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