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51 lines
2.2 KiB
Markdown
51 lines
2.2 KiB
Markdown
# Panicking
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✅ Open the `src/bin/panic.rs` file and click the "Run" button.
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This program attempts to index an array beyond its length and this results in a panic.
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``` console
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────────────────────────────────────────────────────────────────────────────────
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ERROR panicked at 'index out of bounds: the len is 3 but the index is 3', src/bin/panic.rs:32:13
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────────────────────────────────────────────────────────────────────────────────
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stack backtrace:
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0: HardFaultTrampoline
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<exception entry>
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1: lib::inline::__udf
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at ./asm/inline.rs:172:5
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2: __udf
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at ./asm/lib.rs:49:17
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3: cortex_m::asm::udf
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at /Users/name/.cargo/registry/src/github.com-1ecc6299db9ec823/cortex-m-0.7.3/src/asm.rs:43:5
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4: rust_begin_unwind
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at /Users/name/.cargo/registry/src/github.com-1ecc6299db9ec823/panic-probe-0.3.0/src/lib.rs:72:9
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5: core::panicking::panic_fmt
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at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:100:14
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6: core::panicking::panic_bounds_check
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at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:76:5
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7: panic::bar
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at src/bin/panic.rs:32:13
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8: panic::foo
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at src/bin/panic.rs:25:5
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9: panic::__cortex_m_rt_main
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at src/bin/panic.rs:15:5
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10: main
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at src/bin/panic.rs:11:1
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11: Reset
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(HOST) ERROR the program panicked
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```
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In `no_std` programs the behavior of panic is defined using the `#[panic_handler]` attribute. In the example, the *panic handler* is defined in the `panic_log` crate but we can also implement it manually:
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✅ Comment out the `use apps as _;` import and add the following function to the example:
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``` rust
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#[panic_handler]
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fn panic(info: &core::panic::PanicInfo) -> ! {
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defmt::error!("{}", defmt::Debug2Format(info));
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asm::udf();
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}
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```
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Now run the program again. Try changing the format string of the `panic!` macro.
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