Add an fn_ptr field to MiriFrame
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The `backtrace-rs` crate can use this to implement `Frame::symbol_address`, which is used to skip frames above the call to `Backtrace::capture` on the stack. The function pointer will not be useable for comparison purposes if the function is generic, as CTFE creates a new function pointer for each cast of a (monomorphized) generic function. However, this already affects code running under Miri, and isn't a problem for `backtrace-rs` (which only casts a non-generic function). I've added logic to allow `MiriFrame` to have either 4 or 5 fields - if a 5th field is present, we write the function pointer to it.
RalfJung
reviewed
Oct 11, 2020
RalfJung
reviewed
Oct 11, 2020
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@RalfJung: Would you like me to add any kind of deprecation warning for the 4-field case, or should we just remove it later without a warning? |
Co-authored-by: Ralf Jung <[email protected]>
Aaron1011
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It's probably not worth it given the low usage. But please add a comment in the code saying that this is deprecated and slated for removal. You say it is for "backwards compatibility", but that might well mean "we will support this forever due to backwards compatibility". |
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Thanks for the PR! |
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📌 Commit c889eba has been approved by |
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☀️ Test successful - checks-actions, checks-travis, status-appveyor |
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The
backtrace-rscrate can use this to implementFrame::symbol_address, which is used to skip framesabove the call to
Backtrace::captureon the stack.The function pointer will not be useable for comparison purposes if the
function is generic, as CTFE creates a new function pointer for each
cast of a (monomorphized) generic function. However, this already
affects code running under Miri, and isn't a problem for
backtrace-rs(which only casts a non-generic function).
I've added logic to allow
MiriFrameto have either 4 or 5 fields - ifa 5th field is present, we write the function pointer to it.