Turning Off Safety Checks
Checked Arithmetic
Scripts under normal builds of Rhai never crash the host system – any panic is a bug.
By default, all arithmetic calculations in Rhai are checked, meaning that the script terminates with a runtime error whenever it detects a numeric over-flow/under-flow condition or an invalid floating-point operation.
This checking can be turned off via the unchecked
feature for higher performance
(but higher risks as well).
let x = 1_000_000_000_000;
x * x; // Normal build - runtime error: multiplication overflow
x * x; // 'unchecked' debug build - panic!
// 'unchecked' release build - overflow with no error
x / 0; // Normal build - runtime error: division by zero
x / 0; // 'unchecked' build - panic!
Other Safety Checks
In addition to overflows, there are many other safety checks performed by Rhai at runtime.
unchecked
turns them all off as well, such as…
Infinite loops
// Normal build - runtime error: exceeds maximum number of operations
loop {
foo();
}
// 'unchecked' build - never terminates!
loop {
foo();
}
Infinite recursion
fn foo() {
foo();
}
foo(); // Normal build - runtime error: exceeds maximum stack depth
foo(); // 'unchecked' build - panic due to stack overflow!
Gigantic data structures
let x = [];
// Normal build - runtime error: array exceeds maximum size
loop {
x += 42;
}
// 'unchecked' build - panic due to out-of-memory!
loop {
x += 42;
}
Improper range iteration
// Normal build - runtime error: zero step
for x in range(0, 10, 0) { ... }
// 'unchecked' build - never terminates!
for x in range(0, 10, 0) { ... }
// Normal build - empty range
for x in range(0, 10, -1) { ... }
// 'unchecked' build - panic due to numeric underflow!
for x in range(0, 10, -1) { ... }