On 11/18/25 7:17 PM, Dylan Hatch wrote:
For sframe v3, I believe Indu is planning to add support for marking the
outermost frame. That would be one definitive way to know that the
stack trace made it to the end.
How would this work? Is there a way of determining at compile time
which functions would end up being the outermost frame?
No, the compiler does not emit such a marker.
SFrame information is generated by assembler using the .cfi_*
directives. For the outermost functions, they need to be marked with a:
.cfi_undefined RA
where RA is the default return address register for the ABI.
This mechanism is formalised in the DWARF standard:
"If a Return Address register is defined in the virtual unwind table,
and its rule is undefined (for example, by DW_CFA_undefined), then there
is no return address and no call address, and the virtual unwind of
stack activations is complete."
SFrame relies on this to emit a marker for identifying outermost frame.
