main and failsafe — Mandatory Functions

Every Nitpick program must define both main and failsafe.

main

Program entry point. Must call exit() (not pass/fail):

func:main = int32() {
    println("Hello, world!");
    exit 0;
};

• Signature: func:main = int32() — takes no arguments (argc/argv via sys)
• Must call exit(code) where code is an int32
• exit 0 = success, nonzero = error
• pass/fail are not valid in main

failsafe

Mandatory unrecoverable error handler for explicit unrecoverable paths:

func:failsafe = int32(tbb32:err) {
    println("Fatal error occurred");
    exit 1;
};

• Signature: func:failsafe = int32(tbb32:err) — receives error code
• Must call exit(code) where code > 0
• pass/fail are not valid in failsafe
• Called by !!! err; shorthand
• This is Nitpick's last line of defense — it must always exit

Source-level expr ?! fallback is not a failsafe-dispatch operator as of v0.33.6; it is emphatic Result fallback unwrap. See guide/result/06-question-bang.md.

Required in Every Program

Both functions must be present. A program without either will not compile.

Paren Syntax

exit supports both keyword and paren syntax:

exit 0;      // keyword form
exit(0);     // paren form

Note: OS-level exit-code truncation

Nitpick passes the full int32 you give to exit straight to the operating system, but on Unix-like systems the parent process (your shell, a test runner, wait()/waitpid(), etc.) only observes the low 8 bits of the exit status. This is the POSIX WEXITSTATUS contract — it is the same in C, C++, Rust, Go, Python, Java, and every other language that exits via libc.

Concretely, exit 1234 will be reported as 1234 & 0xff == 210 by the shell. This is not a Nitpick bug; it is a property of the Unix process API.

If you need to communicate a value larger than 255 from a program, write it to stdout and have the consumer parse it; reserve the exit code for a small, well-known status (0 = success, nonzero = error class).