sbf

A Brainfuck interpreter that lets programs perform OS syscalls via a custom instruction, hopefully portable across architectures

Syscall Instruction

When syscall instruction (!) occurs with the cell pointer at cell n:

Cell [n, n+3]	Cell n+4	Cell n+5	Cell [n+6, n+14]	...
syscall number	argc	arg1 type	arg1	...

• Syscall number takes 4 cells (32-bit integer)
• Each argument takes 8 cells (64-bit), the size of a register on 64-bit architecture
• Arg types:
  • 0 (integer)
  • 1 (pointer)
• Pointers should be given as an offset relative to the beginning of the tape. The interpreter will translate the relative address to a real pointer
• All arguments are little-endian

Example

The test program prints "hello\n" twice: first via normal Brainfuck instructions, then via a write syscall. Then, it exits via an exit syscall with exit code 67.

Replace test_prog with the file name corresponding to your platform (e.g. test_prog_macos-arm64).

$ cargo run test_prog
hello
hello
$ echo $?
67

To-Do

• Create a compiler for a higher-level language that compiles into this Brainfuck dialect (thus creating the Brainfuck Virtual Machine?)