What is the reason for the weird `{ code };` blocks everywhere and is the below code machine generated?

```c ((PageSize) (chunk->pageSize - ((PageSize) ((PageSize) ((PageSize) (sizeof(Page) + (sizeof(struct _Block))) + (PageSize) ((sizeof(double)) - 1u)) & ((PageSize) (~((PageSize) ((sizeof(double)) - 1u)))))) - ((PageSize) ((PageSize) ((PageSize) ((sizeof(FreeBlock) + sizeof(PageSize))) + (PageSize) (((((sizeof(double)) > (4)) ? (sizeof(double)) : (4))) - ```