/* * libc/stdlib/malloc/malloc.h -- small malloc implementation * * Copyright (C) 2002 NEC Corporation * Copyright (C) 2002 Miles Bader * * This file is subject to the terms and conditions of the GNU Lesser * General Public License. See the file COPYING.LIB in the main * directory of this archive for more details. * * Written by Miles Bader */ /* The alignment we guarantee for malloc return values. */ #define MALLOC_ALIGNMENT (sizeof (double)) /* The system pagesize we assume; we really ought to get it with getpagesize, but gee, how annoying. */ #define MALLOC_PAGE_SIZE 4096 /* The minimum size of block we request from the the system to extend the heap for small allocations (we may request a bigger block if necessary to satisfy a particularly big request). */ #define MALLOC_HEAP_EXTEND_SIZE MALLOC_PAGE_SIZE /* When a heap free-area grows above this size, try to unmap it, releasing the memory back to the system. */ #define MALLOC_UNMAP_THRESHOLD (8*MALLOC_PAGE_SIZE) /* When unmapping a free-area, retain this many bytes if it's the only one, to avoid completely emptying the heap. This is only a heuristic -- the existance of another free area, even if it's smaller than MALLOC_MIN_SIZE, will cause us not to reserve anything. */ #define MALLOC_MIN_SIZE (2*MALLOC_PAGE_SIZE) /* When realloc shrinks an allocation, it only does so if more than this many bytes will be freed; it must at at least HEAP_MIN_SIZE. Larger values increase speed (by reducing heap fragmentation) at the expense of space. */ #define MALLOC_REALLOC_MIN_FREE_SIZE (HEAP_MIN_SIZE + 16) /* For systems with an MMU, use sbrk to map/unmap memory for the malloc heap, instead of mmap/munmap. This is a tradeoff -- sbrk is faster than mmap/munmap, and guarantees contiguous allocation, but is also less flexible, and causes the heap to only be shrinkable from the end. */ #ifdef __UCLIBC_HAS_MMU__ # define MALLOC_USE_SBRK #endif /* The size of a malloc allocation is stored in a size_t word MALLOC_ALIGNMENT bytes prior to the start address of the allocation: +--------+---------+-------------------+ | SIZE |(unused) | allocation ... | +--------+---------+-------------------+ ^ BASE ^ ADDR ^ ADDR - MALLOC_ALIGN */ /* The amount of extra space used by the malloc header. */ #define MALLOC_HEADER_SIZE MALLOC_ALIGNMENT /* Set up the malloc header, and return the user address of a malloc block. */ #define MALLOC_SETUP(base, size) \ (MALLOC_SET_SIZE (base, size), (void *)((char *)base + MALLOC_HEADER_SIZE)) /* Set the size of a malloc allocation, given the base address. */ #define MALLOC_SET_SIZE(base, size) (*(size_t *)(base) = (size)) /* Return base-address of a malloc allocation, given the user address. */ #define MALLOC_BASE(addr) ((void *)((char *)addr - MALLOC_HEADER_SIZE)) /* Return the size of a malloc allocation, given the user address. */ #define MALLOC_SIZE(addr) (*(size_t *)MALLOC_BASE(addr)) /* Locking for multithreaded apps. */ #ifdef __UCLIBC_HAS_THREADS__ # include # define MALLOC_USE_LOCKING typedef pthread_mutex_t malloc_mutex_t; # define MALLOC_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER /* The main malloc lock. This must be hold while accessing __malloc_heap, and in order to gain __malloc_sbrk_lock. */ extern malloc_mutex_t __malloc_lock; # define __malloc_lock() pthread_mutex_lock (&__malloc_lock) # define __malloc_unlock() pthread_mutex_unlock (&__malloc_lock) # ifdef MALLOC_USE_SBRK /* This lock is used to serialize uses of the `sbrk' function (in both malloc and free, sbrk may be used several times in succession, and things will break if these multiple calls are interleaved with another thread's use of sbrk!). */ extern malloc_mutex_t __malloc_sbrk_lock; # define __malloc_lock_sbrk() pthread_mutex_lock (&__malloc_sbrk_lock) # define __malloc_unlock_sbrk() pthread_mutex_unlock (&__malloc_sbrk_lock) # endif /* MALLOC_USE_SBRK */ #else /* !__UCLIBC_HAS_THREADS__ */ /* Without threads, mutex operations are a nop. */ # define __malloc_lock() (void)0 # define __malloc_unlock() (void)0 # define __malloc_lock_sbrk() (void)0 # define __malloc_unlock_sbrk() (void)0 #endif /* __UCLIBC_HAS_THREADS__ */ /* branch-prediction macros; they may already be defined by libc. */ #ifndef likely #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96) #define likely(cond) __builtin_expect(!!(int)(cond), 1) #define unlikely(cond) __builtin_expect((int)(cond), 0) #else #define likely(cond) (cond) #define unlikely(cond) (cond) #endif #endif /* !likely */ /* Define MALLOC_DEBUGGING to cause malloc to emit debugging info to stderr. */ #ifdef MALLOC_DEBUGGING #include #define MALLOC_DEBUG(fmt, args...) fprintf (stderr, fmt , ##args) #else #define MALLOC_DEBUG(fmt, args...) (void)0 #endif /* Return SZ rounded down to POWER_OF_2_SIZE (which must be power of 2). */ #define MALLOC_ROUND_DOWN(sz, power_of_2_size) \ ((sz) & ~(power_of_2_size - 1)) /* Return SZ rounded to POWER_OF_2_SIZE (which must be power of 2). */ #define MALLOC_ROUND_UP(sz, power_of_2_size) \ MALLOC_ROUND_DOWN ((sz) + (power_of_2_size - 1), (power_of_2_size)) /* Return SZ rounded down to a multiple MALLOC_PAGE_SIZE. */ #define MALLOC_ROUND_DOWN_TO_PAGE_SIZE(sz) \ MALLOC_ROUND_DOWN (sz, MALLOC_PAGE_SIZE) /* Return SZ rounded up to a multiple MALLOC_PAGE_SIZE. */ #define MALLOC_ROUND_UP_TO_PAGE_SIZE(sz) \ MALLOC_ROUND_UP (sz, MALLOC_PAGE_SIZE) /* The malloc heap. */ extern struct heap __malloc_heap;