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34 lines
1.1 KiB
Markdown
34 lines
1.1 KiB
Markdown
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# 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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ERROR:panic_log -- panicked at 'index out of bounds: the len is 3 but the index is 3', src/bin/panic.rs:29:13
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stack backtrace:
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0: 0x000022f0 - __bkpt
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1: 0x00002010 - rust_begin_unwind
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2: 0x00000338 - core::panicking::panic_fmt
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3: 0x00000216 - core::panicking::panic_bounds_check
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4: 0x0000016a - panic::bar
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5: 0x00000158 - panic::foo
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6: 0x00000192 - panic::__cortex_m_rt_main
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7: 0x00000178 - main
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8: 0x0000199e - Reset
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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: comment out the `panic_log` 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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log::error!("{}", info);
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loop {
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asm::bkpt()
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}
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}
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```
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Now run the program again. Try changing the format string of the `error!` macro.
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