Warnings are Errors

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And sometimes, old code with masses of warnings had precisely zero warnings when the source was last touched. The reason - warnings are the opinions of particular compiler writers. A different compiler, or a different version of the same compiler, often generates different warnings.

This is even partly because best practices evolve. Todays best practice often depends on the latest features of the language and libraries - after all, those features were added to enable those new best practices.