Don't use void * arithmetic

src/dump.c

@@ -48,7 +48,7 @@
 void *dump_get(struct dump *d, size_t count, size_t *offset) {
   size_t local_offset = atomic_add(&d->count, count);
   *offset = local_offset + d->file_offset;
-  return d->data + local_offset;
+  return (char *)d->data + local_offset;
 }
 
 /**