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Sync/libc/include/stdlib.h
Jessica Creighton 3fe2d7aa33 Format files
2019-04-03 17:46:58 -04:00

595 lines
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C
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#ifndef _STDLIB_H
#define _STDLIB_H 1
#include <sys/cdefs.h>
__attribute__((__noreturn__)) void abort(void);
/*
Default header file for malloc-2.8.x, written by Doug Lea
and released to the public domain, as explained at
http://creativecommons.org/publicdomain/zero/1.0/
This header is for ANSI C/C++ only. You can set any of
the following #defines before including:
* If USE_DL_PREFIX is defined, it is assumed that malloc.c
was also compiled with this option, so all routines
have names starting with "dl".
* If HAVE_USR_INCLUDE_MALLOC_H is defined, it is assumed that this
file will be #included AFTER <malloc.h>. This is needed only if
your system defines a struct mallinfo that is incompatible with the
standard one declared here. Otherwise, you can include this file
INSTEAD of your system system <malloc.h>. At least on ANSI, all
declarations should be compatible with system versions
* If MSPACES is defined, declarations for mspace versions are included.
*/
#ifdef __cplusplus
extern "C" {
#endif
#include <stddef.h> /* for size_t */
#ifndef ONLY_MSPACES
#define ONLY_MSPACES 0 /* define to a value */
#elif ONLY_MSPACES != 0
#define ONLY_MSPACES 1
#endif /* ONLY_MSPACES */
#ifndef NO_MALLINFO
#define NO_MALLINFO 0
#endif /* NO_MALLINFO */
#ifndef MSPACES
#if ONLY_MSPACES
#define MSPACES 1
#else /* ONLY_MSPACES */
#define MSPACES 0
#endif /* ONLY_MSPACES */
#endif /* MSPACES */
#if !ONLY_MSPACES
#if !NO_MALLINFO
#ifndef HAVE_USR_INCLUDE_MALLOC_H
#ifndef _MALLOC_H
#ifndef MALLINFO_FIELD_TYPE
#define MALLINFO_FIELD_TYPE size_t
#endif /* MALLINFO_FIELD_TYPE */
#ifndef STRUCT_MALLINFO_DECLARED
#define STRUCT_MALLINFO_DECLARED 1
struct mallinfo {
MALLINFO_FIELD_TYPE arena; /* non-mmapped space allocated from system */
MALLINFO_FIELD_TYPE ordblks; /* number of free chunks */
MALLINFO_FIELD_TYPE smblks; /* always 0 */
MALLINFO_FIELD_TYPE hblks; /* always 0 */
MALLINFO_FIELD_TYPE hblkhd; /* space in mmapped regions */
MALLINFO_FIELD_TYPE usmblks; /* maximum total allocated space */
MALLINFO_FIELD_TYPE fsmblks; /* always 0 */
MALLINFO_FIELD_TYPE uordblks; /* total allocated space */
MALLINFO_FIELD_TYPE fordblks; /* total free space */
MALLINFO_FIELD_TYPE keepcost; /* releasable (via malloc_trim) space */
};
#endif /* STRUCT_MALLINFO_DECLARED */
#endif /* _MALLOC_H */
#endif /* HAVE_USR_INCLUDE_MALLOC_H */
#endif /* !NO_MALLINFO */
/*
malloc(size_t n)
Returns a pointer to a newly allocated chunk of at least n bytes, or
null if no space is available, in which case errno is set to ENOMEM
on ANSI C systems.
If n is zero, malloc returns a minimum-sized chunk. (The minimum
size is 16 bytes on most 32bit systems, and 32 bytes on 64bit
systems.) Note that size_t is an unsigned type, so calls with
arguments that would be negative if signed are interpreted as
requests for huge amounts of space, which will often fail. The
maximum supported value of n differs across systems, but is in all
cases less than the maximum representable value of a size_t.
*/
void* malloc(size_t);
/*
free(void* p)
Releases the chunk of memory pointed to by p, that had been previously
allocated using malloc or a related routine such as realloc.
It has no effect if p is null. If p was not malloced or already
freed, free(p) will by default cuase the current program to abort.
*/
void free(void*);
/*
calloc(size_t n_elements, size_t element_size);
Returns a pointer to n_elements * element_size bytes, with all locations
set to zero.
*/
void* calloc(size_t, size_t);
/*
realloc(void* p, size_t n)
Returns a pointer to a chunk of size n that contains the same data
as does chunk p up to the minimum of (n, p's size) bytes, or null
if no space is available.
The returned pointer may or may not be the same as p. The algorithm
prefers extending p in most cases when possible, otherwise it
employs the equivalent of a malloc-copy-free sequence.
If p is null, realloc is equivalent to malloc.
If space is not available, realloc returns null, errno is set (if on
ANSI) and p is NOT freed.
if n is for fewer bytes than already held by p, the newly unused
space is lopped off and freed if possible. realloc with a size
argument of zero (re)allocates a minimum-sized chunk.
The old unix realloc convention of allowing the last-free'd chunk
to be used as an argument to realloc is not supported.
*/
void* realloc(void*, size_t);
/*
realloc_in_place(void* p, size_t n)
Resizes the space allocated for p to size n, only if this can be
done without moving p (i.e., only if there is adjacent space
available if n is greater than p's current allocated size, or n is
less than or equal to p's size). This may be used instead of plain
realloc if an alternative allocation strategy is needed upon failure
to expand space; for example, reallocation of a buffer that must be
memory-aligned or cleared. You can use realloc_in_place to trigger
these alternatives only when needed.
Returns p if successful; otherwise null.
*/
void* realloc_in_place(void*, size_t);
/*
memalign(size_t alignment, size_t n);
Returns a pointer to a newly allocated chunk of n bytes, aligned
in accord with the alignment argument.
The alignment argument should be a power of two. If the argument is
not a power of two, the nearest greater power is used.
8-byte alignment is guaranteed by normal malloc calls, so don't
bother calling memalign with an argument of 8 or less.
Overreliance on memalign is a sure way to fragment space.
*/
void* memalign(size_t, size_t);
/*
int posix_memalign(void** pp, size_t alignment, size_t n);
Allocates a chunk of n bytes, aligned in accord with the alignment
argument. Differs from memalign only in that it (1) assigns the
allocated memory to *pp rather than returning it, (2) fails and
returns EINVAL if the alignment is not a power of two (3) fails and
returns ENOMEM if memory cannot be allocated.
*/
int posix_memalign(void**, size_t, size_t);
/*
valloc(size_t n);
Equivalent to memalign(pagesize, n), where pagesize is the page
size of the system. If the pagesize is unknown, 4096 is used.
*/
void* valloc(size_t);
/*
mallopt(int parameter_number, int parameter_value)
Sets tunable parameters The format is to provide a
(parameter-number, parameter-value) pair. mallopt then sets the
corresponding parameter to the argument value if it can (i.e., so
long as the value is meaningful), and returns 1 if successful else
0. SVID/XPG/ANSI defines four standard param numbers for mallopt,
normally defined in malloc.h. None of these are use in this malloc,
so setting them has no effect. But this malloc also supports other
options in mallopt:
Symbol param # default allowed param values
M_TRIM_THRESHOLD -1 2*1024*1024 any (-1U disables trimming)
M_GRANULARITY -2 page size any power of 2 >= page size
M_MMAP_THRESHOLD -3 256*1024 any (or 0 if no MMAP support)
*/
int mallopt(int, int);
#define M_TRIM_THRESHOLD (-1)
#define M_GRANULARITY (-2)
#define M_MMAP_THRESHOLD (-3)
/*
malloc_footprint();
Returns the number of bytes obtained from the system. The total
number of bytes allocated by malloc, realloc etc., is less than this
value. Unlike mallinfo, this function returns only a precomputed
result, so can be called frequently to monitor memory consumption.
Even if locks are otherwise defined, this function does not use them,
so results might not be up to date.
*/
size_t malloc_footprint(void);
/*
malloc_max_footprint();
Returns the maximum number of bytes obtained from the system. This
value will be greater than current footprint if deallocated space
has been reclaimed by the system. The peak number of bytes allocated
by malloc, realloc etc., is less than this value. Unlike mallinfo,
this function returns only a precomputed result, so can be called
frequently to monitor memory consumption. Even if locks are
otherwise defined, this function does not use them, so results might
not be up to date.
*/
size_t malloc_max_footprint(void);
/*
malloc_footprint_limit();
Returns the number of bytes that the heap is allowed to obtain from
the system, returning the last value returned by
malloc_set_footprint_limit, or the maximum size_t value if
never set. The returned value reflects a permission. There is no
guarantee that this number of bytes can actually be obtained from
the system.
*/
size_t malloc_footprint_limit(void);
/*
malloc_set_footprint_limit();
Sets the maximum number of bytes to obtain from the system, causing
failure returns from malloc and related functions upon attempts to
exceed this value. The argument value may be subject to page
rounding to an enforceable limit; this actual value is returned.
Using an argument of the maximum possible size_t effectively
disables checks. If the argument is less than or equal to the
current malloc_footprint, then all future allocations that require
additional system memory will fail. However, invocation cannot
retroactively deallocate existing used memory.
*/
size_t malloc_set_footprint_limit(size_t bytes);
/*
malloc_inspect_all(void(*handler)(void *start,
void *end,
size_t used_bytes,
void* callback_arg),
void* arg);
Traverses the heap and calls the given handler for each managed
region, skipping all bytes that are (or may be) used for bookkeeping
purposes. Traversal does not include include chunks that have been
directly memory mapped. Each reported region begins at the start
address, and continues up to but not including the end address. The
first used_bytes of the region contain allocated data. If
used_bytes is zero, the region is unallocated. The handler is
invoked with the given callback argument. If locks are defined, they
are held during the entire traversal. It is a bad idea to invoke
other malloc functions from within the handler.
For example, to count the number of in-use chunks with size greater
than 1000, you could write:
static int count = 0;
void count_chunks(void* start, void* end, size_t used, void* arg) {
if (used >= 1000) ++count;
}
then:
malloc_inspect_all(count_chunks, NULL);
malloc_inspect_all is compiled only if MALLOC_INSPECT_ALL is defined.
*/
void malloc_inspect_all(void (*handler)(void*, void*, size_t, void*), void* arg);
#if !NO_MALLINFO
/*
mallinfo()
Returns (by copy) a struct containing various summary statistics:
arena: current total non-mmapped bytes allocated from system
ordblks: the number of free chunks
smblks: always zero.
hblks: current number of mmapped regions
hblkhd: total bytes held in mmapped regions
usmblks: the maximum total allocated space. This will be greater
than current total if trimming has occurred.
fsmblks: always zero
uordblks: current total allocated space (normal or mmapped)
fordblks: total free space
keepcost: the maximum number of bytes that could ideally be released
back to system via malloc_trim. ("ideally" means that
it ignores page restrictions etc.)
Because these fields are ints, but internal bookkeeping may
be kept as longs, the reported values may wrap around zero and
thus be inaccurate.
*/
struct mallinfo mallinfo(void);
#endif /* NO_MALLINFO */
/*
independent_calloc(size_t n_elements, size_t element_size, void* chunks[]);
independent_calloc is similar to calloc, but instead of returning a
single cleared space, it returns an array of pointers to n_elements
independent elements that can hold contents of size elem_size, each
of which starts out cleared, and can be independently freed,
realloc'ed etc. The elements are guaranteed to be adjacently
allocated (this is not guaranteed to occur with multiple callocs or
mallocs), which may also improve cache locality in some
applications.
The "chunks" argument is optional (i.e., may be null, which is
probably the most typical usage). If it is null, the returned array
is itself dynamically allocated and should also be freed when it is
no longer needed. Otherwise, the chunks array must be of at least
n_elements in length. It is filled in with the pointers to the
chunks.
In either case, independent_calloc returns this pointer array, or
null if the allocation failed. If n_elements is zero and "chunks"
is null, it returns a chunk representing an array with zero elements
(which should be freed if not wanted).
Each element must be freed when it is no longer needed. This can be
done all at once using bulk_free.
independent_calloc simplifies and speeds up implementations of many
kinds of pools. It may also be useful when constructing large data
structures that initially have a fixed number of fixed-sized nodes,
but the number is not known at compile time, and some of the nodes
may later need to be freed. For example:
struct Node { int item; struct Node* next; };
struct Node* build_list() {
struct Node** pool;
int n = read_number_of_nodes_needed();
if (n <= 0) return 0;
pool = (struct Node**)(independent_calloc(n, sizeof(struct Node), 0);
if (pool == 0) die();
// organize into a linked list...
struct Node* first = pool[0];
for (i = 0; i < n-1; ++i)
pool[i]->next = pool[i+1];
free(pool); // Can now free the array (or not, if it is needed later)
return first;
}
*/
void** independent_calloc(size_t, size_t, void**);
/*
independent_comalloc(size_t n_elements, size_t sizes[], void* chunks[]);
independent_comalloc allocates, all at once, a set of n_elements
chunks with sizes indicated in the "sizes" array. It returns
an array of pointers to these elements, each of which can be
independently freed, realloc'ed etc. The elements are guaranteed to
be adjacently allocated (this is not guaranteed to occur with
multiple callocs or mallocs), which may also improve cache locality
in some applications.
The "chunks" argument is optional (i.e., may be null). If it is null
the returned array is itself dynamically allocated and should also
be freed when it is no longer needed. Otherwise, the chunks array
must be of at least n_elements in length. It is filled in with the
pointers to the chunks.
In either case, independent_comalloc returns this pointer array, or
null if the allocation failed. If n_elements is zero and chunks is
null, it returns a chunk representing an array with zero elements
(which should be freed if not wanted).
Each element must be freed when it is no longer needed. This can be
done all at once using bulk_free.
independent_comallac differs from independent_calloc in that each
element may have a different size, and also that it does not
automatically clear elements.
independent_comalloc can be used to speed up allocation in cases
where several structs or objects must always be allocated at the
same time. For example:
struct Head { ... }
struct Foot { ... }
void send_message(char* msg) {
int msglen = strlen(msg);
size_t sizes[3] = { sizeof(struct Head), msglen, sizeof(struct Foot) };
void* chunks[3];
if (independent_comalloc(3, sizes, chunks) == 0)
die();
struct Head* head = (struct Head*)(chunks[0]);
char* body = (char*)(chunks[1]);
struct Foot* foot = (struct Foot*)(chunks[2]);
// ...
}
In general though, independent_comalloc is worth using only for
larger values of n_elements. For small values, you probably won't
detect enough difference from series of malloc calls to bother.
Overuse of independent_comalloc can increase overall memory usage,
since it cannot reuse existing noncontiguous small chunks that
might be available for some of the elements.
*/
void** independent_comalloc(size_t, size_t*, void**);
/*
bulk_free(void* array[], size_t n_elements)
Frees and clears (sets to null) each non-null pointer in the given
array. This is likely to be faster than freeing them one-by-one.
If footers are used, pointers that have been allocated in different
mspaces are not freed or cleared, and the count of all such pointers
is returned. For large arrays of pointers with poor locality, it
may be worthwhile to sort this array before calling bulk_free.
*/
size_t bulk_free(void**, size_t n_elements);
/*
pvalloc(size_t n);
Equivalent to valloc(minimum-page-that-holds(n)), that is,
round up n to nearest pagesize.
*/
void* pvalloc(size_t);
/*
malloc_trim(size_t pad);
If possible, gives memory back to the system (via negative arguments
to sbrk) if there is unused memory at the `high' end of the malloc
pool or in unused MMAP segments. You can call this after freeing
large blocks of memory to potentially reduce the system-level memory
requirements of a program. However, it cannot guarantee to reduce
memory. Under some allocation patterns, some large free blocks of
memory will be locked between two used chunks, so they cannot be
given back to the system.
The `pad' argument to malloc_trim represents the amount of free
trailing space to leave untrimmed. If this argument is zero, only
the minimum amount of memory to maintain internal data structures
will be left. Non-zero arguments can be supplied to maintain enough
trailing space to service future expected allocations without having
to re-obtain memory from the system.
Malloc_trim returns 1 if it actually released any memory, else 0.
*/
int malloc_trim(size_t);
/*
malloc_stats();
Prints on stderr the amount of space obtained from the system (both
via sbrk and mmap), the maximum amount (which may be more than
current if malloc_trim and/or munmap got called), and the current
number of bytes allocated via malloc (or realloc, etc) but not yet
freed. Note that this is the number of bytes allocated, not the
number requested. It will be larger than the number requested
because of alignment and bookkeeping overhead. Because it includes
alignment wastage as being in use, this figure may be greater than
zero even when no user-level chunks are allocated.
The reported current and maximum system memory can be inaccurate if
a program makes other calls to system memory allocation functions
(normally sbrk) outside of malloc.
malloc_stats prints only the most commonly interesting statistics.
More information can be obtained by calling mallinfo.
malloc_stats is not compiled if NO_MALLOC_STATS is defined.
*/
void malloc_stats(void);
#endif /* !ONLY_MSPACES */
/*
malloc_usable_size(void* p);
Returns the number of bytes you can actually use in
an allocated chunk, which may be more than you requested (although
often not) due to alignment and minimum size constraints.
You can use this many bytes without worrying about
overwriting other allocated objects. This is not a particularly great
programming practice. malloc_usable_size can be more useful in
debugging and assertions, for example:
p = malloc(n);
assert(malloc_usable_size(p) >= 256);
*/
size_t malloc_usable_size(const void*);
#if MSPACES
/*
mspace is an opaque type representing an independent
region of space that supports mspace_malloc, etc.
*/
typedef void* mspace;
/*
create_mspace creates and returns a new independent space with the
given initial capacity, or, if 0, the default granularity size. It
returns null if there is no system memory available to create the
space. If argument locked is non-zero, the space uses a separate
lock to control access. The capacity of the space will grow
dynamically as needed to service mspace_malloc requests. You can
control the sizes of incremental increases of this space by
compiling with a different DEFAULT_GRANULARITY or dynamically
setting with mallopt(M_GRANULARITY, value).
*/
mspace create_mspace(size_t capacity, int locked);
/*
destroy_mspace destroys the given space, and attempts to return all
of its memory back to the system, returning the total number of
bytes freed. After destruction, the results of access to all memory
used by the space become undefined.
*/
size_t destroy_mspace(mspace msp);
/*
create_mspace_with_base uses the memory supplied as the initial base
of a new mspace. Part (less than 128*sizeof(size_t) bytes) of this
space is used for bookkeeping, so the capacity must be at least this
large. (Otherwise 0 is returned.) When this initial space is
exhausted, additional memory will be obtained from the system.
Destroying this space will deallocate all additionally allocated
space (if possible) but not the initial base.
*/
mspace create_mspace_with_base(void* base, size_t capacity, int locked);
/*
mspace_track_large_chunks controls whether requests for large chunks
are allocated in their own untracked mmapped regions, separate from
others in this mspace. By default large chunks are not tracked,
which reduces fragmentation. However, such chunks are not
necessarily released to the system upon destroy_mspace. Enabling
tracking by setting to true may increase fragmentation, but avoids
leakage when relying on destroy_mspace to release all memory
allocated using this space. The function returns the previous
setting.
*/
int mspace_track_large_chunks(mspace msp, int enable);
#if !NO_MALLINFO
/*
mspace_mallinfo behaves as mallinfo, but reports properties of
the given space.
*/
struct mallinfo mspace_mallinfo(mspace msp);
#endif /* NO_MALLINFO */
/*
An alias for mallopt.
*/
int mspace_mallopt(int, int);
/*
The following operate identically to their malloc counterparts
but operate only for the given mspace argument
*/
void* mspace_malloc(mspace msp, size_t bytes);
void mspace_free(mspace msp, void* mem);
void* mspace_calloc(mspace msp, size_t n_elements, size_t elem_size);
void* mspace_realloc(mspace msp, void* mem, size_t newsize);
void* mspace_realloc_in_place(mspace msp, void* mem, size_t newsize);
void* mspace_memalign(mspace msp, size_t alignment, size_t bytes);
void** mspace_independent_calloc(mspace msp, size_t n_elements, size_t elem_size, void* chunks[]);
void** mspace_independent_comalloc(mspace msp, size_t n_elements, size_t sizes[], void* chunks[]);
size_t mspace_bulk_free(mspace msp, void**, size_t n_elements);
size_t mspace_usable_size(const void* mem);
void mspace_malloc_stats(mspace msp);
int mspace_trim(mspace msp, size_t pad);
size_t mspace_footprint(mspace msp);
size_t mspace_max_footprint(mspace msp);
size_t mspace_footprint_limit(mspace msp);
size_t mspace_set_footprint_limit(mspace msp, size_t bytes);
void mspace_inspect_all(mspace msp, void (*handler)(void*, void*, size_t, void*), void* arg);
#endif /* MSPACES */
#ifdef __cplusplus
}; /* end of extern "C" */
#endif
#endif /* MALLOC_280_H */
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