mirror of https://github.com/rust-lang/rust.git
65 lines
3.9 KiB
Plaintext
65 lines
3.9 KiB
Plaintext
1| |#![allow(unused_assignments)]
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2| |// expect-exit-status-101
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3| |
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4| 4|fn might_overflow(to_add: u32) -> u32 {
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5| 4| if to_add > 5 {
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6| 1| println!("this will probably overflow");
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7| 3| }
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8| 4| let add_to = u32::MAX - 5;
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9| 4| println!("does {} + {} overflow?", add_to, to_add);
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10| 4| let result = to_add + add_to;
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11| 4| println!("continuing after overflow check");
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12| 4| result
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13| 4|}
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14| |
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15| 1|fn main() -> Result<(),u8> {
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16| 1| let mut countdown = 10;
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17| 11| while countdown > 0 {
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18| 11| if countdown == 1 {
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19| 1| let result = might_overflow(10);
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20| 1| println!("Result: {}", result);
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21| 10| } else if countdown < 5 {
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22| 3| let result = might_overflow(1);
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23| 3| println!("Result: {}", result);
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24| 6| }
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25| 10| countdown -= 1;
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26| | }
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27| 0| Ok(())
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28| 0|}
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29| |
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30| |// Notes:
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31| |// 1. Compare this program and its coverage results to those of the very similar test `assert.rs`,
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32| |// and similar tests `panic_unwind.rs`, abort.rs` and `try_error_result.rs`.
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33| |// 2. This test confirms the coverage generated when a program passes or fails a
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34| |// compiler-generated `TerminatorKind::Assert` (based on an overflow check, in this case).
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35| |// 3. Similar to how the coverage instrumentation handles `TerminatorKind::Call`,
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36| |// compiler-generated assertion failures are assumed to be a symptom of a program bug, not
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37| |// expected behavior. To simplify the coverage graphs and keep instrumented programs as
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38| |// small and fast as possible, `Assert` terminators are assumed to always succeed, and
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39| |// therefore are considered "non-branching" terminators. So, an `Assert` terminator does not
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40| |// get its own coverage counter.
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41| |// 4. After an unhandled panic or failed Assert, coverage results may not always be intuitive.
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42| |// In this test, the final count for the statements after the `if` block in `might_overflow()`
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43| |// is 4, even though the lines after `to_add + add_to` were executed only 3 times. Depending
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44| |// on the MIR graph and the structure of the code, this count could have been 3 (which might
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45| |// have been valid for the overflowed add `+`, but should have been 4 for the lines before
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46| |// the overflow. The reason for this potential uncertainty is, a `CounterKind` is incremented
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47| |// via StatementKind::Counter at the end of the block, but (as in the case in this test),
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48| |// a CounterKind::Expression is always evaluated. In this case, the expression was based on
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49| |// a `Counter` incremented as part of the evaluation of the `if` expression, which was
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50| |// executed, and counted, 4 times, before reaching the overflow add.
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51| |
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52| |// If the program did not overflow, the coverage for `might_overflow()` would look like this:
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53| |//
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54| |// 4| |fn might_overflow(to_add: u32) -> u32 {
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55| |// 5| 4| if to_add > 5 {
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56| |// 6| 0| println!("this will probably overflow");
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57| |// 7| 4| }
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58| |// 8| 4| let add_to = u32::MAX - 5;
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59| |// 9| 4| println!("does {} + {} overflow?", add_to, to_add);
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60| |// 10| 4| let result = to_add + add_to;
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61| |// 11| 4| println!("continuing after overflow check");
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62| |// 12| 4| result
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63| |// 13| 4|}
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