Convert jsonpull to C++ with shared_ptr and std::vector/std::string

Replace the manual malloc/realloc/free memory management in jsonpull
with std::shared_ptr ownership. Each json_object now owns its children
through std::vector<json_object_ptr>; raw back-pointers to parent and
parser remain valid by structural invariant and are cleared on
json_disconnect so detached subtrees can outlive their parser.
Strings become std::string, child arrays become std::vector, and the
old union becomes a struct so non-trivial members can coexist while
preserving the existing o->value.xxx access paths.

The old jsonpull.c is replaced by jsonpull.cpp, json_stringify now
returns std::string, and all callers across tippecanoe, tile-join,
tippecanoe-decode, tippecanoe-json-tool, tippecanoe-overzoom and the
unit tests are updated to use json_object_ptr / json_pull_ptr.

Co-authored-by: Cursor <cursoragent@cursor.com>

tile.cpp

@@ -941,7 +941,7 @@ struct write_tile_args {
 	bool still_dropping = false;
 	int wrote_zoom = 0;
 	size_t tiling_seg = 0;
-	json_object *filter = NULL;
+	json_object_ptr filter;
 	std::vector<std::string> const *unidecode_data;
 	std::atomic<size_t> *dropped_count = NULL;
 	atomic_strategy *strategy = NULL;
@@ -1102,7 +1102,7 @@ struct next_feature_state {
 // This function is called repeatedly from write_tile() to retrieve the next feature
 // from the input stream. If the stream is at an end, it returns a feature with the
 // geometry type set to -2.
-static serial_feature next_feature(decompressor *geoms, std::atomic<long long> *geompos_in, int z, unsigned tx, unsigned ty, unsigned *initial_x, unsigned *initial_y, long long *original_features, long long *unclipped_features, int nextzoom, int maxzoom, int minzoom, int max_zoom_increment, size_t pass, std::atomic<long long> *along, long long alongminus, int buffer, std::atomic<bool> *within, compressor **geomfile, std::atomic<long long> *geompos, long long start_geompos[], std::atomic<double> *oprogress, double todo, const char *fname, int child_shards, json_object *filter, const char *global_stringpool, long long *pool_off, std::vector<std::vector<std::string>> *layer_unmaps, bool first_time, bool compressed, multiplier_state *multiplier_state, std::shared_ptr<std::string> &tile_stringpool, std::vector<std::string> const &unidecode_data, next_feature_state &next_feature_state, double droprate) {
+static serial_feature next_feature(decompressor *geoms, std::atomic<long long> *geompos_in, int z, unsigned tx, unsigned ty, unsigned *initial_x, unsigned *initial_y, long long *original_features, long long *unclipped_features, int nextzoom, int maxzoom, int minzoom, int max_zoom_increment, size_t pass, std::atomic<long long> *along, long long alongminus, int buffer, std::atomic<bool> *within, compressor **geomfile, std::atomic<long long> *geompos, long long start_geompos[], std::atomic<double> *oprogress, double todo, const char *fname, int child_shards, json_object_ptr filter, const char *global_stringpool, long long *pool_off, std::vector<std::vector<std::string>> *layer_unmaps, bool first_time, bool compressed, multiplier_state *multiplier_state, std::shared_ptr<std::string> &tile_stringpool, std::vector<std::string> const &unidecode_data, next_feature_state &next_feature_state, double droprate) {
 	double extra_multiplier_zooms = log(retain_points_multiplier) / log(droprate);
 
 	while (1) {
@@ -1350,7 +1350,7 @@ struct run_prefilter_args {
 	char *global_stringpool = NULL;
 	long long *pool_off = NULL;
 	FILE *prefilter_fp = NULL;
-	json_object *filter = NULL;
+	json_object_ptr filter;
 	std::vector<std::string> const *unidecode_data;
 	bool first_time = false;
 	bool compressed = false;
@@ -1641,7 +1641,7 @@ void skip_tile(decompressor *geoms, std::atomic<long long> *geompos_in, bool com
 	}
 }
 
-long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, char *global_stringpool, int z, const unsigned tx, const unsigned ty, const int detail, int min_detail, sqlite3 *outdb, const char *outdir, int buffer, const char *fname, compressor **geomfile, std::atomic<long long> *geompos, int minzoom, int maxzoom, double todo, std::atomic<long long> *along, long long alongminus, double gamma, int child_shards, long long *pool_off, unsigned *initial_x, unsigned *initial_y, std::atomic<int> *running, double simplification, std::vector<std::map<std::string, layermap_entry>> *layermaps, std::vector<std::vector<std::string>> *layer_unmaps, size_t tiling_seg, size_t pass, unsigned long long mingap, long long minextent, unsigned long long mindrop_sequence, double minattribute, const char *prefilter, const char *postfilter, json_object *filter, write_tile_args *arg, atomic_strategy *strategy_out, bool compressed_input, node *shared_nodes_map, size_t nodepos, std::string const &shared_nodes_bloom, std::vector<std::string> const &unidecode_data, long long estimated_complexity, std::set<zxy> &skip_children_out) {
+long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, char *global_stringpool, int z, const unsigned tx, const unsigned ty, const int detail, int min_detail, sqlite3 *outdb, const char *outdir, int buffer, const char *fname, compressor **geomfile, std::atomic<long long> *geompos, int minzoom, int maxzoom, double todo, std::atomic<long long> *along, long long alongminus, double gamma, int child_shards, long long *pool_off, unsigned *initial_x, unsigned *initial_y, std::atomic<int> *running, double simplification, std::vector<std::map<std::string, layermap_entry>> *layermaps, std::vector<std::vector<std::string>> *layer_unmaps, size_t tiling_seg, size_t pass, unsigned long long mingap, long long minextent, unsigned long long mindrop_sequence, double minattribute, const char *prefilter, const char *postfilter, json_object_ptr filter, write_tile_args *arg, atomic_strategy *strategy_out, bool compressed_input, node *shared_nodes_map, size_t nodepos, std::string const &shared_nodes_bloom, std::vector<std::string> const &unidecode_data, long long estimated_complexity, std::set<zxy> &skip_children_out) {
 	double merge_fraction = 1;
 	double mingap_fraction = 1;
 	double minextent_fraction = 1;
@@ -1775,7 +1775,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 		pthread_t prefilter_writer;
 		run_prefilter_args rpa;	 // here so it stays in scope until joined
 		FILE *prefilter_read_fp = NULL;
-		json_pull *prefilter_jp = NULL;
+		json_pull_ptr prefilter_jp;
 
 		if (z < minzoom) {
 			prefilter = NULL;
@@ -3213,7 +3213,7 @@ exit(EXIT_IMPOSSIBLE);
 	return err_or_null;
 }
 
-int traverse_zooms(int *geomfd, off_t *geom_size, char *global_stringpool, std::atomic<unsigned> *midx, std::atomic<unsigned> *midy, int &maxzoom, int minzoom, sqlite3 *outdb, const char *outdir, int buffer, const char *fname, const char *tmpdir, double gamma, int full_detail, int low_detail, int min_detail, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification, double maxzoom_simplification, std::vector<std::map<std::string, layermap_entry>> &layermaps, const char *prefilter, const char *postfilter, std::unordered_map<std::string, attribute_op> const *attribute_accum, json_object *filter, std::vector<strategy> &strategies, int iz, node *shared_nodes_map, size_t nodepos, std::string const &shared_nodes_bloom, int basezoom, double droprate, std::vector<std::string> const &unidecode_data, std::string const *drop_by_attribute_as_needed_attribute, bool drop_by_attribute_descending) {
+int traverse_zooms(int *geomfd, off_t *geom_size, char *global_stringpool, std::atomic<unsigned> *midx, std::atomic<unsigned> *midy, int &maxzoom, int minzoom, sqlite3 *outdb, const char *outdir, int buffer, const char *fname, const char *tmpdir, double gamma, int full_detail, int low_detail, int min_detail, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification, double maxzoom_simplification, std::vector<std::map<std::string, layermap_entry>> &layermaps, const char *prefilter, const char *postfilter, std::unordered_map<std::string, attribute_op> const *attribute_accum, json_object_ptr filter, std::vector<strategy> &strategies, int iz, node *shared_nodes_map, size_t nodepos, std::string const &shared_nodes_bloom, int basezoom, double droprate, std::vector<std::string> const &unidecode_data, std::string const *drop_by_attribute_as_needed_attribute, bool drop_by_attribute_descending) {
 	last_progress = 0;
 
 	// The existing layermaps are one table per input thread.