Doesn't even have to be very early... There's lots of 'assume char is signed bugs' in even modern code. So many that ARM gave up on the idea that unsigned char was good (since the underlying ARM architecture supported it better) and their modern ABIs are all signed char. The other thing that EABI fixes is the crazy alignment rules that were out-of-step with the rest of the computer industry that broke a lot of networking and storage code on ARM because its rules caused structs that would otherwise describe the binary layout to be suddenly wrong. Yes, that is an implementation choice, just a poor one that was eventually corrected.

When I was working on FreeBSD/arm only a decade ago, I'd routinely hit both of these issues...

Warner