typedef struct labyrinth void *entrance; // base address of first page block struct labyrinth_room **rooms; // indirect index of free pages atomic_uint_least64_t version; // for atomic exclusivity labyrinth_t; In C, void as a return type means the function returns nothing. But void in parentheses ( allocpagegfpatomic(void) ) would mean no parameters.
void *alloc_page_gfp_atomic_exclusive(labyrinth *ctx); Or as a macro: #define labyrinth_void_alloc(...) define labyrinth void allocpagegfpatomic exclusive
Instead, this keyword string appears to be a — likely a search query from a developer trying to troubleshoot or design a fragment of a custom memory allocator, a lock-free data structure inside a kernel module, or a page allocator for a custom OS. typedef struct labyrinth void *entrance; // base address
Let us break it down piece by piece, then rebuild it into a usable definition. In C/C++, #define is a preprocessor macro. This suggests the author intends to create a macro or a symbolic constant rather than a runtime function. However, a macro for a complex allocator would be unusual; more likely, define is part of a function definition ( #define LABYRINTH_ALLOC_PAGE(...) ) or a configuration header. Let us break it down piece by piece,
No locks, no sleeping, and each page is exclusively owned until freed. struct labyrinth_room atomic void *free_pages; // stack of free pages as a singly-linked list uint32_t hint; ; void *alloc_labyrinth_page_atomic_exclusive(labyrinth_t *lab, unsigned int gfp_flags) // Room selection based on CPU index or hash of PC struct labyrinth_room *room = &lab->rooms[smp_processor_id() % lab->num_rooms];