rust-embedded / rust-embedded/cortex-m
Check that `SYST.set_reload`'s argument is valid
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Description
The SYST.set_reload takes a number of cycles as an argument. Even though the type of this argument is an u32, only values that fit on 24 bits are valid. The code does document this caveat, however in practice there is no check being enforced.
As a result, it's very easy to pass a value that's too large and that will silently overflow, leading to a hard-to-diagnose incorrect behavior.
Would it make sense to add an assertion about the argument there?
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Research direction
Start in cortex-m/src/peripheral/syst.rs around the documented SYST.set_reload caveat at line 178, then inspect the set_reload entry point and its argument handling. Done means values exceeding the valid 24-bit range are rejected instead of silently overflowing, with behavior consistent with the existing documentation.
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Assessment
- Tech stack
- rust
- Domain
- embedded-iot
- Issue type
- Bug
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Quiet
- Clarity
- Clearly specified
- Newbie friendliness
- 76/100