AOS - Applied Operating System
To be written in ATS (http://www.ats-lang.org/), which is a programming language that has a very flexible type system, supporting dependent and linear types. The language compiles straightforwardly to C, with no garbage collection (by default), making it very useful for low-level programming. ATS's type system can be used to prove at compile-time, among many other properties, the absence of memory leaks, double frees, dangling pointers, uninitialised value or pointer use and integer overflow.
AOS defines operators on integers such that they cannot be called if the operation would overflow. This requires ATS's constraint solver to handle large integers. The current release of ATS, "Anairiats", is unable to handle such large numbers in the constraint solver (ironically, integers in the constraint solver overflow), so included with AOS is a patch to use bignums in the constraint solver.
The ATS compiler is written in ATS, but because it translates to C, the compiler can be boot-strapped by compiling intermediate C sources. AOS's makefile contains a rule to check out (from subversion) and build a copy of the ATS compiler automatically. Run:
in the AOS directory. Then you can compile AOS with:
make depend make
make V=1 to echo commands.
- 486SX-compatible. There's no reason it shouldn't run on i386 too, but it's not tested.
- It prints greetings to the serial port!
AOS compiles to a
ELF file called, believe it or not,
kernel, linked at
0x00100000. A small
amount of code in
start.S identity-maps the first four megabytes of physical
memory, turns on paging and jumps to ATS code, which can be linked at virtual
addresses different to the physical addresses (but isn't now).
Use a multiboot-compliant boot-loader such as [GNU GRUB] (http://www.gnu.org/software/grub/) to boot AOS, or run it in QEMU with
qemu -kernel kernel