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Niels Lohmann
c84e22cc62
A failed allocation while the new elements were copied left the value changed, and with JSON_DIAGNOSTICS stale parent pointers behind. The extra work now happens almost only on the failure path: - Array insert(pos, cnt, val) and insert(pos, first, last) append the copies at the end and rotate them into place. If a copy throws, the appended elements are erased again (noexcept) and the parents are set. Moving a basic_json cannot throw, so reallocation is safe. This is no slower than vector::insert (faster for numbers), needs no temporary array, and keeps the elements that libstdc++ lost on reallocation. - Array insert(pos, val) copies a non-scalar value first and inserts it by move, except at the end, where vector::insert is strong. Scalars keep the direct path. - The object range insert(first, last) into an empty object uses the container's own range insertion and clears the object on an exception. Into a non-empty object it inserts member by member and logs one bit per source member (a new member is detected by the size change; no allocation for the first 256 members); on an exception the members added are erased by walking the source range. No assumption that key_type is string_t. - The parents are set when a failed insertion is undone. The regression test fails every allocation of every insert() overload in turn, for json and ordered_json, and checks the value and its parents. Signed-off-by: Niels Lohmann <mail@nlohmann.me>