2 * libc/stdlib/malloc/malloc.h -- small malloc implementation
4 * Copyright (C) 2002 NEC Corporation
5 * Copyright (C) 2002 Miles Bader <miles@gnu.org>
7 * This file is subject to the terms and conditions of the GNU Lesser
8 * General Public License. See the file COPYING.LIB in the main
9 * directory of this archive for more details.
11 * Written by Miles Bader <miles@gnu.org>
14 /* The alignment we guarantee for malloc return values. We prefer this
15 to be at least sizeof (size_t) bytes because (a) we have to allocate
16 that many bytes for the header anyway and (b) guaranteeing word
17 alignment can be a significant win on targets like m68k and Coldfire,
18 where __alignof__(double) == 2. */
19 #define MALLOC_ALIGNMENT \
20 __alignof__ (double __attribute_aligned__ (sizeof (size_t)))
22 /* The system pagesize... */
23 extern size_t __pagesize;
24 #define MALLOC_PAGE_SIZE __pagesize
26 /* The minimum size of block we request from the the system to extend the
27 heap for small allocations (we may request a bigger block if necessary to
28 satisfy a particularly big request). */
29 #define MALLOC_HEAP_EXTEND_SIZE MALLOC_PAGE_SIZE
31 /* When a heap free-area grows above this size, try to unmap it, releasing
32 the memory back to the system. */
33 #define MALLOC_UNMAP_THRESHOLD (8*MALLOC_PAGE_SIZE)
34 /* When unmapping a free-area, retain this many bytes if it's the only one,
35 to avoid completely emptying the heap. This is only a heuristic -- the
36 existance of another free area, even if it's smaller than
37 MALLOC_MIN_SIZE, will cause us not to reserve anything. */
38 #define MALLOC_MIN_SIZE (2*MALLOC_PAGE_SIZE)
40 /* When realloc shrinks an allocation, it only does so if more than this
41 many bytes will be freed; it must at at least HEAP_MIN_SIZE. Larger
42 values increase speed (by reducing heap fragmentation) at the expense of
44 #define MALLOC_REALLOC_MIN_FREE_SIZE (HEAP_MIN_SIZE + 16)
47 /* For systems with an MMU, use sbrk to map/unmap memory for the malloc
48 heap, instead of mmap/munmap. This is a tradeoff -- sbrk is faster than
49 mmap/munmap, and guarantees contiguous allocation, but is also less
50 flexible, and causes the heap to only be shrinkable from the end. */
51 #ifdef __ARCH_USE_MMU__
52 # define MALLOC_USE_SBRK
55 /* FM3: sbrk not implemented */
56 #undef MALLOC_USE_SBRK
57 /* make sure that we munmap areas with the same size we mmapped */
58 #define __UCLIBC_UCLINUX_BROKEN_MUNMAP__
61 /* The current implementation of munmap in uClinux doesn't work correctly:
62 it requires that ever call to munmap exactly match a corresponding call
63 to mmap (that is, it doesn't allow you to unmap only part of a
64 previously allocated block, or to unmap two contiguous blocks with a
65 single call to munmap). This behavior is broken, and uClinux should be
66 fixed; however, until it is, we add code to work around the problem in
68 #ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__
70 /* A structure recording a block of memory mmapped by malloc. */
73 void *mem; /* the mmapped block */
74 size_t size; /* its size */
75 struct malloc_mmb *next;
78 /* A list of all malloc_mmb structures describing blocks that malloc has
79 mmapped, ordered by the block address. */
80 extern struct malloc_mmb *__malloc_mmapped_blocks;
82 /* A heap used for allocating malloc_mmb structures. We could allocate
83 them from the main heap, but that tends to cause heap fragmentation in
85 extern struct heap_free_area *__malloc_mmb_heap;
87 /* Define MALLOC_MMB_DEBUGGING to cause malloc to emit debugging info about
88 about mmap block allocation/freeing by the `uclinux broken munmap' code
89 to stderr, when the variable __malloc_mmb_debug is set to true. */
90 #ifdef MALLOC_MMB_DEBUGGING
93 extern int __malloc_mmb_debug;
94 # define MALLOC_MMB_DEBUG(indent, fmt, args...) \
95 (__malloc_mmb_debug ? __malloc_debug_printf (indent, fmt , ##args) : 0)
96 # define MALLOC_MMB_DEBUG_INDENT(indent) \
97 (__malloc_mmb_debug ? __malloc_debug_indent (indent) : 0)
98 # ifndef MALLOC_DEBUGGING
99 # define MALLOC_DEBUGGING
101 #else /* !MALLOC_MMB_DEBUGGING */
102 # define MALLOC_MMB_DEBUG(fmt, args...) (void)0
103 # define MALLOC_MMB_DEBUG_INDENT(indent) (void)0
104 #endif /* MALLOC_MMB_DEBUGGING */
106 #endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */
109 /* The size of a malloc allocation is stored in a size_t word
110 MALLOC_HEADER_SIZE bytes prior to the start address of the allocation:
112 +--------+---------+-------------------+
113 | SIZE |(unused) | allocation ... |
114 +--------+---------+-------------------+
116 ^ ADDR - MALLOC_HEADER_SIZE
119 /* The amount of extra space used by the malloc header. */
120 #define MALLOC_HEADER_SIZE \
121 (MALLOC_ALIGNMENT < sizeof (size_t) \
125 /* Set up the malloc header, and return the user address of a malloc block. */
126 #define MALLOC_SETUP(base, size) \
127 (MALLOC_SET_SIZE (base, size), (void *)((char *)base + MALLOC_HEADER_SIZE))
128 /* Set the size of a malloc allocation, given the base address. */
129 #define MALLOC_SET_SIZE(base, size) (*(size_t *)(base) = (size))
131 /* Return base-address of a malloc allocation, given the user address. */
132 #define MALLOC_BASE(addr) ((void *)((char *)addr - MALLOC_HEADER_SIZE))
133 /* Return the size of a malloc allocation, given the user address. */
134 #define MALLOC_SIZE(addr) (*(size_t *)MALLOC_BASE(addr))
137 /* Locking for multithreaded apps. */
138 #ifdef __UCLIBC_HAS_THREADS__
140 # include <pthread.h>
141 # include <bits/uClibc_pthread.h>
143 # define MALLOC_USE_LOCKING
145 typedef pthread_mutex_t malloc_mutex_t;
146 # define MALLOC_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
148 # ifdef MALLOC_USE_SBRK
149 /* This lock is used to serialize uses of the `sbrk' function (in both
150 malloc and free, sbrk may be used several times in succession, and
151 things will break if these multiple calls are interleaved with another
152 thread's use of sbrk!). */
153 extern malloc_mutex_t __malloc_sbrk_lock;
154 # define __malloc_lock_sbrk() __pthread_mutex_lock (&__malloc_sbrk_lock)
155 # define __malloc_unlock_sbrk() __pthread_mutex_unlock (&__malloc_sbrk_lock)
156 # endif /* MALLOC_USE_SBRK */
158 #else /* !__UCLIBC_HAS_THREADS__ */
160 /* Without threads, mutex operations are a nop. */
161 # define __malloc_lock_sbrk() (void)0
162 # define __malloc_unlock_sbrk() (void)0
164 #endif /* __UCLIBC_HAS_THREADS__ */
167 /* branch-prediction macros; they may already be defined by libc. */
169 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
170 #define likely(cond) __builtin_expect(!!(int)(cond), 1)
171 #define unlikely(cond) __builtin_expect((int)(cond), 0)
173 #define likely(cond) (cond)
174 #define unlikely(cond) (cond)
179 /* Define MALLOC_DEBUGGING to cause malloc to emit debugging info to stderr
180 when the variable __malloc_debug is set to true. */
181 #ifdef MALLOC_DEBUGGING
183 extern void __malloc_debug_init (void);
185 /* The number of spaces in a malloc debug indent level. */
186 #define MALLOC_DEBUG_INDENT_SIZE 3
188 extern int __malloc_debug, __malloc_check;
190 # define MALLOC_DEBUG(indent, fmt, args...) \
191 (__malloc_debug ? __malloc_debug_printf (indent, fmt , ##args) : 0)
192 # define MALLOC_DEBUG_INDENT(indent) \
193 (__malloc_debug ? __malloc_debug_indent (indent) : 0)
195 extern int __malloc_debug_cur_indent;
197 /* Print FMT and args indented at the current debug print level, followed
198 by a newline, and change the level by INDENT. */
199 extern void __malloc_debug_printf (int indent, const char *fmt, ...);
201 /* Change the current debug print level by INDENT, and return the value. */
202 #define __malloc_debug_indent(indent) (__malloc_debug_cur_indent += indent)
204 /* Set the current debug print level to LEVEL. */
205 #define __malloc_debug_set_indent(level) (__malloc_debug_cur_indent = level)
207 #else /* !MALLOC_DEBUGGING */
208 # define MALLOC_DEBUG(fmt, args...) (void)0
209 # define MALLOC_DEBUG_INDENT(indent) (void)0
210 #endif /* MALLOC_DEBUGGING */
213 /* Return SZ rounded down to POWER_OF_2_SIZE (which must be power of 2). */
214 #define MALLOC_ROUND_DOWN(sz, power_of_2_size) \
215 ((sz) & ~(power_of_2_size - 1))
216 /* Return SZ rounded to POWER_OF_2_SIZE (which must be power of 2). */
217 #define MALLOC_ROUND_UP(sz, power_of_2_size) \
218 MALLOC_ROUND_DOWN ((sz) + (power_of_2_size - 1), (power_of_2_size))
220 /* Return SZ rounded down to a multiple MALLOC_PAGE_SIZE. */
221 #define MALLOC_ROUND_DOWN_TO_PAGE_SIZE(sz) \
222 MALLOC_ROUND_DOWN (sz, MALLOC_PAGE_SIZE)
223 /* Return SZ rounded up to a multiple MALLOC_PAGE_SIZE. */
224 #define MALLOC_ROUND_UP_TO_PAGE_SIZE(sz) \
225 MALLOC_ROUND_UP (sz, MALLOC_PAGE_SIZE)
228 /* The malloc heap. */
229 extern struct heap_free_area *__malloc_heap;
230 #ifdef __UCLIBC_HAS_THREADS__
231 extern malloc_mutex_t __malloc_heap_lock;
232 #ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__
233 extern malloc_mutex_t __malloc_mmb_heap_lock;