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+@comment !!! describe mmap et al (here?)
+@c !!! doc brk/sbrk
+
+@node Memory Allocation, Character Handling, Error Reporting, Top
+@chapter Memory Allocation
+@cindex memory allocation
+@cindex storage allocation
+
+The GNU system provides several methods for allocating memory space
+under explicit program control.  They vary in generality and in
+efficiency.
+
+@iftex
+@itemize @bullet
+@item
+The @code{malloc} facility allows fully general dynamic allocation.
+@xref{Unconstrained Allocation}.
+
+@item
+Obstacks are another facility, less general than @code{malloc} but more
+efficient and convenient for stacklike allocation.  @xref{Obstacks}.
+
+@item
+The function @code{alloca} lets you allocate storage dynamically that
+will be freed automatically.  @xref{Variable Size Automatic}.
+@end itemize
+@end iftex
+
+@menu
+* Memory Concepts::             An introduction to concepts and terminology.
+* Dynamic Allocation and C::    How to get different kinds of allocation in C.
+* Unconstrained Allocation::    The @code{malloc} facility allows fully general
+		 		 dynamic allocation.
+* Obstacks::                    Obstacks are less general than malloc
+				 but more efficient and convenient.
+* Variable Size Automatic::     Allocation of variable-sized blocks
+				 of automatic storage that are freed when the
+				 calling function returns.
+* Relocating Allocator::        Waste less memory, if you can tolerate
+				 automatic relocation of the blocks you get.
+* Memory Warnings::		Getting warnings when memory is nearly full.
+@end menu
+
+@node Memory Concepts
+@section Dynamic Memory Allocation Concepts
+@cindex dynamic allocation
+@cindex static allocation
+@cindex automatic allocation
+
+@dfn{Dynamic memory allocation} is a technique in which programs
+determine as they are running where to store some information.  You need
+dynamic allocation when the number of memory blocks you need, or how
+long you continue to need them, depends on the data you are working on.
+
+For example, you may need a block to store a line read from an input file;
+since there is no limit to how long a line can be, you must allocate the
+storage dynamically and make it dynamically larger as you read more of the
+line.
+
+Or, you may need a block for each record or each definition in the input
+data; since you can't know in advance how many there will be, you must
+allocate a new block for each record or definition as you read it.
+
+When you use dynamic allocation, the allocation of a block of memory is an
+action that the program requests explicitly.  You call a function or macro
+when you want to allocate space, and specify the size with an argument.  If
+you want to free the space, you do so by calling another function or macro.
+You can do these things whenever you want, as often as you want.
+
+@node Dynamic Allocation and C
+@section Dynamic Allocation and C
+
+The C language supports two kinds of memory allocation through the variables
+in C programs:
+
+@itemize @bullet
+@item
+@dfn{Static allocation} is what happens when you declare a static or
+global variable.  Each static or global variable defines one block of
+space, of a fixed size.  The space is allocated once, when your program
+is started, and is never freed.
+
+@item
+@dfn{Automatic allocation} happens when you declare an automatic
+variable, such as a function argument or a local variable.  The space
+for an automatic variable is allocated when the compound statement
+containing the declaration is entered, and is freed when that
+compound statement is exited.
+
+In GNU C, the length of the automatic storage can be an expression
+that varies.  In other C implementations, it must be a constant.
+@end itemize
+
+Dynamic allocation is not supported by C variables; there is no storage
+class ``dynamic'', and there can never be a C variable whose value is
+stored in dynamically allocated space.  The only way to refer to
+dynamically allocated space is through a pointer.  Because it is less
+convenient, and because the actual process of dynamic allocation
+requires more computation time, programmers generally use dynamic
+allocation only when neither static nor automatic allocation will serve.
+
+For example, if you want to allocate dynamically some space to hold a
+@code{struct foobar}, you cannot declare a variable of type @code{struct
+foobar} whose contents are the dynamically allocated space.  But you can
+declare a variable of pointer type @code{struct foobar *} and assign it the
+address of the space.  Then you can use the operators @samp{*} and
+@samp{->} on this pointer variable to refer to the contents of the space:
+
+@smallexample
+@{
+  struct foobar *ptr
+     = (struct foobar *) malloc (sizeof (struct foobar));
+  ptr->name = x;
+  ptr->next = current_foobar;
+  current_foobar = ptr;
+@}
+@end smallexample
+
+@node Unconstrained Allocation
+@section Unconstrained Allocation
+@cindex unconstrained storage allocation
+@cindex @code{malloc} function
+@cindex heap, dynamic allocation from
+
+The most general dynamic allocation facility is @code{malloc}.  It
+allows you to allocate blocks of memory of any size at any time, make
+them bigger or smaller at any time, and free the blocks individually at
+any time (or never).
+
+@menu
+* Basic Allocation::            Simple use of @code{malloc}.
+* Malloc Examples::             Examples of @code{malloc}.  @code{xmalloc}.
+* Freeing after Malloc::        Use @code{free} to free a block you
+				 got with @code{malloc}.
+* Changing Block Size::         Use @code{realloc} to make a block
+				 bigger or smaller.
+* Allocating Cleared Space::    Use @code{calloc} to allocate a
+				 block and clear it.
+* Efficiency and Malloc::       Efficiency considerations in use of
+				 these functions.
+* Aligned Memory Blocks::       Allocating specially aligned memory:
+				 @code{memalign} and @code{valloc}.
+* Heap Consistency Checking::   Automatic checking for errors.
+* Hooks for Malloc::            You can use these hooks for debugging
+				 programs that use @code{malloc}.
+* Statistics of Malloc::        Getting information about how much
+				 memory your program is using.
+* Summary of Malloc::           Summary of @code{malloc} and related functions.
+@end menu
+
+@node Basic Allocation
+@subsection Basic Storage Allocation
+@cindex allocation of memory with @code{malloc}
+
+To allocate a block of memory, call @code{malloc}.  The prototype for
+this function is in @file{stdlib.h}.
+@pindex stdlib.h
+
+@comment malloc.h stdlib.h
+@comment ANSI
+@deftypefun {void *} malloc (size_t @var{size})
+This function returns a pointer to a newly allocated block @var{size}
+bytes long, or a null pointer if the block could not be allocated.
+@end deftypefun
+
+The contents of the block are undefined; you must initialize it yourself
+(or use @code{calloc} instead; @pxref{Allocating Cleared Space}).
+Normally you would cast the value as a pointer to the kind of object
+that you want to store in the block.  Here we show an example of doing
+so, and of initializing the space with zeros using the library function
+@code{memset} (@pxref{Copying and Concatenation}):
+
+@smallexample
+struct foo *ptr;
+@dots{}
+ptr = (struct foo *) malloc (sizeof (struct foo));
+if (ptr == 0) abort ();
+memset (ptr, 0, sizeof (struct foo));
+@end smallexample
+
+You can store the result of @code{malloc} into any pointer variable
+without a cast, because ANSI C automatically converts the type
+@code{void *} to another type of pointer when necessary.  But the cast
+is necessary in contexts other than assignment operators or if you might
+want your code to run in traditional C.
+
+Remember that when allocating space for a string, the argument to
+@code{malloc} must be one plus the length of the string.  This is
+because a string is terminated with a null character that doesn't count
+in the ``length'' of the string but does need space.  For example:
+
+@smallexample
+char *ptr;
+@dots{}
+ptr = (char *) malloc (length + 1);
+@end smallexample
+
+@noindent
+@xref{Representation of Strings}, for more information about this.
+
+@node Malloc Examples
+@subsection Examples of @code{malloc}
+
+If no more space is available, @code{malloc} returns a null pointer.
+You should check the value of @emph{every} call to @code{malloc}.  It is
+useful to write a subroutine that calls @code{malloc} and reports an
+error if the value is a null pointer, returning only if the value is
+nonzero.  This function is conventionally called @code{xmalloc}.  Here
+it is:
+
+@smallexample
+void *
+xmalloc (size_t size)
+@{
+  register void *value = malloc (size);
+  if (value == 0)
+    fatal ("virtual memory exhausted");
+  return value;
+@}
+@end smallexample
+
+Here is a real example of using @code{malloc} (by way of @code{xmalloc}).
+The function @code{savestring} will copy a sequence of characters into
+a newly allocated null-terminated string:
+
+@smallexample
+@group
+char *
+savestring (const char *ptr, size_t len)
+@{
+  register char *value = (char *) xmalloc (len + 1);
+  memcpy (value, ptr, len);
+  value[len] = '\0';
+  return value;
+@}
+@end group
+@end smallexample
+
+The block that @code{malloc} gives you is guaranteed to be aligned so
+that it can hold any type of data.  In the GNU system, the address is
+always a multiple of eight; if the size of block is 16 or more, then the
+address is always a multiple of 16.  Only rarely is any higher boundary
+(such as a page boundary) necessary; for those cases, use
+@code{memalign} or @code{valloc} (@pxref{Aligned Memory Blocks}).
+
+Note that the memory located after the end of the block is likely to be
+in use for something else; perhaps a block already allocated by another
+call to @code{malloc}.  If you attempt to treat the block as longer than
+you asked for it to be, you are liable to destroy the data that
+@code{malloc} uses to keep track of its blocks, or you may destroy the
+contents of another block.  If you have already allocated a block and
+discover you want it to be bigger, use @code{realloc} (@pxref{Changing
+Block Size}).
+
+@node Freeing after Malloc
+@subsection Freeing Memory Allocated with @code{malloc}
+@cindex freeing memory allocated with @code{malloc}
+@cindex heap, freeing memory from
+
+When you no longer need a block that you got with @code{malloc}, use the
+function @code{free} to make the block available to be allocated again.
+The prototype for this function is in @file{stdlib.h}.
+@pindex stdlib.h
+
+@comment malloc.h stdlib.h
+@comment ANSI
+@deftypefun void free (void *@var{ptr})
+The @code{free} function deallocates the block of storage pointed at
+by @var{ptr}.
+@end deftypefun
+
+@comment stdlib.h
+@comment Sun
+@deftypefun void cfree (void *@var{ptr})
+This function does the same thing as @code{free}.  It's provided for
+backward compatibility with SunOS; you should use @code{free} instead.
+@end deftypefun
+
+Freeing a block alters the contents of the block.  @strong{Do not expect to
+find any data (such as a pointer to the next block in a chain of blocks) in
+the block after freeing it.}  Copy whatever you need out of the block before
+freeing it!  Here is an example of the proper way to free all the blocks in
+a chain, and the strings that they point to:
+
+@smallexample
+struct chain
+  @{
+    struct chain *next;
+    char *name;
+  @}
+
+void
+free_chain (struct chain *chain)
+@{
+  while (chain != 0)
+    @{
+      struct chain *next = chain->next;
+      free (chain->name);
+      free (chain);
+      chain = next;
+    @}
+@}
+@end smallexample
+
+Occasionally, @code{free} can actually return memory to the operating
+system and make the process smaller.  Usually, all it can do is allow a
+later call to @code{malloc} to reuse the space.  In the meantime, the
+space remains in your program as part of a free-list used internally by
+@code{malloc}.
+
+There is no point in freeing blocks at the end of a program, because all
+of the program's space is given back to the system when the process
+terminates.
+
+@node Changing Block Size
+@subsection Changing the Size of a Block
+@cindex changing the size of a block (@code{malloc})
+
+Often you do not know for certain how big a block you will ultimately need
+at the time you must begin to use the block.  For example, the block might
+be a buffer that you use to hold a line being read from a file; no matter
+how long you make the buffer initially, you may encounter a line that is
+longer.
+
+You can make the block longer by calling @code{realloc}.  This function
+is declared in @file{stdlib.h}.
+@pindex stdlib.h
+
+@comment malloc.h stdlib.h
+@comment ANSI
+@deftypefun {void *} realloc (void *@var{ptr}, size_t @var{newsize})
+The @code{realloc} function changes the size of the block whose address is
+@var{ptr} to be @var{newsize}.
+
+Since the space after the end of the block may be in use, @code{realloc}
+may find it necessary to copy the block to a new address where more free
+space is available.  The value of @code{realloc} is the new address of the
+block.  If the block needs to be moved, @code{realloc} copies the old
+contents.
+
+If you pass a null pointer for @var{ptr}, @code{realloc} behaves just
+like @samp{malloc (@var{newsize})}.  This can be convenient, but beware
+that older implementations (before ANSI C) may not support this
+behavior, and will probably crash when @code{realloc} is passed a null
+pointer.
+@end deftypefun
+
+Like @code{malloc}, @code{realloc} may return a null pointer if no
+memory space is available to make the block bigger.  When this happens,
+the original block is untouched; it has not been modified or relocated.
+
+In most cases it makes no difference what happens to the original block
+when @code{realloc} fails, because the application program cannot continue
+when it is out of memory, and the only thing to do is to give a fatal error
+message.  Often it is convenient to write and use a subroutine,
+conventionally called @code{xrealloc}, that takes care of the error message
+as @code{xmalloc} does for @code{malloc}:
+
+@smallexample
+void *
+xrealloc (void *ptr, size_t size)
+@{
+  register void *value = realloc (ptr, size);
+  if (value == 0)
+    fatal ("Virtual memory exhausted");
+  return value;
+@}
+@end smallexample
+
+You can also use @code{realloc} to make a block smaller.  The reason you
+would do this is to avoid tying up a lot of memory space when only a little
+is needed.  Making a block smaller sometimes necessitates copying it, so it
+can fail if no other space is available.
+
+If the new size you specify is the same as the old size, @code{realloc}
+is guaranteed to change nothing and return the same address that you gave.
+
+@node Allocating Cleared Space
+@subsection Allocating Cleared Space
+
+The function @code{calloc} allocates memory and clears it to zero.  It
+is declared in @file{stdlib.h}.
+@pindex stdlib.h
+
+@comment malloc.h stdlib.h
+@comment ANSI
+@deftypefun {void *} calloc (size_t @var{count}, size_t @var{eltsize})
+This function allocates a block long enough to contain a vector of
+@var{count} elements, each of size @var{eltsize}.  Its contents are
+cleared to zero before @code{calloc} returns.
+@end deftypefun
+
+You could define @code{calloc} as follows:
+
+@smallexample
+void *
+calloc (size_t count, size_t eltsize)
+@{
+  size_t size = count * eltsize;
+  void *value = malloc (size);
+  if (value != 0)
+    memset (value, 0, size);
+  return value;
+@}
+@end smallexample
+
+@node Efficiency and Malloc
+@subsection Efficiency Considerations for @code{malloc}
+@cindex efficiency and @code{malloc}
+
+To make the best use of @code{malloc}, it helps to know that the GNU
+version of @code{malloc} always dispenses small amounts of memory in
+blocks whose sizes are powers of two.  It keeps separate pools for each
+power of two.  This holds for sizes up to a page size.  Therefore, if
+you are free to choose the size of a small block in order to make
+@code{malloc} more efficient, make it a power of two.
+@c !!! xref getpagesize
+
+Once a page is split up for a particular block size, it can't be reused
+for another size unless all the blocks in it are freed.  In many
+programs, this is unlikely to happen.  Thus, you can sometimes make a
+program use memory more efficiently by using blocks of the same size for
+many different purposes.
+
+When you ask for memory blocks of a page or larger, @code{malloc} uses a
+different strategy; it rounds the size up to a multiple of a page, and
+it can coalesce and split blocks as needed.
+
+The reason for the two strategies is that it is important to allocate
+and free small blocks as fast as possible, but speed is less important
+for a large block since the program normally spends a fair amount of
+time using it.  Also, large blocks are normally fewer in number.
+Therefore, for large blocks, it makes sense to use a method which takes
+more time to minimize the wasted space.
+
+@node Aligned Memory Blocks
+@subsection Allocating Aligned Memory Blocks
+
+@cindex page boundary
+@cindex alignment (with @code{malloc})
+@pindex stdlib.h
+The address of a block returned by @code{malloc} or @code{realloc} in
+the GNU system is always a multiple of eight.  If you need a block whose
+address is a multiple of a higher power of two than that, use
+@code{memalign} or @code{valloc}.  These functions are declared in
+@file{stdlib.h}.
+
+With the GNU library, you can use @code{free} to free the blocks that
+@code{memalign} and @code{valloc} return.  That does not work in BSD,
+however---BSD does not provide any way to free such blocks.
+
+@comment malloc.h stdlib.h
+@comment BSD
+@deftypefun {void *} memalign (size_t @var{size}, size_t @var{boundary})
+The @code{memalign} function allocates a block of @var{size} bytes whose
+address is a multiple of @var{boundary}.  The @var{boundary} must be a
+power of two!  The function @code{memalign} works by calling
+@code{malloc} to allocate a somewhat larger block, and then returning an
+address within the block that is on the specified boundary.
+@end deftypefun
+
+@comment malloc.h stdlib.h
+@comment BSD
+@deftypefun {void *} valloc (size_t @var{size})
+Using @code{valloc} is like using @code{memalign} and passing the page size
+as the value of the second argument.  It is implemented like this:
+
+@smallexample
+void *
+valloc (size_t size)
+@{
+  return memalign (size, getpagesize ());
+@}
+@end smallexample
+@c !!! xref getpagesize
+@end deftypefun
+
+@node Heap Consistency Checking
+@subsection Heap Consistency Checking
+
+@cindex heap consistency checking
+@cindex consistency checking, of heap
+
+You can ask @code{malloc} to check the consistency of dynamic storage by
+using the @code{mcheck} function.  This function is a GNU extension,
+declared in @file{malloc.h}.
+@pindex malloc.h
+
+@comment malloc.h
+@comment GNU
+@deftypefun int mcheck (void (*@var{abortfn}) (enum mcheck_status @var{status}))
+Calling @code{mcheck} tells @code{malloc} to perform occasional
+consistency checks.  These will catch things such as writing
+past the end of a block that was allocated with @code{malloc}.
+
+The @var{abortfn} argument is the function to call when an inconsistency
+is found.  If you supply a null pointer, then @code{mcheck} uses a
+default function which prints a message and calls @code{abort}
+(@pxref{Aborting a Program}).  The function you supply is called with
+one argument, which says what sort of inconsistency was detected; its
+type is described below.
+
+It is too late to begin allocation checking once you have allocated
+anything with @code{malloc}.  So @code{mcheck} does nothing in that
+case.  The function returns @code{-1} if you call it too late, and
+@code{0} otherwise (when it is successful).
+
+The easiest way to arrange to call @code{mcheck} early enough is to use
+the option @samp{-lmcheck} when you link your program; then you don't
+need to modify your program source at all.
+@end deftypefun
+
+@deftypefun {enum mcheck_status} mprobe (void *@var{pointer})
+The @code{mprobe} function lets you explicitly check for inconsistencies
+in a particular allocated block.  You must have already called
+@code{mcheck} at the beginning of the program, to do its occasional
+checks; calling @code{mprobe} requests an additional consistency check
+to be done at the time of the call.
+
+The argument @var{pointer} must be a pointer returned by @code{malloc}
+or @code{realloc}.  @code{mprobe} returns a value that says what
+inconsistency, if any, was found.  The values are described below.
+@end deftypefun
+
+@deftp {Data Type} {enum mcheck_status}
+This enumerated type describes what kind of inconsistency was detected
+in an allocated block, if any.  Here are the possible values:
+
+@table @code
+@item MCHECK_DISABLED
+@code{mcheck} was not called before the first allocation.
+No consistency checking can be done.
+@item MCHECK_OK
+No inconsistency detected.
+@item MCHECK_HEAD
+The data immediately before the block was modified.
+This commonly happens when an array index or pointer
+is decremented too far.
+@item MCHECK_TAIL
+The data immediately after the block was modified.
+This commonly happens when an array index or pointer
+is incremented too far.
+@item MCHECK_FREE
+The block was already freed.
+@end table
+@end deftp
+
+@node Hooks for Malloc
+@subsection Storage Allocation Hooks
+@cindex allocation hooks, for @code{malloc}
+
+The GNU C library lets you modify the behavior of @code{malloc},
+@code{realloc}, and @code{free} by specifying appropriate hook
+functions.  You can use these hooks to help you debug programs that use
+dynamic storage allocation, for example.
+
+The hook variables are declared in @file{malloc.h}.
+@pindex malloc.h
+
+@comment malloc.h
+@comment GNU
+@defvar __malloc_hook
+The value of this variable is a pointer to function that @code{malloc}
+uses whenever it is called.  You should define this function to look
+like @code{malloc}; that is, like:
+
+@smallexample
+void *@var{function} (size_t @var{size})
+@end smallexample
+@end defvar
+
+@comment malloc.h
+@comment GNU
+@defvar __realloc_hook
+The value of this variable is a pointer to function that @code{realloc}
+uses whenever it is called.  You should define this function to look
+like @code{realloc}; that is, like:
+
+@smallexample
+void *@var{function} (void *@var{ptr}, size_t @var{size})
+@end smallexample
+@end defvar
+
+@comment malloc.h
+@comment GNU
+@defvar __free_hook
+The value of this variable is a pointer to function that @code{free}
+uses whenever it is called.  You should define this function to look
+like @code{free}; that is, like:
+
+@smallexample
+void @var{function} (void *@var{ptr})
+@end smallexample
+@end defvar
+
+You must make sure that the function you install as a hook for one of
+these functions does not call that function recursively without restoring
+the old value of the hook first!  Otherwise, your program will get stuck
+in an infinite recursion.
+
+Here is an example showing how to use @code{__malloc_hook} properly.  It
+installs a function that prints out information every time @code{malloc}
+is called.
+
+@smallexample
+static void *(*old_malloc_hook) (size_t);
+static void *
+my_malloc_hook (size_t size)
+@{
+  void *result;
+  __malloc_hook = old_malloc_hook;
+  result = malloc (size);
+  /* @r{@code{printf} might call @code{malloc}, so protect it too.} */
+  printf ("malloc (%u) returns %p\n", (unsigned int) size, result);
+  __malloc_hook = my_malloc_hook;
+  return result;
+@}
+
+main ()
+@{
+  ...
+  old_malloc_hook = __malloc_hook;
+  __malloc_hook = my_malloc_hook;
+  ...
+@}
+@end smallexample
+
+The @code{mcheck} function (@pxref{Heap Consistency Checking}) works by
+installing such hooks.
+
+@c __morecore, __after_morecore_hook are undocumented
+@c It's not clear whether to document them.
+
+@node Statistics of Malloc
+@subsection Statistics for Storage Allocation with @code{malloc}
+
+@cindex allocation statistics
+You can get information about dynamic storage allocation by calling the
+@code{mstats} function.  This function and its associated data type are
+declared in @file{malloc.h}; they are a GNU extension.
+@pindex malloc.h
+
+@comment malloc.h
+@comment GNU
+@deftp {Data Type} {struct mstats}
+This structure type is used to return information about the dynamic
+storage allocator.  It contains the following members:
+
+@table @code
+@item size_t bytes_total
+This is the total size of memory managed by @code{malloc}, in bytes.
+
+@item size_t chunks_used
+This is the number of chunks in use.  (The storage a