[bluGill]

It is not uncommon to realize your C program is valid C++ and get a performance improvement just by building with a C++ compiler no other change. The difference is small but C++ has a stronger type system which allows the compiler a few more optimizations. Of course it is possible that resulting program no longer does what you want but actually needing weaker types is rare.

Restrict could make things go different but I've never heard someone say otherwise.

Note that we are talking about differences that are tiny here. They can be measured if you are careful but they are almost guaranteed to not be something anyone would notice if they were not measuring