Program Execution

A program is a complete, executable Ori application.

Entry Point

Every executable program must have exactly one @main function.

main_function = "@main" "(" [ "args" ":" "[" "str" "]" ] ")" "->" ( "void" | "int" ) "=" expression .

Valid signatures:

@main () -> void = ...
@main () -> int = ...
@main (args: [str]) -> void = ...
@main (args: [str]) -> int = ...

The args parameter, if present, contains command-line arguments passed to the program. It does not include the program name.

// invoked as: ori run program.ori hello world
@main (args: [str]) -> void = run(
    // args = ["hello", "world"]
    print(args[0]),  // prints "hello"
)

Initialization

Program initialization proceeds in the following order:

1. All modules are initialized eagerly
2. Config variables ($name) are evaluated in dependency order
3. @main is invoked

Config Variables

Config variables are compile-time constants evaluated before program execution.

$timeout = 30s
$max_retries = 3
$double_timeout = $timeout * 2  // references other config

Config variables may reference other config variables. The compiler determines evaluation order from dependencies. Circular dependencies are an error.

Module Initialization

All imported modules are initialized before @main runs. Initialization order is determined by the module dependency graph. A module is initialized after all modules it imports.

Termination

Normal Termination

A program terminates normally when @main returns.

@main () -> int = run(
    let success = do_work(),
    if success then 0 else 1,
)

Panic Termination

A program terminates abnormally when an unhandled panic occurs.

On panic:

1. Error message is printed to stderr
2. Stack trace is printed to stderr
3. Program exits with code 1

@main () -> void = run(
    let list = [1, 2, 3],
    list[10],  // panic: index out of bounds
)

See Errors and Panics for panic semantics.