Return const references from member accessors#46
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Detector::panels() returned std::vector<Panel> by value. Binding a reference to panels()[0] bound to a subobject of that temporary, which is destroyed at the end of the statement, leaving the panel dangling for its whole lifetime. It compiled without warnings and failed only non-deterministically at runtime (observed downstream as corrupt Panel::get_origin() values). It also deep-copied the whole panel vector on every call. Change Detector::panels() to return const std::vector<Panel> &, and audit the remaining DX2 accessors for the same pattern. Crystal:: get_unit_cell(), Crystal::get_space_group() and ImageSequence:: filename() returned heap-owning members by value and are now const references too. Computed accessors and small trivially-copyable value types are intentionally left returning by value.
jbeilstenedmands
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This PR fixes
Detector::panels()returningstd::vector<Panel>byvalue, which created dangling references for callers binding to
panels()[0]and deep-copied the heavy panel vector on every call. Italso audits the remaining DX2 accessors so we don't hit the same silent,
non-error-throwing issue elsewhere.
Changes:
Detector::panels()(include/dx2/detector.hpp,dx2/detector.cxx) fromstd::vector<Panel>toconst std::vector<Panel> &, the idiomatic accessor form. This removes boththe dangling-reference issue and the per-call deep copy of every heavy
Panel.beam,crystal,goniometer,scan,experiment,imagesequenceandreflectionfor the same pattern.Three further member-backed accessors returned heap-owning types by
value and are now const references:
Crystal::get_unit_cell()now returnsconst gemmi::UnitCell &Crystal::get_space_group()now returnsconst gemmi::SpaceGroup &ImageSequence::filename()now returnsconst std::string &rationale:
Beam::get_s0(),Scan::get_oscillation(),etc.) construct a new value and must return by value.
fixed-size
Matrix3d/Vector3d,std::array<…,2>,double) arestack-only, cheap to copy, and carry no dangling-subobject risk in
practice.
ReflectionTablevector accessors andExperiment::identifier()/goniometer()already use theconst-reference form.
return of the changed accessors, so there were no call-site changes.
Existing
gemmi::UnitCell cell = crystal.get_unit_cell();copiesremain valid.
This removes a runtime-only, non-deterministic memory-corruption class
from the detector model and brings the rest of the DX2 accessors into a
consistent, audited state.
Closes #45.