This was highly informative, but the overall tone comes across as (to me) overly condescending, with lots of complaints about having to download "random" software. It's not made clear what the OP's author would expect, where the software can come from in order not to be random.
Also, as has been pointed out in comments on the OP site too, the programming language on the Arduino is not C but Wiring/C++. I see people have pointed that out here, too already.
I'm also curious how large the OP's software was, since it was never considered to manually inspect it for overflow once it was deemed impossible to get the proper warnings exposed. Evidently rewriting it in Rust and getting it to compile was enough to fix the overflow problems since the Rust software ran correctly. Sounds like the code was not too massive (it's an 8-bit chip after all so it is probably not doing something super-complicated) and it should have been possible to review it and figure out the problem.
These are boards with 8K memory total, meaning the program in question would very likely fit on a single monitor screen. Dodging the debugging step and reaching for your one true hammer (Rust in this case) speaks more to me about the author's "pricipaled" engineering anything else in this post.
Also, as has been pointed out in comments on the OP site too, the programming language on the Arduino is not C but Wiring/C++. I see people have pointed that out here, too already.
I'm also curious how large the OP's software was, since it was never considered to manually inspect it for overflow once it was deemed impossible to get the proper warnings exposed. Evidently rewriting it in Rust and getting it to compile was enough to fix the overflow problems since the Rust software ran correctly. Sounds like the code was not too massive (it's an 8-bit chip after all so it is probably not doing something super-complicated) and it should have been possible to review it and figure out the problem.