correct error handling of ftruncate

Makefile

@@ -3,7 +3,7 @@
 
 PROJECT=cow
 AUTHOR=Avril (Flanchan) <flanchan@cumallover.me>
-VERSION=0.1.1
+VERSION=0.1.2
 
 ifeq ($(PREFIX),)
 	PREFIX := /usr/local

src/cow.c

@@ -67,7 +67,7 @@ static inline int shm_fd(size_t size)
 	int fd = memfd_create("cow_create:shm_fd", 0);
 #endif
 	if(fd<=0) die("cow_create:shm_fd:memfd_create");
-	ftruncate(fd, size);
+	if(ftruncate(fd, size) != 0) die("cow_create:shm_fd:ftruncate");
 	return fd;
 }