Add a hack to keep FFI symbols in optimized binary

src/CMakeLists.txt

@@ -74,6 +74,7 @@ set (common_sources
      opts.c
      cpu_feature.c
      fiob.c
+     ffisyms.cc
      lua/fiber.cc
      lua/trigger.cc
      lua/admin.cc

src/ffisyms.cc

+#include <bit/bit.h>
+#include <lib/msgpuck/msgpuck.h>
+
+/*
+ * A special hack to cc/ld to keep symbols in an optimized binary.
+ * Please add your symbols to this array if you plan to use it from LuaJIT FFI.
+ */
+void *ffi_symbols[] = {
+	(void *) bswap_u32,
+	(void *) bswap_u64,
+	(void *) mp_bswap_float,
+	(void *) mp_bswap_double
+};

src/tarantool.cc

@@ -571,6 +571,13 @@ tarantool_free(void)
 		fclose(cfg_out);
 		free(cfg_log);
 	}
+
+	/* A hack for cc/ld, see ffisyms.c */
+	if (time(NULL) == 0) {
+		/* never executed */
+		extern void *ffi_symbols[];
+		write(0, ffi_symbols, 0);
+	}
 }
 
 int