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