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#![allow(unused_assignments)]
// expect-exit-status-101
fn might_overflow(to_add: u32) -> u32 {
if to_add > 5 {
println!("this will probably overflow");
}
let add_to = u32::MAX - 5;
println!("does {} + {} overflow?", add_to, to_add);
let result = to_add + add_to;
println!("continuing after overflow check");
result
}
fn main() -> Result<(),u8> {
let mut countdown = 10;
while countdown > 0 {
if countdown == 1 {
let result = might_overflow(10);
println!("Result: {}", result);
} else if countdown < 5 {
let result = might_overflow(1);
println!("Result: {}", result);
}
countdown -= 1;
}
Ok(())
}
// Notes:
// 1. Compare this program and its coverage results to those of the very similar test `assert.rs`,
// and similar tests `panic_unwind.rs`, abort.rs` and `try_error_result.rs`.
// 2. This test confirms the coverage generated when a program passes or fails a
// compiler-generated `TerminatorKind::Assert` (based on an overflow check, in this case).
// 3. Similar to how the coverage instrumentation handles `TerminatorKind::Call`,
// compiler-generated assertion failures are assumed to be a symptom of a program bug, not
// expected behavior. To simplify the coverage graphs and keep instrumented programs as
// small and fast as possible, `Assert` terminators are assumed to always succeed, and
// therefore are considered "non-branching" terminators. So, an `Assert` terminator does not
// get its own coverage counter.
// 4. After an unhandled panic or failed Assert, coverage results may not always be intuitive.
// In this test, the final count for the statements after the `if` block in `might_overflow()`
// is 4, even though the lines after `to_add + add_to` were executed only 3 times. Depending
// on the MIR graph and the structure of the code, this count could have been 3 (which might
// have been valid for the overflowed add `+`, but should have been 4 for the lines before
// the overflow. The reason for this potential uncertainty is, a `CounterKind` is incremented
// via StatementKind::Counter at the end of the block, but (as in the case in this test),
// a CounterKind::Expression is always evaluated. In this case, the expression was based on
// a `Counter` incremented as part of the evaluation of the `if` expression, which was
// executed, and counted, 4 times, before reaching the overflow add.
// If the program did not overflow, the coverage for `might_overflow()` would look like this:
//
// 4| |fn might_overflow(to_add: u32) -> u32 {
// 5| 4| if to_add > 5 {
// 6| 0| println!("this will probably overflow");
// 7| 4| }
// 8| 4| let add_to = u32::MAX - 5;
// 9| 4| println!("does {} + {} overflow?", add_to, to_add);
// 10| 4| let result = to_add + add_to;
// 11| 4| println!("continuing after overflow check");
// 12| 4| result
// 13| 4|}
|
