What is the Unix ABI?

Answer 1

First of all ABI stands for Application Binary Interface this describes:

* data type size and alignment; * how parameters to function should be passed; * how return value should be set; * how application should talk (make syscalls) to operating system; As you can see it describes very low level and how everything interacts. Each operating system does have it's own ABI, even virtual machines or programming languages run-time could have their own ABI. Sometimes it is referred as Function Calling Conventions.

For example all parameters in UNIX (assembly language) are passed by pushing them into stack in specific order. If we would talk about Linux and Windows parameters are put into CPU registers.

There is very little detailed information in one place that describes those conventions.