic { class Plotter; } }

// Real stuff
namespace plotter {
    namespace samples {
        class Window {
            logic::Plotter * mPlotter;
            // ...
        };
    }
}

It greatly reduces the time for compiling also on others compilers. Indeed it applies to all configurations :)

Answer 4

Another useful technique is blobbing. I think it is something similar to what was described by Matt Shaw.

Simply put, you just create one cpp file in which you include other cpp files. You may have two different project configurations, one ordinary and one blob. Of course, blobbing puts some constrains on your code, e.g. class names in unnamed namespaces may clash.

One technique to avoid recompiling the whole code in a blob (as David Rodríguez mentioned) when you change one cpp file - is to have your "working" blob which is created from files modified recently and other ordinary blobs.

We use blobbing at work most of the time, and it reduces project build time, especially link time.

Answer 5

If you have large complex headers that must be included by most of the .cpp files in your build process, and which are not changed very often, you can precompile them. In a Visual C++ project with a typical configuration, this is simply a matter of including them in stdafx.h. This feature has its detractors, but libraries that make full use of templates tend to have a lot of stuff in headers, and precompiled headers are the simplest way to speed up builds in that case.

Answer 6

Also an interesting article from Ned Batchelder: http://nedbatchelder.com/blog/200401/speeding_c_links.html (about C++ on Windows).