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* Fix stack overflow converting deep values between specializations Constructing a basic_json from another specialization (json to ordered_json or back, also via get<ordered_json>()) converted every container with its range constructor, which calls the converting constructor for each element. The call stack therefore grew with every nesting level, and a value nested some 30,000 levels deep overflowed it. The conversion now bounds its descent the way the copy constructor does since #5387: the first 128 levels are converted exactly as before, and below that convert_iteratively() finishes the value with an explicit stack. It builds each container bottom-up from its converted elements with the container's range constructor, so member order and keys that become equal are handled as before, and it gives a value its type only once its container exists, so an exception leaves nothing behind that cannot be destroyed. Parents (JSON_DIAGNOSTICS) and positions (JSON_DIAGNOSTIC_POSITIONS) are set for every value. Converting a null value no longer resets its positions: the constructor assigned null to a value that already was null, which swapped in the positions of the temporary. Fixes #5650. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Explain why converting null keeps positions and why next is a reference Review feedback on #5723 (gregmarr): clarify in comments that the converting constructor has already copied the positions of val, which the null case keeps like every other case, and that next must be a reference into pending so that ++next advances the stored iterator. Comments only; no code change. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Refer to recursion_depth_limit() in the convert_structured() docs The comment still named nesting_depth_limit, which #5637 removed on develop in favor of detail::recursion_depth_limit(). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Advance the pending iterator through pending.back() and shorten the null comment Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>