A common guideline in best coding practices is to never ignore compiler warnings, and always use the highest warning level possible. For Microsoft C/C++ compilers, this mean level 4 (/W4).

But just because your code compiles cleanly under level 4, it doesn’t mean external libraries would too.

Let’s take Boost library as an example. It is arguably the most well written C++ library in the world. Yet it is not cleared of level 4 warning until 1.40.

The truth is that level 4 warning level is harsh (and often silly), and some code are just not fit to make the cut.

Use L3 for the Uglies

For ugly header files that aren’t designed with level 4 warning in mind, just compile them with level 3 with the #pragma warning(push,3) command.

Here’s an example.

#pragma warning( push, 3 ) // boost make_shared has L4 warnings, so use L3.
	#include <boost/make_shared.hpp>
#pragma warning(pop) // resume to original warning level (4)

An often suggested alternative is to use #pragma warning(disable:xyz), where xyz is the warning number.
This solution is clumsy because it requires you to find out every single warning emitted from every external header file, and then disable them one at a time. I am too busy (lazy) for that. 🙂