Fix swap(array_t&)/swap(object_t&) to update parent pointers under JSON_DIAGNOSTICS - #5464
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…ON_DIAGNOSTICS Both overloads swapped the underlying container storage but never called set_parents(), leaving elements moved into *this with stale m_parent pointers (typically nullptr from the free-standing array_t/object_t). This produced wrong JSON Pointer paths in diagnostic messages and could trip assert_invariant() on subsequent copies. Mirrors the fix already applied in swap(reference other). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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Summary
basic_json::swap(array_t& other)andbasic_json::swap(object_t& other)swap the underlying container storage but never callset_parents(), unlike the genericswap(reference other)overload which does. This leavesm_parentpointers on the moved-in elements stale (pointing into the free-standingarray_t/object_t, typicallynullptr), which:JSON_DIAGNOSTICSis enabled, andassert_invariant()on a subsequent copy in debug/assert-enabled builds.swap(string_t&)andswap(binary_t&)are unaffected since those value types have no children.Fix
Add a
set_parents();call after the existing swap in each overload, mirroring whatswap(reference other)already does.Test plan
tests/src/unit-diagnostics.cppcovering both overloads (checks the diagnostic path string and a subsequent copy-construction).single_include/nlohmann/json.hppviamake amalgamate.Breaking change?
No breaking changes. This only affects the diagnostic path string produced when
JSON_DIAGNOSTICS=1and one of these twoswap()overloads was previously used on a structured value with children — the path becomes correct instead of truncated. No public API signatures change.🤖 Generated with Claude Code