There's an argument to be made that C++ functional casts are just as dangerous as old style C casts. They have the ability to perform reinterpret casts, causing potentially dangerous bugs in software. On top of this, C++ functional style casts have the same syntactic 'look' as a constructor call. This has the potential, especially when dealing with template code, for a hidden reinterpret cast to be embedded in code without an author realising.
This patch adds a new diagnostic and warning flag (-Whidden-reinterpret-cast) that will fire whenever a C++ functional style cast fails a static cast check but succeeds a reinterpret cast check. This should help identify unintentional reinterpret casts in a codebase.
This work was partly inspired by the following blog post:
The template test in this change takes inspiration from the first example in said blogpost.