[brandmeyer]

The jargon for this practice is multiversion programming. Its based on the idea that different people will make different errors when implementing a design. However, in practice we find that errors are actually moderately or even strongly correlated between different programmers. So this practice is rather uncommon.

[nickpsecurity]

It's one of techniques I used to recommend although for anti-subversion instead of safety. I was worried whst you said might turn out true. My solution and hypothesis is that using three, very-different languages should counter that effect. Hard to imagine the same error happening in PreScheme, SPARK, and C.