AP_Common: add SITL check for matching alt frame in linearly_interpolate_alt#33079
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I would vote to put the check in the |
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Thanks @IamPete1 , that's the better design. Moved the check into |
rmackay9
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May 17, 2026
…ate_alt linearly_interpolate_alt() interpolates altitude between two Location endpoints and only produces meaningful results when both endpoints share an alt frame; mixing frames produces nonsense altitudes. Add a SITL-only panic at the top of the function so the contract is checked for every caller (BendyRulerHorizontal and Dijkstras path handling in AC_WPNav_OA, plus any future callers), as suggested by IamPete1 in code review. Fixes ArduPilot#32926
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peterbarker
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May 20, 2026
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Incidentally, throwing a "flow_of_control" internal error would have been perfectly valid - if it happens on a real aircraft bad things are going to happen. |
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Summary
Fixes #32926.
update_wpnav()callslinearly_interpolate_alt()againstorigin_locanddestination_locfor both the BendyRulerHorizontal and Dijkstras path-handling branches. That helper's contract is that its two endpoint Locations share an alt frame; mixing frames produces meaningless interpolated altitudes.Today the two locations are always constructed from the same
_is_terrain_alt_oabakconditional so the invariant holds, but there's no runtime check to catch a future change that breaks it. Added a SITL-onlyINTERNAL_ERRORright after the Locations are constructed.Classification & Testing
Built ArduCopter SITL on macOS (arm64). With the current code path the alt frames match by construction, so the new check does not fire (no behavior change). The check is guarded by
#if CONFIG_HAL_BOARD == HAL_BOARD_SITLso production builds are unaffected.