Meeting 2026-09-08

[jonathanpallant]

This is the agenda for the next meeting. Please add anything you'd like to discuss below!

• Meetings: Tuesday 8pm Europe/Berlin time
• Join the Matrix chat
• IRC/Matrix logs

The REWG Code of Conduct applies.

[jonathanpallant]

How exactly should an xxxx-rt crate handle user supplied exception handlers?

See rust-embedded/aarch32#223

The specific issue here is that the handler function may or may not want to receive the addr: usize value from the underlying assembly routine, and may return a usize or may return !. We also need to give the function (or create a trampoline with) a magic name so the linker connects it to the assembly routine (c.f. on Cortex-M where the linker puts it in an array of function pointers).

• Should we place the user's function as an 'inner' function, put the specially named trampoline around it? If so, what about any attributes that are applied?
• Should we leave the user's function as-is, and put the specially named trampoline next to it? If so, how can the user apply attributes to the trampoline?
• Should we rename the user's function to have the special name? Is it weird if the function the user wrote isn't in the symbol table?

[diondokter]

Note that on the cortex-m-rt hardfault, you can use the attribute to turn off the trampoline. When you do that, the user function becomes the hardfault handler function and the required signature changes.

[BartMassey]

"Is it weird if the function the user wrote isn't in the symbol table?" I don't think so, as long as its documented. The kind of user doing this deep wizardry presumably will have no trouble with a clear explanation.

[jonathanpallant]

Should turning off the trampoline be unsafe? Can you cause UB by providing a bad handler function? Or should/does the macro do enough checks on the signature (extern "C", correct kinds of argument, correct return type, etc).

[thejpster]

We discussed this - notes in the PR