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c++visual-c++compiler-warningsenforcement

Good approaches to enforce building with increased warning level for new C++ code

I've inherited a large C++ codebase for several Windows applications that successfully is in use by many customers.

  • The codebase is large, >1mill LOC.
  • The codebase has a history of 15+ years.
  • The codebase is in some areas dominated by C programming style and/or not very modern C++ style, e.g. not using Standard C++ collections and algorithms.
  • The codebase has unfortunately only been compiled with warning level 2 (/W2 in Visual C++). I would like to increase to level 3 (/W3) to increase security and prepare for 64-bit.

The most problematic point in the increase to warning level 3 are the many warnings received involving signed/unsigned mismatches and I recognize that it will be a very large task to resolve all those for the existing codebase.

What would be a good approach to ensure and enforce that new code committed to the codebase are compiled with the increased warning level?

In more general terms the question could be rephrased to how you enforce increased programming quality into new committed code. If you don't do anything, new code has, in my experience, a tendency to be affected and styled similar to existing code, rather than being improved to more modern standards.

Solution

  • I would even go as far as going to warning level 4 (/W4).

    Since you're using Visual Studio, it's quite easy to suppress bothersome warnings like signed vs unsigned comparision:

    #pragma warning(disable:NNNN)

    Where NNNN is the number of your warning. Now put all those disabled warnings in a header file (say, "tedious_warnings.h") and force-include that header file everywhere - Project Properties -> C/C++ -> Advanced -> Forced Include File.
    Later on, or better, ASAP, remove the force include and work your way through the warnings, since most of them are quite easy to fix (size_t instead if int, etc).