Add a way to run tippecanoe single-threaded for profiling

Makefile

@@ -58,7 +58,7 @@ C = $(wildcard *.c) $(wildcard *.cpp)
 INCLUDES = -I/usr/local/include -I.
 LIBS = -L/usr/local/lib
 
-tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o sort.o attribute.o
+tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o projection.o memfile.o mvt.o serial.o main.o text.o dirtiles.o pmtiles_file.o plugin.o read_json.o write_json.o geobuf.o flatgeobuf.o evaluator.o geocsv.o csv.o geojson-loop.o json_logger.o visvalingam.o compression.o clip.o sort.o attribute.o thread.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-enumerate: enumerate.o
@@ -67,7 +67,7 @@ tippecanoe-enumerate: enumerate.o
 tippecanoe-decode: decode.o projection.o mvt.o write_json.o text.o jsonpull/jsonpull.o dirtiles.o pmtiles_file.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3
 
-tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o evaluator.o csv.o write_json.o pmtiles_file.o clip.o attribute.o
+tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o evaluator.o csv.o write_json.o pmtiles_file.o clip.o attribute.o thread.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o

flatgeobuf.cpp

@@ -7,6 +7,7 @@
 #include "milo/dtoa_milo.h"
 #include "main.hpp"
 #include "errors.hpp"
+#include "thread.hpp"
 
 static constexpr uint8_t magicbytes[8] = { 0x66, 0x67, 0x62, 0x03, 0x66, 0x67, 0x62, 0x01 };
 
@@ -303,7 +304,7 @@ void fgbRunQueue() {
 	}
 
 	for (size_t i = 0; i < CPUS; i++) {
-		if (pthread_create(&pthreads[i], NULL, fgb_run_parse_feature, &qra[i]) != 0) {
+		if (thread_create(&pthreads[i], NULL, fgb_run_parse_feature, &qra[i]) != 0) {
 			perror("pthread_create");
 			exit(EXIT_PTHREAD);
 		}

geobuf.cpp

@@ -15,6 +15,7 @@
 #include "jsonpull/jsonpull.h"
 #include "text.hpp"
 #include "errors.hpp"
+#include "thread.hpp"
 
 #define POINT 0
 #define MULTIPOINT 1
@@ -465,7 +466,7 @@ void runQueue() {
 	}
 
 	for (size_t i = 0; i < CPUS; i++) {
-		if (pthread_create(&pthreads[i], NULL, run_parse_feature, &qra[i]) != 0) {
+		if (thread_create(&pthreads[i], NULL, run_parse_feature, &qra[i]) != 0) {
 			perror("pthread_create");
 			exit(EXIT_PTHREAD);
 		}

main.cpp

@@ -67,6 +67,7 @@
 #include "read_json.hpp"
 #include "sort.hpp"
 #include "attribute.hpp"
+#include "thread.hpp"
 
 static int low_detail = 12;
 static int full_detail = -1;
@@ -518,7 +519,7 @@ void do_read_parallel(char *map, long long len, long long initial_offset, const
 	}
 
 	for (size_t i = 0; i < CPUS; i++) {
-		if (pthread_create(&pthreads[i], NULL, run_parse_json, &pja[i]) != 0) {
+		if (thread_create(&pthreads[i], NULL, run_parse_json, &pja[i]) != 0) {
 			perror("pthread_create");
 			exit(EXIT_PTHREAD);
 		}
@@ -735,7 +736,7 @@ void start_parsing(int fd, STREAM *fp, long long offset, long long len, std::ato
 	rpa->want_dist = want_dist;
 	rpa->filters = filters;
 
-	if (pthread_create(parallel_parser, NULL, run_read_parallel, rpa) != 0) {
+	if (thread_create(parallel_parser, NULL, run_read_parallel, rpa) != 0) {
 		perror("pthread_create");
 		exit(EXIT_PTHREAD);
 	}
@@ -931,7 +932,7 @@ void radix1(int *geomfds_in, int *indexfds_in, int inputs, int prefix, int split
 				}
 
 				for (size_t a = 0; a < CPUS; a++) {
-					if (pthread_create(&pthreads[a], NULL, run_sort, &args[a]) != 0) {
+					if (thread_create(&pthreads[a], NULL, run_sort, &args[a]) != 0) {
 						perror("pthread_create");
 						exit(EXIT_PTHREAD);
 					}

plugin.cpp

@@ -25,6 +25,7 @@
 #include "geometry.hpp"
 #include "serial.hpp"
 #include "errors.hpp"
+#include "thread.hpp"
 
 extern "C" {
 #include "jsonpull/jsonpull.h"
@@ -643,7 +644,7 @@ std::vector<mvt_layer> filter_layers(const char *filter, std::vector<mvt_layer>
 	wa.extent = extent;
 
 	pthread_t writer;
-	if (pthread_create(&writer, NULL, run_writer, &wa) != 0) {
+	if (thread_create(&writer, NULL, run_writer, &wa) != 0) {
 		perror("pthread_create (filter writer)");
 		exit(EXIT_PTHREAD);
 	}

thread.cpp

@@ -0,0 +1,22 @@
+#include <stdlib.h>
+#include "thread.hpp"
+
+// It is harder to profile tippecanoe because of its normal use of multiple threads.
+// If you set TIPPECANOE_NO_THREADS in the environment, it will run everything in
+// the main thread instead for more straightforward profiling. (The threads will
+// then still be created so they will be reaped, but they will immediately return.)
+
+static const char *no_threads = getenv("TIPPECANOE_NO_THREADS");
+
+static void *do_nothing(void *arg) {
+	return arg;
+}
+
+int thread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg) {
+	if (no_threads != NULL) {
+		void *ret = start_routine(arg);
+		return pthread_create(thread, attr, do_nothing, ret);
+	} else {
+		return pthread_create(thread, attr, start_routine, arg);
+	}
+}

thread.hpp

@@ -0,0 +1,3 @@
+#include <pthread.h>
+
+int thread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg);

tile-join.cpp

@@ -42,6 +42,7 @@
 #include "milo/dtoa_milo.h"
 #include "errors.hpp"
 #include "geometry.hpp"
+#include "thread.hpp"
 
 int pk = false;
 int pC = false;
@@ -812,7 +813,7 @@ void dispatch_tasks(std::map<zxy, std::vector<std::string>> &tasks, std::vector<
 	}
 
 	for (size_t i = 0; i < CPUS; i++) {
-		if (pthread_create(&pthreads[i], NULL, join_worker, &args[i]) != 0) {
+		if (thread_create(&pthreads[i], NULL, join_worker, &args[i]) != 0) {
 			perror("pthread_create");
 			exit(EXIT_PTHREAD);
 		}

tile.cpp

@@ -45,6 +45,7 @@
 #include "compression.hpp"
 #include "protozero/varint.hpp"
 #include "attribute.hpp"
+#include "thread.hpp"
 
 extern "C" {
 #include "jsonpull/jsonpull.h"
@@ -2152,7 +2153,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 			rpa.first_time = first_time;
 			rpa.compressed = compressed_input;
 
-			if (pthread_create(&prefilter_writer, NULL, run_prefilter, &rpa) != 0) {
+			if (thread_create(&prefilter_writer, NULL, run_prefilter, &rpa) != 0) {
 				perror("pthread_create (prefilter writer)");
 				exit(EXIT_PTHREAD);
 			}
@@ -2561,7 +2562,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 			args[i].nodepos = nodepos;
 
 			if (tasks > 1) {
-				if (pthread_create(&pthreads[i], NULL, partial_feature_worker, &args[i]) != 0) {
+				if (thread_create(&pthreads[i], NULL, partial_feature_worker, &args[i]) != 0) {
 					perror("pthread_create");
 					exit(EXIT_PTHREAD);
 				}
@@ -3381,7 +3382,7 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *stringpool, std::atomic<
 				args[thread].shared_nodes_map = shared_nodes_map;
 				args[thread].nodepos = nodepos;
 
-				if (pthread_create(&pthreads[thread], NULL, run_thread, &args[thread]) != 0) {
+				if (thread_create(&pthreads[thread], NULL, run_thread, &args[thread]) != 0) {
 					perror("pthread_create");
 					exit(EXIT_PTHREAD);
 				}